Knee
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nOITCeS
part of the tibial tuberosity and skin; and a large suprapatellar bursa, extension, i.e. they are obligatory. They can also be adjunct and inde-
which is the superior extension of the knee joint cavity (see Fig. 82.16). pendent, i.e. voluntary, and are best demonstrated with the knee semi-
Posterolaterally, there are bursae between the lateral head of gastrocne- flexed. The degree of axial rotation therefore varies with flexion and
mius (lateral subtendinous bursa of gastrocnemius) and the joint extension.
capsule (this bursa is sometimes continuous with the joint cavity); the The range of extension is 5–10° beyond the ‘straight position’. Active
fibular collateral ligament and the tendon of biceps femoris; the fibular flexion is approximately 120° with the hip extended, 140° when it is
collateral ligament and the tendon of popliteus; and the tendon of flexed, and 160° when aided by a passive element, e.g. sitting on the
popliteus and the lateral femoral condyle, which is usually an extension heels. Voluntary rotation is 60–70° but conjunct rotation only 20°.
of the synovial cavity of the joint. The last two bursae may communicate Conjunct medial rotation of the femur on the tibia in the later stages
with each other. of extension is part of a ‘locking’ mechanism, the so-called ‘screw-home
Medially, the arrangement of the bursae is complex. The bursa movement’, which is an asset when the fully extended knees are sub-
between the medial head of gastrocnemius and the fibrous capsule is jected to strain. Full extension results in the close-packed position, with
prolonged between the medial tendon of gastrocnemius and the tendon maximal spiralization and tightening of the ligaments. The roles of the
of semimembranosus (the semimembranosus bursa), and usually com- articular surfaces, musculature and ligaments in generating conjunct
municates with the joint. The bursa between the tendon of semimem- rotations remain controversial (Girgis et al 1975, Rajendran 1985) but


branosus and the medial tibial condyle and the medial head of the following points can be made. The lateral combined meniscotibial
gastrocnemius may communicate with this bursa. The anserine bursa ‘receiving surface’ is smaller, more circular and more deeply concave.
is located between the tibial collateral ligament and the tendons of Since the articular surface is virtually convex in sagittal section, the
sartorius, gracilis and semitendinosus. Bursae that vary in both number depth of the receiving surface is largely due to the presence of the lateral
and position lie deep to the tibial collateral ligament between the joint meniscus. The lateral femoral articular surface is also smaller. Conse-
capsule, femur, medial meniscus, tibia or tendon of semimembranosus. quently, the lateral femoral condyle approaches full congruence with
Occasionally, there may be a bursa between the tendons of semimem- the opposed surface some 30° before full extension (well before the
branosus and semitendinosus. Posteriorly, bursae associated with the medial condyle). Simple extension cannot continue, but medial rota-
knee are variable. tion of the femur occurs on a vertical axis through its head and medial
The clinically important bursae are the anterior group, the anserine condyle; the medial femoral condyle moves very little in the sagittal
bursa and the semimembranosus bursa. Inflammation of the subcuta- plane and is stabilized by the ‘upslope’ of the anterior half of the medial
neous prepatellar bursa and infrapatellar bursa are referred to colloqui- tibia, while rotation of the lateral femoral condyle and meniscus brings
ally as ‘housemaid’s knee’ and ‘clergyman’s knee’, respectively. The the anterior horn of the latter on to the anterior ‘downslope’ of the
anserine bursa can become inflamed, especially in athletes. In adults, lateral tibial condyle. Rotation and extension follow simultaneously
bursal inflammation producing a popliteal fossa swelling commonly and smoothly until final close packing of both condyles is accom-
occurs secondary to degeneration within the knee joint; regardless plished. At the beginning of flexion from full extension (with the foot


of its size and position, it almost always arises from the plane fixed), lateral femoral rotation occurs, which ‘unlocks’ the joint. While
between semimembranosus and the tendon of the medial head of joint surfaces and many ligaments are involved, electromyographic evi-
gastrocnemius. dence reveals that contraction of popliteus is important, and that it
pulls down and backwards on the lateral femoral condyle, lateral to the
Relations and ‘at risk’ structures axis of femoral rotation. It also retracts the posterior horn during lateral
rotation and continuing flexion, via its attachment to the lateral menis-
cus, and so prevents traumatic compression.
The tendon of quadriceps femoris (which encloses and is attached to
Any position of extension adopted is a balance between forces
the non-articular surfaces of the patella), the patellar ligament, tendi-
(torque) extending the joint and passive mechanisms resisting them.
nous expansions from vasti medialis and lateralis (which extend over
The range near to close packing is functionally important. In symmetri-
the anteromedial and anterolateral aspects of the capsule, respectively),
cal standing, the line of the body’s weight is anterior to the transverse
and the patellar retinacula all lie anterior to the knee joint. Postero-
axes of the knee joints, but the passive mechanisms noted above pre-
medially are sartorius and the tendon of gracilis (which lies along its
serve posture with minimal muscular effort (Joseph 1960). Active con-
posterior border); both descend across the joint. Posterolaterally, the
traction of quadriceps femoris and a close-packed position only occurs
tendon of biceps femoris and the common fibular nerve (which lies
in asymmetrical postures, e.g. in leaning forward, during heavy loading,
medial to the tendon) are in contact with the capsule, and thereby
or when powerful thrust is needed.
separated from the tendon of popliteus. Posteriorly, the popliteal artery
In knee extension, parts of the cruciate ligaments, the tibial and
and associated lymph nodes lie posterior to the oblique popliteal liga-
fibular collateral ligaments, the posterior capsular region, the oblique
ment; the popliteal vein is posteromedial or medial, and the tibial nerve


popliteal ligament, skin and fasciae are all taut. Passive and sometimes
is posterior to both. The nerve and vessels are overlapped by both heads
active tension exists in the posterior thigh muscles and gastrocnemius,
of gastrocnemius and laterally by plantaris. Gastrocnemius contacts the
and the anterior part of the medial meniscus is compressed between
capsules on either side of the vessels. Semimembranosus lies between
the femoral and tibial condyles. During extension, the patellar ligament
the capsule and semitendinosus, medial to the medial head of
is tightened by quadriceps femoris but is relaxed in the erect attitude.
gastrocnemius.
When the knee flexes, the fibular collateral ligament and the posterior
part of the tibial collateral ligament relax but the cruciate ligaments and
Movements at the knee
the anterior part of the tibial collateral ligament remain taut; the pos-
terior parts of the menisci are compressed between the femoral and
Movements at the knee are customarily described as flexion, extension, tibial condyles. Flexion is checked by quadriceps femoris, anterior parts
medial (internal) and lateral (external) rotation. Flexion and extension of the knee joint capsule, posterior cruciate ligament and compression
differ from true hingeing, in that the articular surface profiles of the of soft tissues behind the knee. In extreme passive flexion, contact of
femoral and tibial articular surfaces produce a variably placed axis of the calf with the thigh may be the limiting factor and parts of both
rotation during the flexion arc, and when the foot is fixed, flexion cruciate ligaments are also taut. In addition to conjunct rotation with
entails corresponding conjunct (coupled) lateral rotation. These con- terminal extension or initial flexion, relaxed collateral ligaments also
junct rotations are a product of the complex geometry of the articular allow independent medial and lateral rotation (adjunct rotation) when
surfaces and, to an extent, the disposition of the associated ligaments. the joint is flexed.
There is differential motion in the medial and lateral tibiofemoral
compartments. Laterally, there is considerable displacement of the Accessory movements
femur on the tibia, with rolling as well as sliding at the joint surface. Wider rotation can be obtained by passive movements when the knee


In contrast, medially, for most of the flexion arc there is minimal rela- is semi-flexed. To a limited extent, the tibia can also be translated back-
tive motion of the femur and tibia, and the motion almost exclusively wards and forwards on the femur. Abduction and adduction are pre-
involves one joint surface sliding on the other. In full flexion, the lateral vented in full extension by the collateral ligaments and secondary
femoral condyle is close to posterior subluxation off the lateral tibial restraints such as the cruciate ligaments. With the knee slightly flexed,
articular surface. Medially, significant posterior femoral displacement limited adduction and abduction are possible, both passive and active.
only occurs when flexion exceeds 120°. The menisci move with the Slight separation of the femur and tibia can be achieved by strong trac-
femoral condyles, the anterior horns more than the posterior, and the tion on the leg with countertraction applied to the thigh.
lateral meniscus considerably more than the medial. Physiological knee joint laxity may occur during puberty. Increased
The axial rotations have a smaller range than the arc of flexion and knee joint flexibility is seen more frequently in adolescent girls than
extension. These rotations are conjunct, and integral with flexion and boys. There is an inverse relationship between Tanner stage and the


Biomechanics of the knee
1393
28
ReTPAHC
degree of laxity with a progressive decrease of sagittal laxity at the onset generated by activities such as running, the patella has the thickest
of Tanner stage 2 (Falciglia et al 2009). articular cartilage in the body.
Muscles producing movements
Flexion Flexion is produced by biceps femoris, semitendinosus and BIOMECHANICS OF THE KNEE
semimembranosus, assisted by gracilis, sartorius and popliteus. With
the foot stationary, gastrocnemius and plantaris also assist (see Fig. The knee joint is a complex synovial joint consisting of the tibiofemoral
82.3). and patellofemoral articulations. It functions to control the centre of
body mass and posture in the activities of daily living. This necessitates
Extension Extension is produced by quadriceps femoris, assisted by a large range of movement in three dimensions coupled with the ability
tensor fasciae latae. to withstand high forces. These conflicting parameters of mobility and
stability are only achieved by the interactions between the articular
Medial rotation of the flexed leg Medial rotation of the flexed surfaces, the passive stabilizers and the muscles that cross the joint.
leg is produced by popliteus, semimembranosus and semitendinosus, The relatively incongruent nature of the joint surfaces makes the
assisted by sartorius and gracilis. knee joint inherently mobile. In addition, because it acts as a pivot
between the longest bones in the body, and is subjected to considerable
Lateral rotation of the flexed leg Lateral rotation of the flexed loads in locomotion, the joint is also potentially at risk of injury if any
leg is produced by biceps femoris. of the multiple factors providing joint stability are compromised. The
long bones may act as levers, increasing the stresses on the stabilizing
Patellofemoral joint The alignment of the femoral and tibial shafts ligaments.
is such that the pull of quadriceps femoris on the patella imparts a force
on the patella that is directed both superiorly and laterally. The static
bony factors that counter this tendency to move laterally are the congru- KNEE JOINT KINEMATICS


ity of the patellofemoral joint and the buttressing effect of the larger
lateral part of the patellar surface of the femur, which, clinically, is often The surfaces of the tibia and femur are not as conforming as those of
referred to as the trochlear groove. Instability of the patella may result the relatively congruent hip joint. Although this variation in geometry
if the patella is small or if the patellar surface of the femur is too permits motion to occur in six degrees of freedom (Fig. 82.18), the
shallow. The static ligamentous factors are the medial patellofemoral primary motion of the knee occurs in the sagittal plane, and a relatively
ligament and medial patellar retinaculum. minor degree of movement occurs in the transverse plane. The knee
Dynamic neuromuscular control is important. The most distal part joint may therefore be described simplistically as a modified hinge joint
of vastus medialis (vastus medialis obliquus) consists of transverse allowing flexion–extension and a measure of rotatory motion. Knee
fibres that are attached directly to the medial edge of the patella: these motion is normally defined as starting from 0° (the neutral position),
pull the patella medially, countering the tendency to move laterally. when the tibia and femur are in line in the sagittal plane. Biomechani-
This is the muscle that is preferentially strengthened in a physical cally, it is important that the knee reaches the neutral position in exten-
therapy programme aimed at treating patellofemoral conditions often sion because that allows the leg to support the body weight like a simple
associated with patella tracking problems such as those seen in growing strut when the subject is standing still. When the subject is standing
adolescents. upright, if the knee is flexed, the vertical line of action of the body
weight passes posterior to the centre of rotation of the knee, tending to
Tibiofemoral joint The tibiofemoral joint surfaces are inherently cause the body to tilt posteriorly. To counterbalance this, continuous
mobile, especially laterally. Medially, some stability is afforded by the quadriceps femoris contraction is required, causing expenditure of
relatively concave tibial surface and the relatively fixed posterior horn energy.


of the medial meniscus. Both medially and laterally the menisci are
helpful, particularly as they move with the femoral condyles. Ligaments Anterior/posterior translation Medial/lateral shift Compression/distraction
play a major role in constraining mobility because they bind the bones
in positions of extreme stress and also provide proprioceptive feedback,
aiding coordination of stabilizing muscle activity. To take a somewhat
‘two-dimensional’ view, the tibial and fibular collateral ligaments may
be considered as sensors (resistors) of valgus and varus forces on the
knee, respectively, and the anterior and posterior cruciate ligaments as
sensors (resistors) of anterior and posterior tibial translation, respec-
tively. However, in reality the situation is more complex than this. The
stresses are rarely applied in orthogonal planes and so a combination
of forces, especially rotational, is involved. Moreover, many structures
other than the collateral and cruciate ligaments are involved in stabiliz-
ing the joint. The ‘posterolateral corner’, which resists tibial lateral
rotation, consists of the popliteofibular, fabellofibular, arcuate and
fibular collateral ligaments and iliotibial tract, together with popliteus,
the lateral head of gastrocnemius and biceps femoris. The ‘postero-
medial corner’, which resists tibial rotation, consists of the posterior
oblique portion of the superficial part of the tibial collateral ligament, Abduction/adduction Flexion/extension Medial/lateral rotation
the capsule including the oblique popliteal ligament and semimem-
branosus. Since stresses are often a combination of force plus rotation,
structures usually operate together rather than in isolation.
Loading at the knee
During level walking, the force across the tibiofemoral joint for most
of the cycle is between two and four times body weight, and can be
more. In contrast, the force across the patellofemoral joint is no more
than 50% of body weight. Peak force transmission across the joint
increases sequentially as the menisci, articular cartilage and subchon-
dral bone are damaged or removed. Walking up or down stairs has little
influence on tibiofemoral forces, but significantly increases patellofem-


oral forces to two (walking up) or three (walking down) times body
weight, reflecting the changed angle of the tendon of quadriceps femoris
and patellar ligament during flexion. There are two mechanisms for
ameliorating forces transmitted across the patella: the extensor lever
arm is lengthened as the axis of rotation moves posteriorly during
flexion, and the contact area between the patella and femur almost Fig. 82.18 The knee joint motion in three dimensions, described using six
triples between 30° and 90°. To cope with the potential large forces independent variables (degrees of freedom).


Knee
1394
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nOITCeS
Active knee flexion leads to approximately 130° flexion. The active the geometry and tighten the soft tissues, thereby maintaining the knee
motion is limited by apposition of the soft tissue masses (posterior in a stable position prior to the impact load of weight-bearing. The knee
thigh and calf). Passive flexion may reach 160°. This is required in acts as one link in a chain of limb segments, and this screw-home relates
people who habitually kneel as part of daily life, and is a challenge for to rotation of both the foot and hip. When the foot is swung forwards
designers of knee prostheses. It can be observed that such deep flexion for heel strike, the pelvis rotates so that the hip is moved forwards, a
is often accompanied by tibial medial rotation, so that, when the movement that entails lateral rotation of the hip. During stance, the
subject is kneeling, the buttocks can rest on the feet. This movement femur is medially rotated against the locked knee. Tibial lateral rotation
carries the lateral tibial plateau anteriorly, so that it does not engage also causes inversion of the foot at the subtalar joint, raising the arch
with the femoral lateral condyle in deep knee flexion. The femoral and locking the structure of the foot. The knee flexion that occurs after
condyle passes posteriorly and rides over the horn of the lateral the impact on the ground allows the tibia to rotate medially so that the
meniscus. foot everts, softening its structure and allowing it to deform and absorb
The most frequently employed knee movement occurs when walking energy. Conversely, towards toe-off, the knee extends, rotating the tibia
(Fig. 82.19). When the leg is swinging past the supporting leg, the knee laterally, so the foot is again a rigid lever with which to push the body
must be flexed in order to avoid dragging the toes on the ground; this forwards.
requires approximately 67° knee flexion. When the swinging leg
Articular kinematics
approaches the first contact with the ground, the knee extends, to move
the foot forwards for heel strike. If the knee remained extended, this We now consider knee motion at a smaller scale, within the joint. This,


would then cause the body to move in a circular arc, centred at the of course, is difficult to separate from the actions of the ligaments that
ankle, causing the centre of gravity to move upwards and then back act as passive restraints to tibiofemoral joint movements, and are dis-
down again, leading to more energy expenditure. It would also increase cussed below.
the forces on the knee because the leg would act more like a rigid strut, Sagittal sections of the knee reveal that the arcs of the femoral con-
unable to dissipate the impact forces when the foot hit the ground. All dyles are much longer than the anterior–posterior length of the tibial
these problems are overcome by flexing the knee 15° in the mid-stance plateau. This means that if the knee flexed with a purely rolling motion,
phase; the centre of gravity of the body can move forwards at approxi- then the femur would roll off the back of the tibia long before the knee
mately constant height, and the impact energy is absorbed by stretching reaches full flexion (see Fig. 82.20). This does not happen because the
quadriceps femoris (see Fig. 82.19). femur slides anteriorly at the same time as it rolls posteriorly, and thus
Tibial medial–lateral rotation also occurs during gait: the tibia remains in correct articulation. If the knee were to possess a fully con-
rotates laterally during terminal extension, a phenomenon known as forming roller-in-trough geometry, as in the humero-ulnar joint, then
‘screw-home’ (Fig. 82.20). It is surmised that this rotation helps to lock flexion would occur by pure sliding movement between the joint
Fig. 82.19 Knee flexion–extension motion during gait.
)º(
noixelf
tnioj
eenK
Contralateral
Heel strike heel strike Toe-off
60
30
20
0
0 10 20 30 40 50 60 70 80 90 100
% Gait cycle
A B C Fig. 82.20 Knee joint kinematics during gait:
rolling and sliding (flexion, anterior translation).
Rolling
F F
F
1
2 Anterior cruciate
3 2 1 3 2 1 3 ligament
Tension
Sliding


2 1 2 1 2 1
T T T
Extension: Early flexion: Deeper flexion:
Central contact Posterior rolling. Anterior cruciate
of femur on to tibia Contact now ligament prevents
(F1 on to T1) moves back to the femur from rolling
F2 on to T2 back further, so now
it slides on the tibia.
F3 moves on to T2


Biomechanics of the knee
1395
28
ReTPAHC
surfaces. This conformity is not possible at the knee because it would anterior horns of the menisci, and the femoral contact is now solely on
inhibit the tibial medial–lateral rotation that is needed during the posterior horns in the flexed knee. This, combined with the large
locomotion. joint forces that are generated when arising from a seated position,
In the locked, fully extended knee, the anterodistal femoral articular explains why there are often spontaneous tears of the posterior horns
surfaces press on to the anterior horns of the menisci. This tends to in older patients, when standing up from a squatting position.
cause the femur to slide posteriorly, tensing the anterior cruciate liga- The load-carrying mode of the menisci is shown in Figure 82.23.
ment and slackening the posterior cruciate ligament. With knee flexion, When the femoral condyle presses down on the meniscus, it tends to
the femur lifts off the anterior horns of the menisci, leading to contact squeeze the meniscus out of the joint because of its tapered cross-
between the smaller radii of the posterior parts of the femoral condyles section. This causes the diameter of the circular shape of the meniscus
and the tibial plateau plus the posterior horns of the menisci. This (and therefore the meniscal circumference) to increase. This is resisted
means that the centre of contact moves posteriorly in early knee flexion. by ‘hoop tension’ in strong fibres that pass around the periphery of the
After this, the femoral condyles have approximately circular sagittal meniscus, and transmit the tension to the tibial plateau via strong
sections. The femur is now prevented from rolling back any further by insertional ligaments. As the tissue is adapted to resist hoop stresses, it
tension in the anterior cruciate ligament. has much greater hoop strength (approximately 100 MPa) than radial
strength (approximately 3 MPa), which explains why bucket handle
Articular mechanics
tears occur. It also explains why a circumferential tear does not have
The combined effect of the external and internal loads on the knee is such a serious effect on meniscal function because the circumferential


to impose considerable forces on the articular cartilage. This may be fibres can still transmit the loads, whereas a radial tear breaks the load-
analysed as a vertical (compressive) component and a horizontal (shear carrying fibres.
or friction) component. The friction component is a combination of
the compressive force and the friction characteristics of the joint Friction
surfaces. The knee acts as a bearing that transmits forces and movements between
the limb segments. Load-bearing synovial joints move with remarkably
Compression
little friction and their surfaces must withstand many millions of impact
The compressive force is distributed over an area to produce a contact loads, which tend to cause fatigue failure and breakdown of the
pressure (contact stress). The contact pressure is, therefore, dependent surfaces.
on the area of contact as well as the load itself. Fully conforming articu- During walking, every step involves phases of action that vary the
lar surface geometry would allow the greatest area of contact, and thus loading and velocity conditions at the knee joint. A variety of lubrica-
would minimize contact pressure; however, this is not present in the tion mechanisms normally prevent joint surface damage. Thus, in the
knee. The medial compartment of the knee is semi-conforming with a swing phase, when the foot is off the ground, the joint surfaces are
convex femoral condyle articulating over a concave medial tibial
plateau. The lateral compartment has less conformity; the lateral tibial
plateau is flat or slightly convex in sagittal sections. These different
shapes reflect the differential movement of the medial and lateral com-
partments. In normal movement, the screw-home rotation of the tibia
occurs about a medial axis, which means that most of the rotation of
the tibia is due to an anterior–posterior translation of the lateral com-
partment (Fig. 82.21).
In order to maintain some degree of conformity, and also to mini-
mize contact pressure between the femur and tibia, the menisci are
wedge-shaped in cross-section, thereby increasing the area over which
the compressive force on the knee is distributed. In the absence of the
menisci, the load is carried by a much smaller area of cartilage, resulting
in higher contact stresses on the articular cartilage. This helps to explain
the prevalence of osteoarthrosis following meniscectomy (Fig. 82.22).


The menisci are most firmly attached at the intercondylar eminence
of the tibia, which means that they can translate anteriorly and pos-
teriorly to ‘follow’ the femoral rollback. The lateral meniscus is more
mobile because it is attached to the capsule less tightly than the medial
meniscus. The anterior–posterior movement of the menisci is approxi-
mately half the magnitude of the anterior–posterior movement of the
femur, suggesting that the conformity of the joint changes during
flexion of the knee joint.
The distal aspect of the femur, resting on the menisci in the extended
knee, has a large radius of curvature and thus fits against the entire area
of the menisci. However, as the knee flexes, the smaller radii of the
posterior parts of the femoral condyles cause the femur to lift off the
Fig. 82.22 The function of the menisci in increasing articular conformity,
Medial compartment Lateral compartment with increased peak pressure before and after meniscectomy.
Medial pivot in concave
tibial plateau
Mobile lateral
compartment
Concave tibial plateau Convex/flat tibial plateau
(congruent) (incongruent)
Fig. 82.21 The shape of the articular surfaces providing mobility of the Fig. 82.23 The load-carrying mode of the menisci. Conversion of axial
lateral compartment. load into meniscal hoop stresses.


Knee
1396
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nOITCeS
Swing phase Heel strike Stance phase Toe-off
Muscle Muscle
tension tension
Flexion/
extension
Rapid
motion
Impact Body weight
Load
Femur
Fluid
trapped
Tibia
Fluid film Squeeze film: Hydrodynamic lubrication: Squeeze film with protein
fluid squeezed out, cartilage surface deforms, boundary lubricant
microscopic separation trapping fluid film
remains
Fig. 82.24 The different modes of knee joint motion and lubrication when walking.
loaded lightly, and have high relative velocity while the knee flexes and displacement and allow the joint to maintain its stability. Disruption
extends. This allows the synovial fluid to separate the surfaces, giving of any of these passive restraints may cause a mechanical instability,
fluid film lubrication, with very low friction and no wear (Fig. 82.24). which is an abnormally increased displacement due to an applied force
At the time of heel strike, a large impact load acts to compress the (in biomechanical terms this is called excess laxity).
surfaces together. At a microscopic level, the surfaces do not come into
Primary and secondary restraints
contact because of the squeeze-film effect: in essence, the impact occurs
so rapidly (less than 0.1 sec) that the synovial fluid cannot all be On testing the laxity in any of the degrees of freedom of the joint (e.g.
squeezed out of the joint space because of its viscosity and the narrow- in the anterior drawer test, a bedside clinical test in which the subject
ness of the space. In the mid-stance phase, the flexion–extension motion is placed in the supine position with the knee to be tested flexed to
again entrains the synovial fluid in between the joint surfaces, prod- 80–90° before passive forward traction is applied to the tibia), there
ucing what is known as a hydrodynamic effect: the fluid is trapped are usually combinations of ligaments that are tensed. Some of these
between the surfaces by the motion and therefore it acts to separate are better aligned to resist the applied load or displacement. These are
them. Finally, when the foot is pushing off the body weight, there is termed primary restraints, and are exemplified by the cruciate ligaments


little motion and the thin fluid film diminishes under the compressive and the tibial and fibular collateral ligaments. Secondary restraints are
load. If the squeeze-film effect were insufficient, then the joint surfaces less well aligned but still have a significant restraining effect. These are
would come into direct contact were it not for the fact that the synovial exemplified by the menisci and by the meniscofemoral ligaments. In
fluid contains large protein molecules that are trapped on the cartilage the example in Figure 82.25, the anterior cruciate ligament is well
surfaces when the fluid is expelled. This molecular layer acts as a bound- aligned to resist the applied anterior force. With an absent anterior
ary lubricant, protecting the cartilage in the same way that grease pro- cruciate ligament, the tibial collateral ligament can resist the applied
tects a synthetic bearing. force; however, it does so by being loaded to a much higher level than
Many aspects of the arthritic breakdown of the cartilage can be the original loading on the anterior cruciate ligament. The size of the
explained on the basis of lubrication biomechanics. Thus, in joints lines in the vector diagram demonstrate this principle: although joint
affected by osteoarthrosis, synovial fluid is known to have a lower vis- laxity may remain normal initially following rupture of a primary
cosity than that in normal joints. The viscosity is lower still in joints restraint, it may subsequently result in the overload of a secondary
afflicted with rheumatoid arthritis and is unable to prevent attritional restraint and, ultimately, in further soft tissue failure.
damage to the cartilage surfaces. The patellofemoral joint is most heavily loaded during weight-
bearing activities when the knee is flexed. Analyses of rising from a chair
have predicted that the patellar ligament tension at 90° of knee flexion
SOFT TISSUE MECHANICS may be greater than the tibiofemoral joint, which is loaded at the same
time (Amis and Farahmand 1996).
The knee joint relies on active (musculotendinous) and passive (liga- In the frontal plane, quadriceps femoris and the patellar ligament
mentous) restraints to maintain its stability. The muscles provide the tensions combine to cause a lateralizing force vector termed the Q-angle


loading to move the joint: quadriceps femoris, hamstrings and gastroc- effect. The Q angle is defined as the difference between the resultant
nemius control both flexion/extension and medial–lateral rotation. force vector of quadriceps femoris, which is normally parallel to the
However, they also cause anterior–posterior shear forces that are resisted femoral shaft, and the patellar ligament (Fig. 82.26). Clinically, the Q
primarily by the cruciate ligaments. This tethering effect is critical in angle is changed by the position of hip rotation, tibial rotation and
allowing the joint to move physiologically, maintaining congruency quadriceps femoris tension. The clinical Q angle is 12–15° (males) and
and stability. 15–18° (females), which means that there is a greater lateralizing force
The passive stabilizers of the joint act by resisting unwanted displace- vector on the patellofemoral joint in females. Contraction of quadriceps
ments between the bones. This may be to control the path of motion femoris, therefore, tends to displace the patella laterally, which is
or to limit the range of motion. When the muscles or some other exter- resisted by the geometry of the joint and by the ligaments. Vastus
nal force (due to body weight or impact) cause the bones to displace, medialis obliquus acts medially and posteriorly as much as it acts
the ligaments are stretched, and so develop tensile forces that resist the proximally, and so its tension helps to resist the Q-angle effect.


Vascular supply and lymphatic drainage
1397
28
ReTPAHC
Popliteus is attached to the medial aspect of the head of the fibula
by the popliteofibular ligament, which passes laterally and inferiorly
from the popliteus tendon in a sheet of tissue that is normally about
2 cm2. This ligament is the single most important stabilizer of the pos-
terolateral region of the knee and resists lateral rotation of the tibia on
the femur. Failure to recognize and reconstruct damage to this ligament
Applied force
and to the related ligamentous structures is the most common reason
for a poor result from an otherwise well-performed operation for repair
ACL vector of ruptured cruciate ligaments.
Fleshy fibres expand from the inferior limit of the tendon to form a
Anterior cruciate ligament (ACL)
somewhat triangular muscle that descends medially to be inserted into
the medial two-thirds of the triangular area above the soleal line on the
posterior surface of the tibia, and into the tendinous expansion that
covers its surface.
An additional head may arise from the sesamoid bone in the lateral
head of gastrocnemius. Very rarely, two other muscles may be found
deeply situated behind the knee. Popliteus minor runs from the pos-
terior surface of the lateral tibial condyle, medial to plantaris, to the
oblique popliteal ligament. Peroneotibialis runs deep to popliteus
from the medial side of the fibular head to the upper end of the
soleal line.
Relations Popliteus is covered posteriorly by a dense aponeurotic
expansion, which is largely derived from the tendon of semimembrano-
Applied force
sus. Gastrocnemius, plantaris, the popliteal vessels and the tibial nerve
all lie posterior to the expansion. The popliteal tendon is intracapsular
and is deep to the fibular collateral ligament and the tendon of biceps
Superficial tibial femoris. It is invested on its deep surface by synovial membrane, and
collateral ligament (sTCL)
grooves the posterior border of the lateral meniscus and the adjoining
part of the tibia before it emerges inferior to the posterior band of the
sTCL vector arcuate ligament. This region is called the ‘popliteus hiatus’; the lateral


meniscus has no peripheral bony attachment here and is therefore
rather mobile.
Vascular supply The arterial supply of popliteus is derived mainly
Fig. 82.25 Primary and secondary restraints to anteroposterior forces. from the inferior medial and lateral genicular arteries. The latter may
The example shows the anterior cruciate ligament (ACL) and superficial cross either superficial or deep to the muscle. There are additional con-
part of the tibial collateral ligament (sTCL). tributions from the nutrient artery of the tibia (from the posterior tibial
artery), the proximal part of the posterior tibial artery, and the posterior
tibial recurrent artery.
A Q B
Q
Innervation Popliteus is innervated by a branch of the tibial nerve
(L4, 5 and S1), which winds around the distal border of popliteus and
enters the anterior surface of the muscle; this nerve also innervates
the superior tibiofibular joint and the interosseous membrane of
PF
the leg.
PL
PF
Actions Popliteus rotates the tibia medially on the femur or, when
PL the tibia is fixed, rotates the femur laterally on the tibia. It is usually
regarded as the muscle that ‘unlocks’ the joint at the beginning of
flexion of the fully extended knee; electromyography supports this view.
Its connection with the arcuate popliteal ligament, fibrous capsule and
PL lateral meniscus has led to the suggestion that popliteus may retract the
Q
posterior horn of the lateral meniscus during lateral rotation of the
Q PL PL femur and flexion of the knee joint, thus protecting the meniscus from
PL being crushed between the femur and the tibia during these move-
ments. The muscle is markedly active in crouching, perhaps to provide
PL = Patellar ligament force PF = Patellofemoral joint reaction force Q = Quadriceps
femoris traction force stability as the tibia rotates medially during flexion of the knee. However,
the main function is likely to be provision of dynamic stability to the
Fig. 82.26 The patellofemoral joint force with knee extension (A) and with
posterolateral part of the knee by preventing excessive lateral rotation
90° of knee flexion (B).


of the tibia, partly by its direct action, but more significantly by tensing
the popliteofibular ligament.
MUSCLES
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
The majority of muscles that act on the knee joint are described in either
ARTERIES
Chapter 80 (quadriceps femoris, semimembranosus, biceps femoris,
semitendinosus, articularis genus) or on page 1409 (gastrocnemius).
Popliteus is described below. There is an intricate arterial anastomosis around the patella and the
femoral and tibial condyles (see Fig. 78.4). A superficial arterial network
Popliteus spreads between the fascia and skin around the patella and in the fat
Attachments Popliteus is a flat muscle that forms the floor of the deep to the patellar ligament. A deep arterial network lies on the femur
lower part of the popliteal fossa (see Figs 82.12A, 83.4B, 83.9A). It arises and tibia near the adjoining articular surfaces, and supplies the bone,
within the capsule of the knee joint by a strong tendon, 2.5 cm long, articular capsule, synovial membrane and cruciate ligaments (see Fig.
which is attached to a depression at the anterior end of the groove 82.1). The vessels involved are the superior, middle and inferior genicu-
(groove for popliteus) on the lateral aspect of the lateral condyle of the lar branches of the popliteal artery; descending genicular branches of
femur. Medially, this tendon is joined by collagenous fibres arising from the femoral artery and descending branch of the lateral circumflex
the arcuate popliteal ligament; the fibrous capsule adjacent to the lateral femoral artery; circumflex fibular artery; and anterior and posterior
meniscus; and the outer margin of the meniscus. tibial recurrent arteries. For details, consult Scapinelli (1968).


Knee
1398
9
nOITCeS
Variations in the arterial anatomy of the lower limb proximal to the medial head of gastrocnemius and deep to the tendon
Most anatomical variations in the arterial pattern of the lower limb of adductor magnus. It divides into a branch to vastus medialis that
arteries cause no symptoms. They are usually incidental findings in the anastomoses with the descending genicular and inferior medial genicu-
dissection room, or may come to light in the course of angiographic lar arteries, and a branch that ramifies on the femur and anastomoses
examination. Some variations in vascular anatomy may be symptomatic with the superior lateral genicular artery. Its size varies inversely with
and may necessitate surgical correction; other variations, while asymp- that of the descending genicular artery. The superior lateral genicular
tomatic, may influence technical considerations during vascular surgical artery passes under the tendon of biceps femoris, pierces the lateral
procedures. intermuscular septum and divides into superficial and deep branches.
Anatomical variations of the femoral, profunda femoris, anterior The superficial branch supplies vastus lateralis and anastomoses with
and posterior tibial and fibular arteries have been described elsewhere the descending branch of the lateral circumflex femoral and inferior
in this Section. lateral genicular arteries, while the deep branch anastomoses with the
superior medial genicular artery, forming an anterior arch across the
Popliteal artery femur with the descending genicular artery. The superficial branch is
vulnerable if the lateral patellar retinaculum is divided surgically.
The popliteal artery is the continuation of the femoral artery and crosses Middle genicular artery The middle genicular artery is small. It
the popliteal fossa (see Figs 82.2, 82.4). It descends laterally from the
arises from the popliteal artery near the midpoint of the posterior aspect
opening in adductor magnus to the femoral intercondylar fossa, inclin-
of the knee joint. It pierces the oblique popliteal ligament to supply the
ing obliquely to the distal border of popliteus, where it divides into the
cruciate ligaments and synovial membrane.
anterior and posterior tibial arteries. This division usually occurs at


the proximal end of the interosseous space between the wide tibial
Inferior genicular arteries The inferior medial and lateral genicu-
metaphysis and the slender fibular metaphysis. The artery is relatively
lar arteries arise from the popliteal artery deep to gastrocnemius. The
tethered at the adductor hiatus and again distally by the fascia related
inferior medial genicular artery is deep to the medial head of gastroc-
to soleus, and is therefore susceptible to damage following knee
nemius. It descends along the proximal margin of popliteus, which it
injuries, e.g. dislocation. Aneurysms of the popliteal artery are not
supplies; passes inferior to the medial tibial condyle, under the tibial
uncommon.
collateral ligament; and then ascends anteromedial to the knee joint at
the anterior border of the tibial collateral ligament. It supplies the joint
Variations in the popliteal artery
and the tibia, and anastomoses with the inferior lateral and superior
The popliteal artery may occasionally bifurcate more superiorly and
medial genicular arteries and with the anterior tibial recurrent artery
divide into its terminal branches proximal to popliteus, or it may tri-
and saphenous branch of the descending genicular artery. The inferior
furcate into anterior and posterior tibial and fibular arteries. Either the
lateral genicular artery runs laterally across popliteus and forwards over
anterior tibial or the posterior tibial artery may be reduced or increased
the head of the fibula to the front of the knee joint, passing under the
in size. The size of the fibular artery is usually inversely related to the
lateral head of gastrocnemius, the fibular collateral ligament and the
size of the anterior and posterior tibial arteries. Rarely, the anterior tibial
tendon of biceps femoris. Its branches anastomose with the inferior
artery is the source of the fibular artery, a variation that is almost always
medial and superior lateral genicular arteries; anterior and posterior
associated with a high bifurcation of the popliteal artery.
tibial recurrent arteries; and the circumflex fibular branch of the pos-
The popliteal and inferior gluteal arteries may be joined by a large
terior tibial artery.


anastomotic vessel; in such cases, the femoral artery is hypoplastic
(Kawashima and Sasaki 2010). When this occurs, the popliteal artery Cutaneous branches: the superficial sural arteries The
usually has an abnormal relationship to popliteus, running deep to the
superficial sural arteries are three vessels that leave the popliteal artery,
muscle before dividing into its terminal branches. The popliteal artery
or its side branches, descend between the heads of gastrocnemius and
may pass medially beneath the medial head of gastrocnemius, or may
perforate the deep fascia to supply the skin on the back of the leg. The
pass beneath an aberrant band of muscle in the popliteal fossa; in either
central or median vessel is usually larger than the medial or lateral
case, contraction of the muscles may occlude the artery – a condition
vessels, and usually accompanies the sural nerve.
that may present with claudication on exertion. The popliteal vein is
Fasciocutaneous free and pedicled flaps may be raised on the super-
usually superficial and adjacent to the artery, but it may run deep to the
ficial sural arteries.
artery, or be separated from it by a slip of muscle derived from the
medial head of gastrocnemius.
Superior muscular branches The superior muscular branches are
two or three vessels that arise proximally and pass to adductor magnus
Relations
and the posterior thigh muscles. They anastomose with the termination
Anteriorly, from proximal to distal, are fat covering the femoral pop- of the profunda femoris artery.
liteal surface, the capsule of the knee joint, and the fascia of popliteus.
Posteriorly are semimembranosus (proximally) and gastrocnemius and Sural arteries The two sural arteries are large and arise behind the
plantaris (distally). In between, the artery is separated from the skin knee joint to supply gastrocnemius, soleus and plantaris. They are used
and fasciae by fat and crossed from its lateral to its medial side by the in gastrocnemius musculocutaneous flaps.
tibial nerve and popliteal vein; the vein lies between the nerve and


artery and is adherent to the latter. Laterally are biceps femoris, the tibial
VEINS
nerve, popliteal vein and lateral femoral condyle (all proximal), and
plantaris and the lateral head of gastrocnemius (distal). Medially are
semimembranosus and the medial femoral condyle (proximal), and the The veins draining the knee correspond in name to the arteries and run
tibial nerve, popliteal vein and medial head of gastrocnemius (distally). with them; the named smaller veins drain into the popliteal and
The relations of the popliteal nodes are described below. femoral veins.
Branches (other than terminal) Popliteal vein
Genicular anastomosis There is an intricate arterial anastomosis
around the patella and femoral and tibial condyles (see Fig. 82.1). A The popliteal vein ascends through the popliteal fossa to the opening
superficial network spreads between the fascia and skin around the in adductor magnus, where it becomes the femoral vein (see Figs 78.8,
patella and in the fat deep to the patellar ligament. A deep network lies 78.9B, 80.30). Its relationship to the popliteal artery changes as the vein
on the femur and tibia near their adjoining articular surfaces, and sup- ascends: distally, it is medial to the artery; between the heads of gas-
plies the bone, articular capsule and synovial membrane. The vessels trocnemius, it is superficial (posterior) to the artery; and proximal to
involved in this anastomosis are superior medial and lateral genicular; the knee joint, it is posterolateral to the artery. Its tributaries are the
inferior medial and lateral genicular; descending genicular; descending short saphenous vein; veins corresponding to branches of the popliteal
branch of the lateral circumflex femoral; circumflex fibular; and anterior artery; and muscular veins, including a large branch from each head of
and posterior tibial recurrent arteries. gastrocnemius. There are usually four or five valves in the popliteal vein.
Superior genicular arteries The superior genicular arteries branch Long saphenous vein


from the popliteal artery, curving round proximal to both femoral
condyles to reach the anterior aspect of the knee. The superior medial The course of the long saphenous vein is described on pages
genicular artery lies under semimembranosus and semitendinosus, 1370–1371.


1399
28
ReTPAHC
Key references
Short saphenous vein arteries. The remainder flank the popliteal vessels, receiving trunks that
accompany the anterior and posterior tibial vessels. Popliteal lymphatic
vessels ascend close to the femoral vessels to reach the deep inguinal
The short saphenous vein (small saphenous vein) begins posterior to
nodes; some may accompany the long saphenous vein to the superficial
the lateral malleolus as a continuation of the lateral marginal vein (see
inguinal nodes.
Fig. 78.9B). In the lower third of the calf, it ascends lateral to the cal-
caneal tendon, lying on the deep fascia and covered only by subcutan-
eous tissue and skin. Inclining medially to reach the midline of the calf,
INNERVATION
it penetrates the deep fascia, within which it ascends on gastrocnemius,
only emerging between the deep fascia and gastrocnemius gradually at
about the junction of the middle and proximal thirds of the calf (usually The knee joint is innervated by branches from the obturator, femoral,
well below the lower limit of the popliteal fossa). Continuing its ascent, tibial and common fibular nerves (see Fig. 78.11) (Freeman and Wyke
it passes between the heads of gastrocnemius and proceeds to its termi- 1967). The articular branch of the obturator nerve is the terminal
nation in the popliteal vein, 3–7.5 cm above the knee joint. branch of its posterior division. Muscular branches of the femoral nerve,
especially to vastus medialis, supply articular branches to the knee joint.
Tributaries Genicular branches from the tibial and common fibular nerves accom-
The short saphenous vein connects with deep veins on the dorsum of pany the genicular arteries, and those from the tibial nerve travel with
the foot, receives many cutaneous tributaries in the leg, and sends the medial and middle genicular arteries, while those from the common
several communicating branches proximally and medially to join the fibular nerve travel with the lateral genicular and anterior tibial recur-
long saphenous vein. Sometimes a communicating branch ascends rent arteries.


medially to the accessory saphenous vein: this may be the main con- The femoral and obturator nerves are described on page 1372,
tinuation of the short saphenous vein. In the leg, the short saphenous and the tibial and common fibular nerves are described on
vein lies near the sural nerve and contains 7–13 valves, with one near page 1415.
its termination. Its mode of termination is variable: it may join the long
saphenous vein in the proximal thigh or it may bifurcate, one branch Saphenous nerve
joining the long saphenous vein and the other joining the popliteal or
deep posterior femoral veins. Sometimes it drains distal to the knee in The saphenous nerve is the largest and longest cutaneous branch of the
the long saphenous or sural veins. femoral nerve and the longest nerve in the body (see Figs 78.11, 80.32).
It descends lateral to the femoral artery in the femoral triangle and
enters the adductor canal, where it crosses anterior to the artery to lie
LYMPHATIC DRAINAGE
medial to it. At the distal end of the canal, it leaves the artery and
emerges through the aponeurotic covering with the saphenous branch
Lymphatic drainage is to the popliteal nodes (see Fig. 78.10). Most of
of the descending genicular artery. As it leaves the adductor canal, it
the lymph vessels accompany the genicular arteries; some vessels from
gives off an infrapatellar branch that contributes to the peripatellar
the joint drain directly into a node between the popliteal artery and the
plexus and then pierces the fascia lata between the tendons of sartorius
posterior capsule of the knee joint.
and gracilis, becoming subcutaneous to supply the skin anterior to the
patella. It descends along the medial border of the tibia with the long
Popliteal nodes
saphenous vein and divides distally into a branch that continues along
the tibia to the ankle and a branch that passes anterior to the ankle to
There are usually six small lymph nodes embedded in the fat of the supply the skin on the medial side of the foot, often as far as the first


popliteal fossa. One, near the termination of the short saphenous vein, metatarsophalangeal joint. The saphenous nerve connects with the
drains the superficial region served by this vessel. Another lies between medial branch of the superficial fibular nerve. Near the mid-thigh, it
the popliteal artery and the posterior aspect of the knee, receiving direct provides a branch to the subsartorial plexus. The nerve may become
vessels from the knee joint and those accompanying the genicular entrapped as it leaves the adductor canal.
KEY REFERENCES
Amis AA, Dawkins GP 1991 Functional anatomy of the anterior cruciate A review of the morphological aspects of the bony knee that allow it to be
ligament. Fibre bundle actions related to ligament replacements and an efficient locking mechanism.
injuries. J Bone Joint Surg 73B:260–7.
Scapinelli R 1968 Studies on the vasculature of the human knee joint. Acta
A study of three functional components of the anterior cruciate ligament.
Anat 70:305–31.
Fibre length changes suggested that the ‘isometric point’ aimed at by some
A primary source of detail, complementing the work of Crock on the
ligament replacements lay anterior and superior to the femoral origin of the
vasculature of the bones of the lower limb.
intermediate fibre bundle and towards the roof of the intercondylar notch.
Seebacher JR, Inglis AE, Marshall JL et al 1982 The structure of the postero-
Freeman MAR, Wyke B 1967 The innervation of the knee joint: an anatomi-
lateral aspect of the knee. J Bone Joint Surg 64A:536–41.
cal and histological study in the cat. J Anat 101:505–32.
A work that established the current interpretation of the anatomy of the soft
A classic paper that investigates the gross anatomy and histology of the
tissues of the knee.
articular innervation of the knee joint. Four articular nerve endings were
classified. Tubbs RS, Michelson J, Loukas M et al 2008 The transverse genicular liga-
ment: anatomical study and review of the literature. Surg Radiol Anat
Girgis FG, Marshall JL, Al Monajem ARS 1975 The cruciate ligaments of the
30:5–9.


knee joint. Clin Orthop 106:216–31.
A cadaveric study that identified the transverse ligament of the knee in 55%
A cadaveric study that described the anterior cruciate ligament as having an
of specimens, with two specimens exhibiting a duplicated ligament.
anteromedial and posterolateral band. It suggested that the anteromedial
band was responsible for the anteroposterior drawer sign with flexion. Warren LF, Marshall JL 1979 The supporting structures and layers on the
medial side of the knee: an anatomical analysis. J Bone Joint Surg
Joseph J 1960 Man’s Posture: Electromyographic Studies. Springfield, IL:
61A:56–62.
Thomas.
A cadaveric study of the medial knee that established a three-layer pattern
Electromyography results of the muscles acting on the hip, knee and ankle
for the regional ligaments. joints, and their involvement in maintaining an upright posture.
Rajendran K 1985 Mechanism of locking at the knee joint. J Anat 143:
189–94.


28
ReTPAHC
Knee
REFERENCES
Amis AA, Dawkins GP 1991 Functional anatomy of the anterior cruciate Joseph J 1960 Man’s Posture: Electromyographic Studies. Springfield, IL:
ligament. Fibre bundle actions related to ligament replacements and Thomas.
injuries. J Bone Joint Surg 73B:260–7. Electromyography results of the muscles acting on the hip, knee and ankle
A study of three functional components of the anterior cruciate ligament. joints, and their involvement in maintaining an upright posture.
Fibre length changes suggested that the ‘isometric point’ aimed at by some
Kawashima T, Sasaki H 2010 Reasonable classical concepts in human lower
ligament replacements lay anterior and superior to the femoral origin
limb anatomy from the viewpoint of the primitive persistent sciatic
of the intermediate fibre bundle and towards the roof of the intercondylar
artery and twisting human lower limb. Okajimas Folia Anat Jpn
notch.
87:141–9.
Amis AA, Farahmand F 1996 Biomechanics masterclass: extensor mecha- Newell RLM 1991 A complete intra-articular fat pad around the human
nism of the knee. Curr Orthop 10:102–9. patella. J Anat 179:232.
Claes S, Vereecke E, Maes M et al 2013 Anatomy of the anterolateral ligament Nissman DB, Hobbs RH, Pope TL et al 2008 Imaging the knee: ligaments.
of the knee. J Anat 223:321–8. Appl Radiol 37:25–32.
Cormack GC, Lamberty BGH 1994 The Arterial Anatomy of Skin Flaps. Omololu B, Tella A, Ogunlade SO et al 2003 Normal values of knee angle,
Edinburgh: Elsevier, Churchill Livingstone. intercondylar and intermalleolar distances in Nigerian children. West
Crock HV 1967 The Blood Supply of the Lower Limb Bones in Man. London: Afr J Med 22:301–4.
Livingstone. Rajendran K 1985 Mechanism of locking at the knee joint. J Anat 143:


Falciglia F, Guzzanti V, Di Ciommo V et al 2009 Physiological knee laxity 189–94.
during pubertal growth. Bull NYU Hosp Jt Dis 67:325–9. A review of the morphological aspects of the bony knee that allow it to be
Freeman MAR, Wyke B 1967 The innervation of the knee joint: an anatomi- an efficient locking mechanism.
cal and histological study in the cat. J Anat 101:505–32. Scapinelli R 1968 Studies on the vasculature of the human knee joint. Acta
A classic paper that investigates the gross anatomy and histology of the Anat 70:305–31.
articular innervation of the knee joint. Four articular nerve endings were A primary source of detail, complementing the work of Crock on the
classified. vasculature of the bones of the lower limb.
Ghadially FN, Lalonde JM, Wedge JH 1983 Ultrastructure of normal and Seebacher JR, Inglis AE, Marshall JL et al 1982 The structure of the postero-
torn menisci of the human knee joint. J Anat 136:773–91. lateral aspect of the knee. J Bone Joint Surg 64A:536–41.
Girgis FG, Marshall JL, Al Monajem ARS 1975 The cruciate ligaments of the A work that established the current interpretation of the anatomy of the soft
knee joint. Clin Orthop 106:216–31. tissues of the knee.
A cadaveric study that described the anterior cruciate ligament as having an
Tennant TD, Birch NC, Holmes MJ et al 1998 Knee pain and the infrapatellar
anteromedial and posterolateral band. It suggested that the anteromedial
branch of the saphenous nerve. J Roy Soc Med 91:573–5.
band was responsible for the anteroposterior drawer sign with flexion.
Tubbs RS, Michelson J, Loukas M et al 2008 The transverse genicular liga-
Gronblad M, Korkala O, Leisi P et al 1985 Innervation of synovial mem- ment: anatomical study and review of the literature. Surg Radiol Anat


brane and meniscus. Acta Orthop Scand 56:484–6. 30:5–9.
Gupte CM, Bull AMJ, Thomas RD et al 2003 A review of the function A cadaveric study that identified the transverse ligament of the knee in 55%
and biomechanics of the meniscofemoral ligaments. Arthroscopy 19: of specimens, with two specimens exhibiting a duplicated ligament.
161–71.
Warren LF, Marshall JL 1979 The supporting structures and layers on the
Hamel A, Ploteau S, Lancien M et al 2012 Arterial supply to the tibial tuber- medial side of the knee: an anatomical analysis. J Bone Joint Surg 61A:
osity: involvement in patellar ligament transfer in children. Surg Radiol 56–62.
Anat 34:311–16. A cadaveric study of the medial knee that established a three-layer pattern
Jones G, Ding C, Glisson M et al 2003 Knee articular cartilage development for the regional ligaments.
in children: a longitudinal study of the effect of sex, growth, body com-
Watanabe M, Takeda S, Ikeuchi H 1979 Atlas of Arthroscopy. Berlin: Springer.
position, and physical activity. Pediatr Res 54:230–6.
1399.e1


CHAPTER
83
Leg
This chapter describes the shafts of the tibia and fibula, the soft tissues soleal ridge of the tibia and to the fibula, inferomedial to the fibular
that surround them and the interosseous membrane between them. The attachment of soleus. Between these bony attachments, it is continuous
superior (proximal) and inferior (distal) tibiofibular joints are described with the fascia covering popliteus, which is, in effect, an expansion from
on pages 1385 and 1433, respectively. the tendon of semimembranosus. At intermediate levels it is thin but
distally, where it covers the tendons behind the malleoli, it is thick and
continuous with the flexor and superior fibular retinacula.
SKIN AND SOFT TISSUES
Interosseous membrane
SKIN The interosseous membrane connects the interosseous borders of the
tibia and fibula (Fig. 83.1). It is interposed between the anterior and
Vascular supply and lymphatic drainage
Posterior ligament of
The cutaneous arterial supply is derived from branches of the popliteal, fibular head
anterior tibial, posterior tibial and fibular vessels (see Fig. 78.5). Mul
tiple fasciocutaneous perforating branches from each vessel pass along Head of fibula
intermuscular septa to reach the skin; musculocutaneous perforators
traverse muscles before reaching the skin. In some areas, there is an
Ligament of Barkow
additional, direct cutaneous supply from vessels that accompany cuta
neous nerves, e.g. the descending genicular artery (saphenous artery) Opening for anterior
and superficial sural arteries. Fasciocutaneous and direct cutaneous art tibial vessels
erial branches have a longitudinal orientation in the skin, whereas the
musculocutaneous branches are more radially oriented. For further
details, consult Cormack and Lamberty (1994).
Cutaneous veins are tributaries of vessels that correspond to the
named arteries. Cutaneous lymphatic vessels running on the medial
side of the leg accompany the long saphenous vein and drain to the
superficial inguinal nodes, while those from the lateral and posterior
sides of the leg accompany the short saphenous vein and pierce the


deep fascia to drain into the popliteal nodes.
Interosseous membrane
Innervation
(syndesmosis)
The skin of the leg is supplied by branches of the saphenous, posterior
femoral cutaneous, common fibular and tibial nerves (see below and
Figs 78.11, 78.12, 78.17, 78.18).
SOFT TISSUES
Deep fascia
The deep fascia of the leg is continuous with the fascia lata and is
attached around the knee to the patellar margin, the patellar ligament,
the tuberosity and condyles of the tibia, and the head of the fibula.
Posteriorly, where it covers the popliteal fossa as the popliteal fascia,
it is strengthened by transverse fibres and is perforated by the short
saphenous vein and sural nerve. It receives lateral expansions from the
tendon of biceps femoris and multiple medial expansions from the
tendons of sartorius, gracilis, semitendinosus and semimembranosus.
The deep fascia blends with the periosteum on the subcutaneous surface
of the tibia and the subcutaneous surfaces of the fibular head and lateral Opening for perforating
branch of fibular artery
malleolus, and is continuous below with the extensor and flexor reti
nacula. It is thick and dense in the proximal and anterior part of the
leg, where fibres of tibialis anterior and extensor digitorum longus are
attached to its deep surface, and is thinner posteriorly, where it covers
gastrocnemius and soleus. On the lateral side, it is continuous with the
anterior and posterior intermuscular septa of the leg, which are attached
to the anterior and posterior borders of the fibula, respectively. Groove for tendon
of tibialis posterior
Transverse intermuscular septum
The transverse intermuscular septum of the leg is a fibrous stratum
between the superficial and deep muscles of the calf. It extends trans Inferior transverse ligament
versely from the medial margin of the tibia to the posterior border of Fig. 83.1 The posterior aspect of the interosseous membrane. Note the
1400 the fibula. Proximally, where it is thick and dense, it is attached to the contrasting direction of the fibre bundles around the vascular openings.


Bones
1401
38
RETPAHC
A Tibialis anterior B
Tibialis posterior
Tibia
Extensor digitorum longus
Popliteus, lowest part
Anterior tibial artery
Fibularis longus
Flexor digitorum longus
Posterior tibial artery Deep fibular nerve
and tibial nerve Superficial fibular nerve
Long saphenous vein
Fibula
Fibular artery
Flexor hallucis longus
Gastrocnemius,
medial head Gastrocnemius,
lateral head
Cutaneous vein
Soleus
Sural communicating branch
Plantaris
Sural nerve Short saphenous vein
Fig. 83.2 A, A transverse (axial) section through the left leg, approximately 10 cm distal to the knee joint. B, Colour-coded axial magnetic resonance
imaging (MRI) of the leg. Observe the anterior (blue), lateral (red) and posterior (deep part yellow and superficial part green) compartments of the leg.
(C, continued online)
posterior groups of crural muscles; some members of each group are with an additional contribution from the fibular artery to extensor hal
attached to the corresponding surface of the interosseous membrane. lucis longus. The muscles of the posterior compartment are supplied by
The anterior tibial artery passes forwards through a large oval opening the popliteal, posterior tibial and fibular arteries. The muscles of the
near the proximal end of the membrane, and the perforating branch of lateral compartment are supplied by the anterior tibial and fibular arter
the fibular artery pierces it distally. An associated ligament (ligament of ies, and to a lesser extent proximally, by a branch from the popliteal
Barkow), in the same plane as the interosseous membrane, may be artery.
found uniting the proximal tibiofibular joint; when present, it forms
the upper half of this oval opening (see Fig. 83.1) (Tubbs et al 2009). Trauma and soft tissues of the leg
Its fibres are predominantly oblique and most descend laterally; those The relative paucity of soft tissue in the shin region and the subcutan
that descend medially include a bundle at the proximal border of the eous position of the medial surface of the tibia means that even trivial


proximal opening. The thickness of the interosseous membrane differs soft tissue injury may lead to serious problems such as ulceration and
between its thin centre and thick tibial and fibular borders. The mem osteomyelitis. In the elderly, these soft tissues are often especially thin
brane is continuous distally with the interosseous ligament of the distal and unhealthy, reflecting the effects of ageing and venous stasis (see
tibiofibular joint. below). Tibial fractures are common in the young and, partly as a result
of poor soft tissue coverage, they are often open injuries. Diminished
Retinacula
blood supply to the bone, caused by traumatic stripping of attached
The retinacula at the ankle joint are described on page 1418.
soft tissues, and the risk of contamination add greatly to the risk of
Osteofascial compartments nonunion and infection of the fracture. Healing of fractures at the
junction of the middle and lower thirds of the tibia is compromised by
The compartments of the leg are particularly well defined and are the
the relatively poor blood supply to this region. Injury to the leg may
most common sites at which osteofascial compartment syndromes
result in elevated pressures of one or more compartments (socalled
occur. The three main compartments are anterior (extensor), lateral
compartment syndrome); this clinical scenario is manifested by the ‘six
(fibular) and posterior (flexor). The posterior compartment is divided
Ps’: pain, paraesthesias, pallor, paralysis, pulselessness and poikilother
into deep and superficial parts by the transverse intermuscular septum
mia (differing temperatures in the affected and unaffected limbs).
(Fig. 83.2). These compartments are enclosed by the unyielding deep
fascia and separated from each other by the bones of the leg and inter
osseous membrane, and by the anterior and posterior intermuscular
BONES
septa that pass from the deep fascia to the fibula. The anterior compart
ment, the least expansile of the three, is bounded by the deep fascia,
the interosseous surfaces of the tibia and fibula, the interosseous mem TIBIA
brane and the anterior intermuscular septum. The lateral compartment


lies between the anterior and posterior intermuscular septa, and is The tibia lies medial to the fibula and is exceeded in length only by the
bordered laterally by the deep fascia and medially by the lateral surface femur (Figs 83.3–83.4). The tibial shaft is triangular in section and has
of the fibula. The posterior compartment is bounded by the deep fascia, expanded ends; a strong medial malleolus projects distally from the
the posterior intermuscular septum, the fibula and tibia, and the inter smaller distal end. The anterior border of the shaft is sharp and curves
osseous membrane. Its relatively expansile superficial component is medially towards the medial malleolus. Together with the medial and
separated from the compacted deep component by the transverse inter lateral borders, it defines the three surfaces of the bone. The exact shape
muscular septum, reinforced by the deep aponeurosis of soleus. Knowl and orientation of these surfaces show individual and racial variations.
edge of the compartmental anatomy of the leg is important in planning In children, the mean tibial length is greater in males than in females
the treatment of compartment syndromes and for soft tissue tumour (Oeffinger et al 2010).
resections of the leg.
The nerve supply of the muscles in the compartments follows the Proximal end
‘one compartment – one nerve’ principle: the deep fibular nerve sup The expanded proximal end bears the weight transmitted through the
plies the anterior compartment, the superficial fibular nerve supplies femur. It consists of medial and lateral condyles, an intercondylar area
the lateral compartment, and the tibial nerve supplies the posterior and the tibial tuberosity.
compartment. Magnetic resonance imaging (MRI) is the best imaging
modality for evaluating the soft tissues of the leg. Most of the muscle Condyles The tibial condyles overhang the proximal part of the pos
in the anterior compartment is supplied by the anterior tibial artery, terior surface of the shaft. Both condyles have articular facets on their


38
RETPAHC
Leg
C
Fig. 83.2 C, An axial T2-weighted MRI of the leg in a patient with anterior
compartment denervation (arrow).
1401.e1


LEg
1402
9
NOITCES
A B Fig. 83.3 A, The left tibia and fibula, anterior
aspect. Key: 1, medial condyle; 2, tibial tuberosity;
10
1 7 3, anterior border of tibia; 4, interosseous border
1 11 of tibia; 5, medial surface; 6, medial malleolus; 7,
8 2 Gerdy’s tubercle; 8, lateral condyle; 9, head of
12
2 3 13 fibula; 10, interosseous border of fibula; 11,
9 4 anterior border of fibula; 12, medial crest; 13,
14 anterior surface; 14, subcutaneous area; 15, lateral
15 malleolus. B, The muscle attachments. Key: 1,
semimembranosus; 2, medial patellar retinaculum;
5 3, epiphysial line (growth plate); 4, tibial collateral
6 16 ligament; 5, gracilis; 6, sartorius; 7,
7 17 semitendinosus; 8, tibialis anterior; 9, capsular
attachment; 10, iliotibial tract; 11, capsular
18 attachment; 12, fibular collateral ligament; 13,
8 biceps femoris; 14, patellar ligament; 15,
epiphysial line (growth plate); 16, fibularis longus;
17, extensor digitorum longus; 18, tibialis
3 posterior; 19, fibularis brevis; 20, extensor hallucis
longus; 21, extensor digitorum longus; 22, fibularis
19
tertius; 23, epiphysial line (growth plate); 24,
epiphysial line (growth plate).
10
4
20
11
21
12
13
5
22
14 23
9
24
6
15
superior surfaces, separated by an irregular, nonarticular intercondylar edge is a sharp ridge between the lateral condyle and lateral surface of


area. The condyles are visible and palpable at the sides of the patellar the shaft. The condyles, their articular surfaces and the intercondylar
ligament, the lateral being more prominent. In the passively flexed area are described on pages 1386–1387.
knee, the anterior margins of the condyles are palpable in depressions
that flank the patellar ligament. Tibial tuberosity The tibial tuberosity is the truncated apex of a
The fibular articular facet on the posteroinferior aspect of the lateral triangular area where the anterior condylar surfaces merge. It projects
condyle faces distally and posterolaterally. The angle of inclination of only a little, and is divided into distal rough and proximal smooth
the superior tibiofibular joint varies between individuals, and may be regions. The distal region is palpable and is separated from skin by the
horizontal or oblique. Superomedial to it, the condyle is grooved on subcutaneous infrapatellar bursa. A line across the tibial tuberosity
its posterolateral aspect by the tendon of popliteus; a synovial recess marks the distal limit of the proximal tibial growth plate (see Fig. 83.3).
intervenes between the tendon and bone. The anterolateral aspect of The patellar ligament is attached to the smooth bone proximal to this,
the condyle is separated from the lateral surface of the shaft by a sharp its superficial fibres reaching a rough area distal to the line. The deep
margin for the attachment of deep fascia. The distal attachment of the infrapatellar bursa and fibroadipose tissue intervene between the bone
iliotibial tract makes a flat and usually definite marking (Gerdy’s tuber and tendon proximal to its site of attachment. The latter may be marked
cle) on its anterior aspect. This tubercle, which is triangular and facet distally by a somewhat oblique ridge, on to which the lateral fibres of
like, is usually palpable through the skin. the patellar ligament are inserted more distally than the medial fibres.
The anterior condylar surfaces are continuous with a large triangular This knowledge is necessary for avoiding damage to this structure when
area whose apex is distal and formed by the tibial tuberosity. The lateral performing an osteotomy just above the tibial tuberosity in a lateral to


Bones
1403
38
RETPAHC
A 10 B Fig. 83.4 A, The left tibia and fibula, posterior
6
1 aspect. Key: 1, groove for tendon of popliteus;
1 2, apex of head of fibula; 3, head of fibula; 4, neck
2 11 of fibula; 5, medial crest; 6, interosseous border of
7 tibia; 7, posterior border; 8, groove for fibular
3 tendons; 9, lateral malleolus; 10, intercondylar
8 eminence; 11, groove for semimembranosus
4
attachment; 12, soleal line; 13, nutrient foramen;
14, vertical line; 15, medial border of tibia; 16,
9
medial malleolus; 17, groove for tibialis posterior
2 tendon. B, The muscle attachments. Key: 1, gap
in capsule for popliteus tendon; 2, soleus; 3, flexor
10
12 hallucis longus; 4, fibularis brevis; 5, epiphysial
line (growth plate); 6, capsular attachment; 7,
semimembranosus; 8, epiphysial lines (growth
plates); 9, popliteus; 10, soleus; 11, tibialis
posterior; 12, flexor digitorum longus; 13,
13 epiphysial line (growth plate); 14, capsular
attachment.
5 3
11
14
12
15
6
7
4
13
16 5
8
17 14
9
medial direction. In habitual squatters, a vertical groove on the anterior The anteromedial surface, between the anterior and medial borders,
surface of the lateral condyle is occupied by the lateral edge of the is broad, smooth and almost entirely subcutaneous. The lateral surface,
patellar ligament in full flexion of the knee. between the anterior and interosseous borders, is also broad and
smooth. It faces laterally in its proximal threequarters and is trans
Shaft versely concave. Its distal quarter bends to face anterolaterally, on


The shaft is triangular in section and has (antero)medial, lateral and account of the medial deviation of the anterior and distal interosseous
posterior surfaces separated by anterior, lateral (interosseous) and borders. This part of the surface is somewhat convex. The posterior
medial borders. It is narrowest at the junction of the middle and distal surface, between the interosseous and medial borders, is widest above,
thirds, and expands gradually towards both ends. The anterior border where it is crossed distally and medially by an oblique, rough soleal
descends from the tuberosity to the anterior margin of the medial line. A faint vertical line descends from the centre of the soleal line for
malleolus and is subcutaneous throughout. Except in its distal quarter, a short distance before becoming indistinct. A large vascular groove
where it is indistinct, it is a sharp crest. It is slightly sinuous, and turns adjoins the end of the line and descends distally into a nutrient foramen.
medially in the distal quarter. The interosseous border begins distal and Deep fascia and, proximal to the medial malleolus, the medial end of
anterior to the fibular articular facet and descends to the anterior border the superior extensor retinaculum are attached to the anterior border.
of the fibular notch; it is indistinct proximally. The interosseous mem Posterior fibres of the tibial collateral ligament and slips of semimem
brane is attached to most of its length, connecting the tibia to the fibula. branosus and the popliteal fascia are attached to the medial border
The medial border descends from the anterior end of the groove on the proximal to the soleal line, and some fibres of soleus and the fascia
medial condyle to the posterior margin of the medial malleolus. Its covering the deep calf muscles are attached distal to the line. The distal
proximal and distal quarters are ill defined but its central region is sharp medial border runs into the medial lip of a groove for the tendon of
and distinct. tibialis posterior. The interosseous membrane is attached to the lateral


LEg
1404
9
NOITCES
border, except at either end of this border. It is indistinct proximally Muscle attachments
where a large gap in the membrane transmits the anterior tibial vessels. The patellar ligament is attached to the proximal half of the tibial
Distally, the border is continuous with the anterior margin of the fibular tuberosity. Semimembranosus is attached to the distal edge of the
notch, to which the anterior tibiofibular ligament is attached. groove on the posterior surface of the medial condyle; a tubercle at the
The anterior part of the tibial collateral ligament is attached to an lateral end of the groove is the main attachment of the tendon of this
area approximately 5 cm long and 1 cm wide near the medial border muscle. Slips from the tendon of biceps femoris are attached to the
of the proximal medial surface. The remaining medial surface is subcu lateral tibial condyle anteroproximal to the fibular articular facet (see
taneous and crossed obliquely by the long saphenous vein. Tibialis Fig. 83.3B). Proximal fibres of extensor digitorum longus and (occa
anterior is attached to the proximal twothirds of the lateral surface. The sionally) fibularis longus are attached distal to this area. Slips of semi
distal third, devoid of attachments, is crossed in mediolateral order by membranosus are attached to the medial border of the shaft posteriorly,
the tendons of tibialis anterior (lying just lateral to the anterior border), proximal to the soleal line. Some fibres of soleus attach to the postero
extensor hallucis longus, the anterior tibial vessels and deep fibular medial surface distal to the line. Semimembranosus is attached to the
nerve, extensor digitorum longus and fibularis tertius. medial surface proximally, near the medial border, behind the attach
On the posterior surface, popliteus is attached to a triangular area ment of the anterior part of the tibial collateral ligament. Anterior to
proximal to the soleal line, except near the fibular articular facet. The this area (in anteroposterior sequence) are the linear attachments of


popliteal aponeurosis, soleus and its fascia, and the transverse inter the tendons of sartorius, gracilis and semitendinosus; these rarely mark
muscular septum are all attached to the soleal line; the proximal end the bone. Tibialis anterior is attached to the proximal twothirds of the
of the line does not reach the interosseous border, and is marked by a lateral (extensor) surface. Popliteus is attached to the posterior surface
tubercle for the medial end of the tendinous arch of soleus. Lateral to in a triangular area proximal to the soleal line, except near the fibular
the tubercle, the posterior tibial vessels and tibial nerve descend on articular facet (see Fig. 83.4B). Soleus and its associated fascia are
tibialis posterior. Distal to the soleal line, a vertical line separates the attached to the soleal line itself. Flexor digitorum longus and tibialis
attachments of flexor digitorum longus and tibialis posterior. Nothing posterior are attached to the posterior surface distal to the soleal line,
is attached to the distal quarter of this surface, but the area is crossed medial and lateral, respectively, to the vertical line (see above).
medially by the tendon of tibialis posterior travelling to a groove on
the posterior aspect of the medial malleolus. Flexor digitorum longus Vascular supply
crosses obliquely behind tibialis posterior; the posterior tibial vessels The proximal end of the tibia is supplied by metaphysial arteries from
and nerve and flexor hallucis longus contact only the lateral part of the the genicular anastomosis. The nutrient foramen usually lies near the
distal posterior surface. soleal line and transmits a branch of the posterior tibial artery; the
nutrient vessel may also arise at the level of the popliteal bifurcation or
Distal end
as a branch from the anterior tibial artery. On entering the bone, the
The slightly expanded distal end of the tibia has anterior, medial, pos nutrient artery divides into ascending and descending branches. The
terior, lateral and distal surfaces. It projects inferomedially as the medial periosteal supply to the shaft arises from the anterior tibial artery and


malleolus. The distal end of the tibia, when compared to the proximal from muscular branches. The distal metaphysis is supplied by branches
end, is laterally rotated (tibial torsion). The torsion begins to develop from the arterial anastomosis around the ankle.
in utero and progresses throughout childhood, mainly during the first
four years of life (Kristiansen et al 2001), until skeletal maturity is Innervation
attained. Some of the femoral neck anteversion seen in the newborn The proximal and distal ends of the tibia are innervated by branches
may persist in adult females: this causes the femoral shaft and knee to from the nerves that supply the knee joint and ankle joint, respectively.
be medially rotated, which may lead the tibia to develop a compens The periosteum of the shaft is supplied by branches from the nerves
atory external torsion to counteract the tendency of the feet to turn that innervate the muscles attached to the tibia.
inwards. Tibial torsion is approximately 30° in Caucasian and Asian
populations, but is significantly greater in Africans (Eckhoff et al 1994). Ossification
The smooth anterior surface projects beyond the distal surface, from The tibia ossifies from three centres: one in the shaft and one in each
which it is separated by a narrow groove. The capsule of the ankle joint epiphysis. Ossification (see Figs 83.3–83.4; Fig. 83.5) begins in mid
is attached to an anterior groove near the articular surface. The medial shaft at about the seventh intrauterine week. The proximal epiphysial
surface is smooth and continuous above and below with the medial centre is usually present at birth: at approximately 10 years, a thin
surfaces of the shaft and medial malleolus, respectively; it is subcutan anterior process from the centre descends to form the smooth part of
eous and visible. The posterior surface is smooth except where it is the tibial tuberosity. A separate centre for the tuberosity may appear at
crossed near its medial end by a nearly vertical but slightly oblique about the twelfth year and soon fuses with the epiphysis. Distal strata
groove, which is usually conspicuous and extends to the posterior of the epiphysial plate are composed of dense collagenous tissue in


surface of the malleolus. The groove is adapted to the tendon of tibialis which the fibres are aligned with the patellar ligament. Exaggerated
posterior, which usually separates the tendon of flexor digitorum longus traction stresses may account for Osgood–Schlatter disease, in which
from the bone. More laterally, the posterior tibial vessels, tibial nerve
and flexor hallucis longus contact this surface. The lateral surface is the
Joins shaft sixteenth
triangular fibular notch; its anterior and posterior edges project and
to eighteenth year
converge proximally to the interosseous border. The floor of the notch
is roughened proximally by a substantial interosseous ligament but is
smooth distally and is sometimes covered by articular cartilage. The
anterior and posterior tibiofibular ligaments are attached to the corre
sponding edges of the notch. The distal surface articulates with the talus
and is wider in front, concave sagittally and slightly convex transversely,
i.e. saddleshaped. Medially, it continues into the malleolar articular
surface, which may extend into the groove that separates it from the
anterior surface of the shaft. Such extensions, medial or lateral or both,
are squatting facets, and they articulate with reciprocal talar facets in At birth End of Twelfth Sixteenth to
extreme dorsiflexion. These features have been used in the field of first year year eighteenth year
forensic medicine to identify the race of skeletal material.
Medial malleolus The short, thick medial malleolus has a smooth
lateral surface with a crescentic facet that articulates with the medial
surface of the talus. Its anterior aspect is rough and its posterior aspect
features the continuation of the groove from the posterior surface of
the tibial shaft for the tendon of tibialis posterior. The distal border is
pointed anteriorly, posteriorly depressed, and gives attachment to the
deltoid ligament. The tip of the medial malleolus does not project as
far distally as the tip of the lateral malleolus, the latter also being the
more posteriorly located of the two malleoli. The capsule of the ankle Joins shaft
Unossified (cartilaginous) regions sixteenth to eighteenth year
joint is attached to the anterior surface of the medial malleolus, and


the flexor retinaculum is attached to its prominent posterior border. Fig. 83.5 Stages in the ossification of the tibia (not to scale).


Muscles
1405
38
RETPAHC
fragmentation of the epiphysis of the tibial tuberosity occurs during interosseous ligament. The interosseous membrane attached to this
adolescence and produces a painful swelling around it. Healing occurs border does not reach the fibular head, which leaves a gap through
once the growth plate fuses, leaving a bony protrusion. Prolonged which the anterior tibial vessels pass. The posterior border is proximally
periods of traction with the knee extended, both in children and adol indistinct, and the posterior intermuscular septum is attached to all but
escents, can lead to growth arrest of the anterior part of the proximal its distal end. The medial crest is related to the fibular artery. A layer of
epiphysis, which results in bowing of the proximal tibia as the posterior deep fascia separating the tendon of tibialis posterior from flexor hal
tibia continues to grow. The proximal epiphysis fuses in the sixteenth lucis longus and flexor digitorum longus is attached to the medial crest.
year in females and the eighteenth in males. The distal epiphysial centre
appears early in the first year and joins the shaft at about the fifteenth Lateral malleolus
year in females and the seventeenth in males. The medial malleolus is The distal end of the fibula forms the lateral malleolus, which projects
an extension from the distal epiphysis and starts to ossify in the seventh distally and posteriorly (see Figs 83.3–83.4). Its lateral aspect is subcu
year; it may have its own separate ossification centre. An accessory taneous while its posterior aspect has a broad groove with a prominent
ossification centre sometimes appears at the tip of the medial malleo lateral border. Its anterior aspect is rough, round and continuous with
lus, more often in females than in males. It fuses during the eighth year the tibial inferior border. The medial surface has a triangular articular
in females and the ninth year in males; it should not be confused with facet, vertically convex, its apex distal, which articulates with the lateral
an os subtibiale, which is a rare accessory bone found on the posterior talar surface. Behind this facet is a rough malleolar fossa pitted by vas


aspect of the medial malleolus. The average growth rate of the distal cular foramina. The posterior tibiofibular ligament and, more distally,
tibia decreases from a plateau of about 11 years of age in boys and 10 the posterior talofibular ligament, are attached in the fossa. The ant
years of age in girls (Kärrholm et al 1984). erior talofibular ligament is attached to the anterior surface of the
lateral malleolus; the calcaneofibular ligament is attached to the notch
anterior to its apex. The tendons of fibularis brevis and longus groove
FIBULA its posterior aspect; the latter is superficial and covered by the superior
fibular retinaculum.
The fibula (see Figs 83.3–83.4) is much more slender than the tibia and
Muscle attachments
is not directly involved in transmission of weight. It has a proximal
head, a narrow neck, a long shaft and a distal lateral malleolus. The The main attachments of biceps femoris embrace the fibular collateral
shaft varies in form, being variably moulded by attached muscles; these ligament in front of the apex of the fibular head. Extensor digitorum
variations may be confusing. longus is attached to the head anteriorly, fibularis longus anterolat
erally, and soleus posteriorly. Extensor digitorum longus, extensor hal
Head lucis longus and fibularis tertius are attached to the anteromedial
The head of the fibula is irregular in shape and projects anteriorly, (extensor) surface. Fibularis longus is attached to the whole width of
posteriorly and laterally. A round facet on its proximomedial aspect the lateral (fibular) surface in its proximal third, but in its middle third
articulates with a corresponding facet on the inferolateral surface of the only to its posterior part, behind fibularis brevis. The latter continues
lateral tibial condyle. It faces proximally and anteromedially, and has its attachment almost to the distal end of the shaft.
an inclination that may vary among individuals from almost horizontal Muscle attachments to the posterior surface, which is divided longi


to an angle of up to 45°. A blunt apex projects proximally from the tudinally by the medial crest, are complex. Between the crest and inter
posterolateral aspect of the head and is often palpable approximately osseous border, the posterior surface is concave. Tibialis posterior is
2 cm distal to the knee joint. The fibular collateral ligament is attached attached throughout most (the proximal threequarters) of this area; an
in front of the apex, embraced by the main attachment of biceps intramuscular tendon may ridge the bone obliquely. Soleus is attached
femoris. The tibiofibular joint capsule is attached to the margins of the between the crest and the posterior border on the proximal quarter of
articular facet. The common fibular nerve crosses posterolateral to the the posterior surface; its tendinous arch is attached to the surface proxi
neck and can be rolled against the underlying bone at this location. mally (see Fig. 83.4B). Flexor hallucis longus is attached distal to soleus
on the posterior surface and almost reaches the distal end of the shaft.
Shaft
The shaft has three borders and surfaces, each associated with a particu Vascular supply
lar group of muscles. The anterior border ascends proximally from the A little proximal to the midpoint of the posterior surface (14–19 cm
apex of an elongated triangular area that is continuous with the lateral from the apex), a distally directed nutrient foramen on the fibular shaft
malleolar surface, to the anterior aspect of the fibular head. The poste receives a branch of the fibular artery. An appreciation of the detailed
rior border, continuous with the medial margin of the posterior groove anatomy of the fibular artery in relation to the fibula is fundamental to
on the lateral malleolus, is usually distinct distally but often rounded the raising of osteofasciocutaneous free flaps. Free vascularized diaphys
in its proximal half. The interosseous border is medial to the anterior ial grafts may also be taken on a fibular arterial pedicle. The proximal
border and somewhat posterior. Over the proximal twothirds of the and distal ends receive metaphysial vessels from the arterial anastomo


fibular shaft the two borders approach each other, with the surface ses at the knee and ankle, respectively (Taylor and Razaboni 1994).
between the two being narrowed to 1 mm or less.
The lateral surface, between the anterior and posterior borders and Innervation
associated with the fibular muscles, faces laterally in its proximal three The proximal and distal ends of the bone are supplied by branches of
quarters. The distal quarter spirals posterolaterally to become continu nerves that innervate the knee and superior tibiofibular joint, and the
ous with the posterior groove of the lateral malleolus. The anteromedial ankle and inferior tibiofibular joints, respectively. The periosteum of
(sometimes simply termed anterior, or medial) surface, between the the shaft is supplied by branches from the nerves that innervate the
anterior and interosseous borders, usually faces anteromedially but muscles attached to the fibula.
often directly anteriorly. It is associated with the extensor muscles.
Though wide distally, it narrows in its proximal half and may become Ossification
a mere ridge. The posterior surface, between the interosseous and pos The fibula ossifies from three centres: one each for the shaft and the
terior borders, is the largest and is associated with the flexor muscles. extremities. The process begins in the shaft at about the eighth week in
Its proximal twothirds are divided by a longitudinal medial crest, sepa utero; in the distal end in the first year; and in the proximal end at about
rated from the interosseous border by a grooved surface that is directed the third year in females and the fourth year in males. The distal epi
medially. The remaining surface faces posteriorly in its proximal half; physis unites with the shaft at about the fifteenth year in females and
its distal half curves on to the medial aspect. Distally, this area occupies the seventeenth year in males, whereas the proximal epiphysis does not
the fibular notch of the tibia, which is roughened by the attachment of unite until about the seventeenth year in females and the nineteenth
the principal interosseous tibiofibular ligament. The triangular area year in males. A longitudinal radiographic study of children has shown


proximal to the lateral surface of the lateral malleolus is subcutaneous; that the proximal growth plate of the fibula contributes more to growth
muscles cover the rest of the shaft. than the proximal growth plate of the tibia, their growth contributions
The anterior border is divided distally into two ridges that enclose a being 61% and 57%, respectively (Pritchett and Bortel 1997).
triangular subcutaneous surface. The anterior intermuscular septum is
attached to its proximal threequarters. The lateral end of the superior
MUSCLES
extensor retinaculum is attached distally on the anterior border of the
triangular area and the lateral end of the superior fibular retinaculum
is attached distally on the posterior margin of the triangular area. The The muscles of the leg consist of an anterior group of extensor muscles,
interosseous border ends at the proximal limit of the rough area for the which produce dorsiflexion (extension) of the ankle; a posterior group


38
RETPAHC
Leg
An os subfibulare is an occasional and separate entity and lies pos
terior to the tip of the fibula, whereas the distal fibular apophysis lies
anteriorly. An os retinaculi is rarely encountered; if present, it overlies
the bursa of the distal fibula within the fibular retinaculum. Fibular
dimelia is characterized by duplication of the fibula, tibial aplasia and
partial duplication of the foot with mirror polydactyly, and may be
associated with ulnar dimelia and calcaneal duplication. It has been
postulated that a reestablishment of limb polarity during embryogen
esis may account for this condition (Bayram et al 1996, Ganey et al
2000).
1405.e1


LEg
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9
NOITCES
A B
Patella Biceps femoris
Iliotibial tract Vastus lateralis
Patellar ligament
Iliotibial tract
Tibial tuberosity Patella
Patellar ligament Head of fibula
Gastrocnemius
Fibularis longus Gastrocnemius
Fibularis longus
Tibialis anterior
Soleus
Extensor digitorum longus Tibialis anterior
Soleus
Tibia Fibularis brevis
Extensor digitorum longus
Fibularis brevis
Tibialis anterior
Extensor hallucis longus
Calcaneal tendon
Extensor hallucis longus Inferior extensor retinaculum
Lateral malleolus
Extensor
hallucis brevis
Superior fibular
Medial malleolus retinaculum
Lateral malleolus
Inferior extensor Fibularis
retinaculum longus
Extensor digitorum longus
Extensor Fibularis
hallucis longus brevis
Fibularis tertius
Extensor digitorum longus Fibularis tertius Extensor digitorum brevis
Extensor
hallucis brevis Extensor digitorum brevis
Fig. 83.6 Muscles of the left leg and foot. The fasciae have been
removed. A, Anterior view. B, Lateral view. (With permission from
Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th ed,
Elsevier, Urban & Fischer. Copyright 2013.)
of flexor muscles, which produce plantar flexion (flexion); and a lateral Attachments to the talus, first metatarsal head, base of the proximal
group of muscles, which evert the ankle and which are derived, embryo phalanx of the hallux, and extensor retinaculum have been recorded.
logically, from the anterior muscle group. The greater bulk of the
muscles in the calf is commensurate with the powerful propulsive role Relations Tibialis anterior overlaps the anterior tibial vessels and
of the plantar flexors in walking and running. deep fibular nerve in the upper part of the leg. It lies on the tibia and
interosseous membrane. Extensor digitorum longus and extensor hal