18
RETPAHC
Hip
Fig. 81.1B Anteroposterior radiograph of an
adult male pelvis (the hip joint is normal).
1, ossification in right iliolumbar ligament; 2, pubic
1
symphysis; 3, inferior margin of left sacroiliac joint;
4, left anterior superior iliac spine.
4
3
2
B
Fig. 81.3 Pre-surgical radiograph of a hip with a cam deformity of the
femoral head–neck junction (arrow). Note the loss of sphericity in the
femoral head and the loss of the tapering of the neck. (Image courtesy of
John T Heinrich MD, Milwaukee Orthopaedic Group Limited, Milwaukee,
WI, USA.)
Fig. 81.2 T1-weighted fat-saturated MR arthrogram of the left hip joint
(coronal section). The arrow points to a torn acetabular labrum at the
anterosuperior margin of the acetabulum.
The shape of the bones of the hip normally limits large and potentially create damaging impingement between the hard and bulbous femoral
damaging contact stress on adjacent connective tissues, especially neck and the softer acetabular labrum. The anterosuperior section of
during the extremes of movement. Consider, for example, the normal the labrum is particularly vulnerable to this type of injury, which is a
shape of the femoral head and neck region. Similar to the shape of a painful and often motion-limiting condition referred to as femoral-
light bulb, the spherical femoral head narrows gradually at its junction acetabular impingement syndrome. The repeatedly traumatized section
with the neck of the femur. This tapering limits large contact stress of the labrum can become enlarged, fragmented or torn. When the
between the femoral neck and the margin of the acetabulum. However, acetabular labrum is torn, a hip joint may become unstable as a con-
tapering may be lost as a result of natural variation or underlying sequence of the loss of the natural suction seal around the joint. In
pathology, resulting in a specific deformity that has been referred to as some advanced cases, the impingement trauma may create lesions at


a cam deformity because the head and neck of the femur, together, the chondrolabral junction, resulting in damage to the adjacent articu-
resemble a camshaft. Although often subtle, this deformity may be lar cartilage, potentially predisposing the hip joint to degenerative
detected radiographically (see arrow in Fig. 81.3). In some patients with arthritis (osteoarthrosis). Treatment may involve arthroscopic repair of
a cam deformity, extreme and repeated motions of the hip, typically the acetabular labrum and cartilage, as well as reshaping the area of the
involving combinations of flexion, medial rotation and adduction, can femoral head and neck responsible for the impingement. 1376.e1


Topography
1377
18
RETPAHC
circular and longitudinal. The circular fibres (zona orbicularis) are they are reinforced by the iliofemoral ligament. The capsule is also
internal and form a collar round the femoral neck; although partly strengthened inferiorly by the pubofemoral ligament, and posteriorly
blended with the pubofemoral and ischiofemoral ligaments, these by the ischiofemoral ligament. Externally the capsule is rough, covered
fibres are not directly attached to bone (see Fig. 81.4). Externally, lon- by muscles and tendons, and separated anteriorly from psoas major
gitudinal fibres are most numerous in the anterosuperior region, where and iliacus by a bursa. The capsular attachment to the femur lies
well distal to the growth plate of the femoral head both anteriorly
and posteriorly, and so the upper femoral epiphysis is entirely intrac-
Ilium apsular. The capsular attachment intersects the growth plate of the
greater trochanter on the superior surface of the base of the neck.
Ischial spine
Acetabular margin Iliocapsularis
Synovial membrane
Available with the Gray’s Anatomy e-book
Greater trochanter
Relations The joint capsule is surrounded by muscles (Fig. 81.5).
Anteriorly, lateral fibres of pectineus separate the capsule from the
femoral vein. Lateral to this, the tendon of psoas major, with iliacus
lateral to it, descends en route to the lesser trochanter, partly separated
from the capsule by a bursa. The femoral artery is anterior to the tendon
of psoas major, and the femoral nerve lies deep in a groove between
the tendon and iliacus. More laterally, the straight head of rectus femoris
crosses the joint with a deep layer of the iliotibial tract, which blends
with the capsule under the lateral border of the muscle. Superiorly, the
reflected head of rectus femoris contacts the capsule medially, while
Zona orbicularis gluteus minimus covers it laterally, being closely adherent. Inferiorly,
medial fibres of pectineus adjoin the capsule and, more posteriorly,
Ischial tuberosity


obturator externus spirals obliquely to its posterior aspect. Posteroinfe-
riorly, the capsule is covered by the tendon of obturator externus, sepa-
Lesser trochanter
rating it from quadratus femoris and accompanied by an ascending
branch of the medial circumflex femoral artery. Superior to this, the
tendon of obturator internus and the gemelli contact the joint capsule,
separating it from the sciatic nerve. The nerve to quadratus femoris is
Intertrochanteric crest
deep to the obturator internus tendon and descends medially on the
capsule. Superior to this, the posterior surface of the joint is crossed by
Fig. 81.4 Synovial cavity of the left hip joint (distended): posterior aspect. piriformis.
Gluteus medius
Anterior superior iliac spine
Tensor fasciae latae Gluteus minimus
Sartorius
Articular capsule
Rectus femoris, straight head
Acetabular labrum
Rectus femoris, reflected head
Iliacus
Piriformis
Ligament of head of femur
Obturator internus and gemelli
Psoas major tendon
Transverse acetabular ligament Gluteus maximus
Obturator externus
Pectineus
Medial circumflex femoral artery Sciatic nerve
Quadratus femoris
Obturator nerve, anterior division
Adductor longus
Adductor magnus, ischial fibres
Adductor brevis
Hamstrings
Obturator nerve, posterior division
Adductor magnus, pubic fibres
Gracilis
Fig. 81.5 Schematic dissection to display the structures surrounding the hip joint. The femoral head has been disarticulated and removed.


18
RETPAHC
Hip
Iliocapsularis (also called iliacus minor or iliotrochantericus) is a little-
known but constant muscle that lies immediately deep to the tendon
of iliopsoas and overlies the anterior hip capsule (Babst et al 2011, Ward
et al 2000). Typically present as just a few strands of fibres, it originates
from the anteromedial hip capsule and anteroinferior iliac spine, and
is attached just distal to the lesser trochanter. Although the function of
the muscle is uncertain, it may draw the capsule taut as a way of redu-
cing its impingement during hip flexion.
1377.e1


HiP
1378
9
NOiTCES
A Pubofemoral ligament Tendon of rectus femoris B Sacrospinous ligament
Obturator canal
Obturator membrane
Sacrotuberous
Reflected ligament
Tendon head
of rectus
femoris Straight
head
Descending Iliofemoral
part Iliofemoral ligament
Transverse ligament Neck
part of femur
Greater
trochanter
Ischiofemoral ligament
Lesser trochanter
Gluteal tuberosity
Greater trochanter
Lesser trochanter
Fig. 81.6 Ligaments of the hip joint. A, Anterior aspect; B, Posterior aspect. (With permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human
Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.)
Ligaments
The ligaments of the hip joint are the iliofemoral, pubof emoral,
ischiofemoral and transverse acetabular ligaments, and the ligament of
the head of the femur (Fig. 81.6). As the hip moves, the capsular liga-
ments wind and unwind, tightening around the hip, and affecting
Cut synovial membrane
stability, excursion and joint capacity (Fuss and Bacher 1991). Joint
capacity is maximal when the hip joint is held in a partially flexed and Synovial sleeve
abducted position; a patient with an effusion in the hip joint is there- around ligament
of head of femur
fore most comfortable when the joint is held in this position.
Obturator artery
Iliofemoral ligament The iliofemoral ligament is very strong and is
Pubic tubercle
shaped like an inverted Y, lying anteriorly and intimately blended with
the capsule. Its apex is attached between the anterior inferior iliac spine
Pubis
and acetabular margin, its base to the intertrochanteric line. It is com-
posed of a medially placed, thicker descending part and a laterally Acetabular branch of
placed, transverse part, which is typically distinguishable anteriorly. obturator artery
The obliquely disposed transverse part is attached to a tubercle at the Artery of ligament of


superolateral end of the intertrochanteric line, while the vertically head of femur
oriented descending part reaches the inferomedial end of the line. Ligament of head of femur
Obturator membrane
Pubofemoral ligament The pubofemoral ligament is triangular,
with a base that is attached to the iliopubic ramus, superior pubic Ischial tuberosity
ramus, obturator crest and membrane. It blends distally with the Fig. 81.7 Interior aspect of the hip joint to show the ligament of the head
capsule and deep surface of the descending part of the iliofemoral liga- of the femur. (With permission from Drake RL, Vogl AW, Mitchell A, et al
ment and has been described as consisting of multiple crura (Fuss and (eds), Gray’s Atlas of Anatomy, Elsevier, Churchill Livingstone. Copyright
Bacher 1991). 2008.)
Ischiofemoral ligament The ischiofemoral ligament thickens the
posterior aspect of the capsule. The central part spirals superolaterally
from the ischium, where it is attached posteroinferior to the acetabu- Ligament of the head of the femur The ligament of the head of
lum, then courses posterior to the femoral neck to attach distally to the the femur is a triangular and somewhat flattened band of connective
greater trochanter deep to the iliofemoral ligament. Some fibres blend tissue (see Fig. 81.5, Fig. 81.7). Its apex is attached anterosuperiorly in
with the zona orbicularis. Some of the more inferior fibres of the the fovea for the ligament of the head of the femur while its base is
ischiofemoral ligament embrace the posterior circumference of the attached principally to both edges of the acetabular notch, between
femoral neck. which it blends with the transverse acetabular ligament. It also receives
weaker contributions from the margins of the acetabular fossa, is
Transverse acetabular ligament The transverse acetabular liga- ensheathed by synovial membrane and varies in strength. Occasionally,
ment (see Fig. 80.4) is continuous peripherally with the labrum but the synovial sheath exists by itself in the absence of the ligament; rarely,


does not possess any cartilage cells. Its strong, flat fibres cross the both the ligament and sheath are absent.
acetabular notch, forming a foramen through which vessels and nerves Although the ligament of the head of the femur is known primarily
pass to enter the joint. for lending structural support to the blood vessels that travel to and


Factors maintaining stability
1379
18
RETPAHC
from the femoral head, speculation exists that it may also have a role closely by the acetabular labrum, which restrains it in the socket. In
in stabilizing the hip joint in utero. In the adult, it is mostly elongated addition, a ‘vacuum effect’ is present. The thick capsule is reinforced by
and assumed to be taut when the hip joint is semi-flexed, laterally the three major ligaments: iliofemoral, pubofemoral and ischiofemoral.
rotated, and adducted, the position where the capsular ligaments, as a The iliofemoral ligament is the strongest, and is progressively tightened
whole, offer least stability to the joint (Martin et al 2012). The degree when the femur extends to the line of the trunk. The pubofemoral and
to which the ligament of the head of the femur offers functional stabil- ischiofemoral ligaments also tighten when this happens and, as the
ity to the adult hip is uncertain, although it is likely to be secondary to joint approaches the close-packed position, resistance to an extending
that provided by the capsular ligaments and muscle activation. torque increases rapidly. The transverse acetabular ligament and liga-
Medical interest in the ligament of the head of the femur has ment of the head of the femur also contribute to stability. Only slight
increased with the advancing technology associated with medical separation of the articular surfaces can be achieved by strong traction
imaging and arthroscopic hip surgery (Botser et al 2011, Gray and Villar on the joint. To aid insertion of an arthroscope, a needle is first inserted
1997; Fig. 81.8). Free nerve endings have been identified within this into the joint to eliminate the suction effect; the joint will subsequently
ligament, suggesting that this structure may be a source of pain when open sufficiently with traction. Traumatic dislocation usually occurs
it is injured or degenerating (Leunig et al 2000). The afferent innerv- only when the joint is subjected to extreme force.
ation in the healthy state may serve as a source of proprioception or
protection of the joint (Bardakos and Villar 2009).
BIOMECHANICS OF THE HIP JOINT
Synovial membrane


The transition from quadrupedal to bipedal gait was a considerable bio-
mechanical milestone in the evolution of Homo sapiens. The biomech-
Starting from the femoral articular margin, the synovial membrane
anical features of the human lower limb, whose function is primarily
covers the intracapsular part of the femoral neck, and then passes to
to allow stance and bipedal propulsion, are very different from those of
the internal surface of the capsule to cover the acetabular labrum, the
the quadruped lower limb, and these differences are reflected in the
ligament of the head of femur and fat in the acetabular fossa. It is thin
anatomy and biomechanics of the human hip, knee, ankle and foot
on the deep surface of the iliofemoral ligament where it is compressed
joints.
against the femoral head, and sometimes is even absent here.
The acetabulum and femoral head form a multiaxial spheroidal
Bursae (‘ball and socket’) joint, which allows relatively unhindered motion in
three degrees of freedom, i.e. flexion/extension, abduction/adduction
and medial/lateral rotation. This articulation is innately limited in its
The hip joint may communicate with the subtendinous iliopectineal
capacity for translational motion in anteroposterior, transverse and
bursa through a circular aperture between the pubofemoral ligament
vertical directions.
and the descending part of the iliofemoral ligament. More distant
bursae are associated with the tendons of distal attachment of glutei Femur
medius and minimus at the greater trochanter, and between gluteus
maximus and vastus lateralis.
The femur is essentially a tubular structure with distortions that consist
of bows and twists. The most notable is the anterior bow in its mid
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE portion, where the radius of curvature is relatively constant along the
length of the femoral shaft. In the coronal (frontal) plane, the femoral
neck is inclined obliquely to the shaft at an angle of about 135° (range
Articular arteries are branches from the obturator, medial circumflex


femoral, and superior and inferior gluteal arteries; they form the cruci- 120–140°; Fig. 81.10). Although the neck–shaft angle (collo–diaphyseal
angle; Mikulicz angle) and neck length are variable, the centre of the
ate and trochanteric anastomoses (see Fig. 80.18). There is a corre-
neck in the coronal plane is at the level of the apex of the greater tro-
sponding venous drainage.
chanter. In the axial (transverse) plane, the femoral neck is anteverted,
Lymphatics from the anterior aspect of the hip joint drain to the
i.e. rotated anteriorly relative to the posterior surfaces of the femoral
deep inguinal nodes, while those from the medial and posterior aspects
of the joint travel with the obturator and gluteal arteries, respectively,
condyles; in the adult, this angle is 10–15° (Fig. 81.11A). Excessive
anteversion may exist when this angle is significantly greater than
to reach the internal iliac nodes.
10–15° (Fig. 81.11B). At birth, the angle of anteversion is typically
about 35–40°. As the child develops, forces from muscles and gravity
INNERVATION cause the angle of anteversion to decrease gradually, approaching 15°
by young adulthood. Excessive anteversion usually persists beyond
The anterior capsule of the hip joint is innervated by the femoral,
obturator and accessory obturator (when present) nerves. The poste-
rior capsule is innervated by the sciatic and superior gluteal nerves, and
by the nerve to quadratus femoris (Birnbaum et al 1997, Gardner
1948).
Head B
Hip and groin pain
N
Greater trochanter
Pain emanating from the hip and groin has many possible causes. True
Neck
pain from the hip joint is typically felt deep in the crease of the groin.
NSA
Pain over the lateral aspect of the hip usually suggests a local problem
such as trochanteric bursitis. Pain in the buttock is only occasionally
derived from the hip joint; most frequently, it is referred from the Lesser trochanter
lumbosacral spine or may be caused by vascular claudication. Pain in


the groin may be associated with inguinal or femoral hernias. In the
younger age group, it afflicts those engaged in sports, especially running
ball sports; the pain is sometimes due to femoro-acetabular impinge-
ment or to hernia but most often is related to adductor longus tendinitis Shaft
(‘groin strain’). Attritional chronic overload of the anterior abdominal
wall at its attachments to the pubis and inguinal ligament, or of external
S
oblique at the superficial inguinal ring, is a common occurrence. Rarely,
problems may occur at the pubic symphysis.
Fig. 81.10 The neck–shaft angle (NSA) between the long axis of the
femoral shaft (S) and the axis of the femoral neck (N) is on average 135°
FACTORS MAINTAINING STABILITY
(range 125–140°). In addition, in most hips, a line nearly perpendicular to
S from the tip of the greater trochanter (B) passes through the centre of
The hip joint is normally very stable. The femoral head is closely fitted the femoral head. This approximation can be utilized in judging the
to the acetabulum in an area exceeding half a sphere, and is embraced position of the femoral osteotomy in hip arthroplasty.


18
RETPAHC
Hip
The blood supply to the hip in the child is different from that in the the head of the femur. Any damage to these vessels (e.g. trauma, infec-
adult and this has very important implications clinically. Since the tion) can result in the devastating complication of avascular necrosis of
growth plate is avascular, the only blood supply to the femoral head is the femoral head. The growth plate represents a line of weakness and
conveyed through the retinacular vessels, which are mainly tributaries predisposes to fracture from injury. Acute injuries affecting the capital
of the medial circumflex femoral artery. These retinacular arteries enter epiphysis are uncommon. A more chronic fracture through the capital
the joint capsule in the trochanteric fossa and ascend the femoral neck epiphysis resulting in slipped capital femoral epiphysis, where the
on its outer aspect superiorly and posteriorly. They pass around the edge femoral head epiphysis displaces posteriorly off the femoral neck,
of the growth plate (physis) and enter the femoral head (Fig. 81.9). A occurs in pubescent adolescents, especially males (see Fig. 81.9 and
minor contribution to the vascular supply comes from the ligament of p. 1353).
Ligament of head of femur Fovea for ligament of head of femur Greater trochanter Fovea for ligament of head of femur Femoral head Transverse acetabular ligament
A B
Ligament of head of femur Acetabular fossa
Fig. 81.8 An intact ligament of the head of the femur in a left adult hip. A, T2-weighted fat-saturated MR arthrogram of the hip joint (coronal section).
(Courtesy of Michael O’Brien MD, Wisconsin Radiology Specialists, Milwaukee, WI, USA.) B, Photograph taken through an arthroscope of a slightly
distracted hip joint. (Courtesy of John T Heinrich MD, Milwaukee Orthopaedic Group Limited, Milwaukee, WI, USA.)
Fig. 81.9 Radiograph of the left hip of a 14-year-old boy. The yellow
arrow shows posterior displacement of the femoral head in the slipped
capital femoral epiphysis. The red arrow indicates the course of the
retinacular vessels along the posterior aspect of the femoral neck. The


blue arrow indicates the physis (growth plate). (Courtesy of Mr
Christopher Edward Bache.) 1379.e1


HiP
1380
9
NOiTCES
A the body passes posterior to a line joining the centres of the femoral
heads. The body therefore tends to incline posteriorly but this is coun-
terbalanced by ligamentous tension and congruence and compression
of the articular surfaces within the hip joints in the close-packed posi-
tion. Under increased loading of the trunk or leaning posteriorly, these
resistive but passive factors are assisted by active force produced by the
hip joint flexors. In swaying anteriorly at the ankles, or when the arms
are stretched forwards, and also in forward-bending at the hip, the line
of body weight moves anterior to the medial–lateral axis of rotation
through the hip joints. The posture adopted, or the rate of change of
posture, is largely controlled by the hamstrings, which, besides being
powerful flexors of the knee, are strong extensors of the hip. Gluteus
maximus becomes particularly active when the thigh is extended
15˚ against resistance, as in rising from a bending position or during
climbing.
Abduction is produced by glutei medius and minimus, assisted by
tensor fasciae latae, piriformis and sartorius. The motion is limited by
Normal anteversion adductor muscle tension, the pubofemoral ligament and the extreme
medial bands of the descending part of the iliofemoral ligament. The
B
abductor muscles, most notably glutei medius and minimus, are active
periodically at precise phases of the walking or running cycle to ensure
coronal plane stability of the pelvis.
Adduction is produced by adductors longus, brevis and magnus and
by gracilis assisted by pectineus, quadratus femoris and the inferior
fibres of gluteus maximus. The range of adduction is limited by the
increasing tension in the abductor muscles, the transverse part of the
iliofemoral ligament and the fascia lata of the thigh.
Medial rotation is produced by the anterior fibres of glutei minimus
and medius, and assisted by tensor fasciae latae and most adductor
muscles. The strength of medial rotation naturally increases as the hip
is flexed because this position increases the moment arm of most
medial rotator muscles (Delp et al 1999). Medial rotation is limited


by tension in lateral rotator muscles such as piriformis, the ischiofem-
35˚
oral ligament and the adjacent posterior joint capsule (Wagner et al
2012).
Excessive anteversion Lateral rotation is produced by gluteus maximus, obturator internus,
superior and inferior gemelli, quadratus femoris and piriformis, and it
Fig. 81.11 A, Superior view of a proximal femur with normal anteversion.
B, Superior view of a proximal femur with excessive anteversion. (With is assisted by obturator externus and sartorius. Lateral rotation, a
permission from Neumann D, Kinesiology of the Musculoskeletal System, stronger motion than medial rotation, is limited by tension in the
2nd ed, Elsevier, Mosby. Copyright 2010.) medial rotator muscles and the transverse part of the iliofemoral liga-
ment (Myers et al 2011).
Forces acting on the hip
childhood in cases of abnormal motor development, such as can be
seen with cerebral palsy.
The degree of anteversion affects many aspects of lower limb bio- In quiet upright standing, the femoral heads support the weight of the
mechanics, including the moment (lever) arms of the hip abductor and trunk, upper limbs and head. About two-thirds of body weight is
medial rotator muscles (the perpendicular distance from the centre of located above the hips, and so each femoral head normally accepts
rotation of the femur to the line of action of the resultant muscle force); about one-third of body weight. This force is compressive in nature, as
patellar tracking (the motion of the patella relative to the femur); and gravity pulls the acetabula against the femoral heads. When viewed in
foot orientation. the sagittal plane, minimal muscle forces suffice to maintain equilib-
rium as long as the weight of the upper body is directed over the femoral
Acetabulum heads. If the upper body leans anteriorly, shifting the upper body weight
vector anteriorly beyond the femoral heads and thereby producing a
hip flexion moment, posterior thigh muscles can counter such rotation.
The acetabulum consists of the confluence of the ilium, ischium and
As the capsular ligaments of the hip slacken in flexion, none of them


pubis at the triradiate cartilage. By itself, the acetabulum covers an area
is able to resist the forward lean.
slightly less than a hemisphere; it is deepened by the acetabular labrum.
During walking, hip joint compression force varies from one-third
The degree of acetabular anteversion is about 17° (16° males and 18°
of body weight, when both feet are on the ground, to some four times
females) (Reikeras et al 1983). In the coronal plane, the acetabular axis
body weight when the other foot is lifted. The large compression forces
is inclined inferiorly approximately 45° from the horizontal.
generated while walking originate primarily from two sources: gravity
and muscle activation. During the stance phase, gravity pulls the upper
MOVEMENTS body and acetabulum inferiorly on the femoral heads (as described
above for quiet standing). More significantly, each femoral head is
pushed superiorly against its socket as the foot strikes and then pushes
Available with the Gray’s Anatomy e-book against the ground. Although activation of muscles is responsible for a
greater portion of joint compression at the hip, the influences of gravity
Muscles producing hip joint movements
and of capsular tension (when the hip joint is extended) should not be
ignored.
Flexion is primarily produced by psoas major, iliacus and rectus femoris, As the lower limb is swinging anteriorly and free of contact with the
assisted by pectineus, tensor fasciae latae and sartorius. The adductors, ground, hip joint compression force is estimated to be at about 50%
particularly adductor longus and brevis, also assist, especially when the of body weight (Correa et al 2010). Such joint force is essentially myo-
hip is near full extension. Effective action of the hip flexor muscles genic. Consider, for example, a contracting iliopsoas pulling the femoral
requires strong synergistic activation of the abdominal muscles to sta- head against the acetabulum as it simultaneously advances the lower
bilize the pelvis. limb in walking.
Extension is produced by gluteus maximus, biceps femoris, semi- In contrast, during the stance phase of walking, hip joint forces may


tendinosus, semimembranosus and adductor magnus. The posterior reach four times body weight. These forces are mainly caused by the
fibres of gluteus medius assist with this action (Neumann 2010a). In pull of the hip abductor muscles (primarily gluteus medius, gluteus
the fully erect posture, a vertical line through the centre of gravity of minimus and tensor fasciae latae). This muscular action, essential to


18
RETPAHC
Hip
Two terms can conveniently describe the kinematics (movements) at stationary femoral heads (compare Figs 81.12A and B). Depending on
the hip. Femoral-on-pelvic hip kinematics describes the rotation of the the accompanying trunk movement, the lumbar vertebrae will either
femur about a relatively fixed pelvis. Conversely, pelvic-on-femoral flex or extend in rhythm with the rotating pelvis. Consider, for example,
(hip) kinematics describes the rotation of the pelvis, and often the a short-arc anterior rotation (or tilt) of the pelvis over both femurs while
superimposed trunk, over a relatively fixed femur or set of femurs. the upper trunk remains stationary. During this motion, the lumbar
Regardless of whether the femur or the pelvis is the moving segment, vertebrae extend slightly towards greater lordosis. By comparison, rotat-
kinematics are described for all three cardinal planes on the assumption ing both the pelvis and the trunk over both femurs (as in reaching
that movements are initiated from the anatomical position. towards the ground with knees held extended), the pelvis and the tho-
Flexion and extension are motions that occur in the sagittal plane. racolumbar vertebrae both flex, thereby augmenting the overall forward
To appreciate the hip joint arthrokinematics that accompany the associ- motion of the body as a whole.
ated femoral-on-pelvic motions, the length and angulation of the Abduction and adduction of the hip joint occur in the coronal plane
femoral neck in relation to the shaft must be considered. As the hip about an anterior-to-posterior axis of rotation through the femoral
(femur) is flexed about 120° towards the anterior thoracic wall, or head. With the pelvis fixed, the femur abducts about 40° (Fig. 81.13A).
extended 10–20° beyond the plane of the trunk, the femoral head Conversely, pelvic-on-femoral (hip) motions that occur in the coronal
‘spins’ in the acetabulum about a side-to-side (medial–lateral) axis of
rotation. Conversely, from a pelvic-on-femoral perspective, the acetab-
ula rotate around a similar axis in flexion and extension relative to A
A Flexion
Slack iliofemoral Abduction


ligament
Pubofemoral ligament
Adductor brevis
Adductor longus
Gluteus
maximus
40˚
120˚
Inferior
capsule
B
Abduction
B
Intertransverse ligament
Flexion
(Anterior pelvic tilt) 30˚
Pubofemoral ligament
Slack iliofemoral
ligament Adductor brevis
30˚
Adductor longus
Biceps femoris
Fig. 81.12 Hip flexion shown from two kinematic perspectives, as
indicated by the green curved arrows. A, Femoral-on-pelvic flexion. Fig. 81.13 Hip abduction shown from two kinematic perspectives, as
B, Pelvic-on-femoral flexion. Note the directional-specific motion of the indicated by the green curved arrows. A, Femoral-on-pelvic abduction.
lumbar spine in B; this is a necessity, assuming the trunk remains upright. B, Pelvic-on-femoral abduction. Note the directional-specific motion of
Tissues that are elongated or pulled taut are indicated by orange arrows; the lumbar spine in B; this is a necessity, assuming the trunk remains
tissues slackened are indicated by blue wavy arrows. In all cases, upright. Tissues that are elongated or pulled taut are indicated by orange
muscles are assumed to be inactive but stretched. The red circle arrows. In all cases, muscles are assumed to be inactive but stretched.
indicates the axis of rotation at the hip. (With permission from Neumann The red circle indicates the axis of rotation at the hip. (With permission
D, Kinesiology of the Musculoskeletal System, 2nd ed, Elsevier, Mosby. from Neumann D, Kinesiology of the Musculoskeletal System, 2nd ed,
Copyright 2010.) Elsevier, Mosby. Copyright 2010.) 1380.e1


9
NOiTCES
HiP
Adduction
Intertransverse
ligament Tensor fasciae latae
25˚ and iliotibial tract
Gluteus medius
Erector spinae
Transversospinalis
Gluteus medius
(posterior fibres)
Piriformis
Obturator internus
Quadratus femoris
Gluteus maximus
Fig. 81.14 Hip adduction shown from a pelvic-on-femoral perspective, as
indicated by the green curved arrow. Note the directional-specific motion
of the lumbar spine; this is a necessity, assuming the trunk remains
upright. Tissues that are elongated or pulled taut are indicated by orange
arrows. In all cases, muscles are assumed to be inactive but stretched. Fig. 81.15 The right lateral rotator muscles of the hip contract to produce
The red circle indicates the axis of rotation at the hip. (With permission lateral rotation of the right hip, from a pelvic-on-femoral perspective.
from Neumann D, Kinesiology of the Musculoskeletal System, 2nd ed, Back extensor muscles are also shown active, rotating the lower trunk
Elsevier, Mosby. Copyright 2010.) to the left. (With permission from Neumann D, Kinesiology of the
Musculoskeletal System, 2nd ed, Elsevier, Mosby. Copyright 2010.)
plane are best described assuming a person is bearing weight firmly on fixed, the femur rotates medially about 35°. The extended hip rotates
one lower limb, referred to hereafter as the ‘support’ hip. Abduction at laterally about 45°. Transverse plane movements of the hip joint from
the support hip occurs by raising the contralateral side of the pelvis a a pelvic-on-femoral perspective, as explained above, are best described
few degrees (Fig. 81.13B). Marked tightness in hip adductor muscles or assuming a person is bearing weight over a given ‘support’ hip. Con-
medial capsule of the hip on the support hip can limit this pelvic sider, for example, running and rapidly changing directions while one
motion. Adduction at the support hip occurs by lowering the contra- lower limb is securely planted on the ground. During lateral rotation


lateral side of the pelvis (Fig. 81.14). Assuming that the trunk remains of the support hip, the iliac crest located contralateral to the support
nearly stationary during these short-arc pelvic-on-femoral motions, the limb rotates posteriorly in the transverse plane, an action driven strongly
lumbar spine laterally bends slightly as a way to offset undesired tho- by gluteus maximus (Fig. 81.15). Conversely, pelvic-on-femoral (hip)
racic motion. The lumbar vertebrae, therefore, act to decouple motion medial rotation occurs as the contralateral iliac crest region rotates
of the pelvis (moving on the femur) from undesired motions between anteriorly.
the thorax and pelvis (Neumann 2010b). This decoupling function of As stated above, the axis of rotation for transverse plane motions at
the lumbar vertebrae is especially useful during walking as a way of the hip joint occurs about a vertical axis of rotation. The slight anterior
partially fixing the spatial orientation of the upper thorax, as well as the bowing for the femoral shaft, coupled with the natural angle between
associated craniocervical region and the embedded senses of vision and the femoral shaft and neck, means that this axis is not intramedullary;
equilibrium. This kinematic linkage between the spine, pelvis and rather it passes just posterior and slightly medial to the shaft. The posi-
femur exists in essentially all hip motions to varying degrees, and is an tion of this ‘mechanical’ (versus medullary) axis becomes biomechani-
essential characteristic of normal walking. cally relevant when considering the actions and moment arms of certain
Medial and lateral rotation of the hip joint occurs in the transverse hip muscles, most notably for adductor muscles that also function as
(horizontal) plane about a vertical axis of rotation. With the pelvis medial rotators.
1380.e2


Key references
1381
18
RETPAHC
Counterclockwise moment Clockwise moment left hip abductor force (Ab) is about half the length of the lever arm
(BW x b) (Ab x a) (b) associated with body weight (BW). To balance the competing
(coronal plane) gravitational moments about the stance hip, the hip
abductors must produce a force about twice superincumbent body
= weight. Thus, the acetabulum is pulled inferiorly against the femoral
head not only by the body weight but also by the force created by the
activated hip abductor muscles. The sum of the muscular and gravit-
ational forces equals about 2.5 times the total weight of the person.
These downward forces on the head of the femur are counteracted by
an upward joint reaction force of equal magnitude (JRF in Fig. 81.16).
Both magnitude and direction of the joint reaction force are strongly
influenced by the pull of the hip abductor muscles.
The above analysis is for standing quietly on one limb. During
Ab
walking, however, the joint reaction force routinely reaches at least four
times body weight, reflecting both the high ground reaction forces and
the need for the hip abductor muscles to decelerate rotations of the
a pelvis (Bergmann et al 1993). Hip joint forces reach still greater values
b during running or stair-climbing (see review in Stansfield and Nicol
2002).
Compression forces produced by the gluteus medius during stance
phase are directed superiorly and slightly anteromedially within the
acetabulum (Correa et al 2010), a region naturally protected by thick
articular cartilage. In the healthy hip joint, the muscular-based compres-
sive forces serve important functions, such as helping to stabilize the
JRF
articulation and stimulate the morphological development of the
BW growing hip. Forces that cross the hip typically do not harm the joint
because they are absorbed by healthy articular cartilage and congruent
joint surfaces. Failure of these conditions to absorb forces in the joint
Fig. 81.16 While standing on one (left) lower limb, body weight (BW) line may predispose to osteoarthritis of the hip.
of force, i.e. total body weight minus the weight of the left lower limb, The three factors that influence both the magnitude and the direc-


passes just lateral to the midline, exerting a counterclockwise moment tion of compressive forces acting on the hip are the position of the
about the stance hip (BW × b). An equal but clockwise moment is centre of gravity; the abductor moment arm, which is a function of neck
required about the stance hip for mechanical equilibrium: a moment length (offset) and neck–shaft angle; and the amount of body weight.
produced by the force of the abductors (Ab), whose lever arm (a) is Shortening of the lever arm of the abductors, such as occurs in coxa
approximately half that of the lever arm (b). The two moments are in valga or excessive femoral anteversion, or in a remodelled proximal
balance when (Ab × a = BW × b). The abductor force required to maintain femur in advanced hip osteoarthritis, would increase abductor muscle
equilibrium is approximately twice that of BW, resulting in a joint reaction demand and thus increase joint reaction force as well. If the muscles
force (JRF) about 2.5 times that of total weight of the subject’s body. cannot meet this demand, the pelvis cannot be held level in standing
on one limb, a problem known as either a compensated or an uncom-
normal bipedal gait, provides the necessary coronal plane stabilization pensated Trendelenburg sign. The Trendelenburg sign is said to be
of the pelvis relative to the femoral head of the stance limb. compensated if the pelvis is brought towards the affected stance limb
The importance of hip abductor muscle activation during the stance as a way of shortening the body weight’s lever arm. Conversely, the
phase of walking can be well appreciated by understanding the simple Trendelenburg sign is said to be uncompensated if the pelvis drops away
mechanics of standing on one limb (Fig. 81.16). The lever arm (a) of from the affected stance limb uncontrollably.
Bonus e-book images
Fig. 81.1B Anteroposterior radiograph of an Fig. 81.8 An intact ligament of the head of Fig. 81.14 Hip adduction shown from a
adult male pelvis. the femur in a left adult hip. pelvic-on-femoral perspective.
Fig. 81.9 Radiograph of the left hip of a Fig. 81.15 The right lateral rotator muscles


Fig. 81.2 T1-weighted fat-saturated MR
14-year-old boy. of the hip contract to produce lateral
arthrogram of the left hip joint (coronal
rotation of the right hip, from a pelvic-on-
section).
Fig. 81.12 Hip flexion shown from two femoral perspective.
kinematic perspectives.
Fig. 81.3 Pre-surgical radiograph of a hip Imaging slideshow 81.1 Hip arthroscopy.
with a cam deformity of the femoral Fig. 81.13 Hip abduction shown from two
head–neck junction. kinematic perspectives.
KEY REFERENCES
Botser IB, Martin DE, Stout CE et al 2011 Tears of the ligamentum teres: A dynamic optimization (computerized) approach used to determine the
prevalence in hip arthroscopy using 2 classification systems. Am J Sports contributions of individual hip muscles to the total joint contact forces on a
Med 39:Suppl-25S. normal hip while walking.
The prevalence of tears of the ligamentum teres in a population of patients
Delp SL, Hess WE, Hungerford DS et al 1999 Variation of rotation moment
who underwent hip arthroscopy.
arms with hip flexion. J Biomech 32:493–501.
Correa TA, Crossley KM, Hyung JK et al 2010 Contributions of individual An estimation of the moment arm length in several hip muscles as a
muscles to hip joint contact force in normal walking. J Biomech 43: function of range of motion, based on a three-dimensional computer model
1618–22. and experimental measurements from cadaveric hips.


HiP
1382
9
NOiTCES
Ferguson SJ, Bryant JT, Ganz R et al 2003 An in vitro investigation of the Neumann DA 2010a The actions of hip muscles. J Orthop Sports Phys Ther
acetabular labral seal in hip joint mechanics. J Biomech 36:171–8. 40:82–94.
A biomechanical study of how the acetabular labrum pressurizes and seals A review of the interactions among the muscles that cross the hip joint, with
the hip joint using human cadaveric material. particular reference to how these interactions influence normal movement
and physical rehabilitation of the lower limb.
Fuss FK, Bacher A 1991 New aspects of the morphology and function of the
human hip joint ligaments. Am J Anat 192:1–13. Safran MR, Giordano G, Lindsey DP et al 2011 Strains across the acetabular
An examination of how the motion of the hip affects the length and labrum during hip motion: a cadaveric model. Am J Sports Med 39:
subsequent stretch on the hip capsular ligaments in dissected, cadaveric hips. Suppl-102S.
A cadaveric study correlating the circumference strain placed across the
Leunig M, Beck M, Stauffer E et al 2000 Free nerve endings in the ligamen-
entire acetabular labrum with different hip motions.
tum capitis femoris. Acta Orthop Scand 71:452–4.
An immunohistochemical study of free nerve endings in the ligamentum Wagner FV, Negrao JR, Campos J et al 2012 Capsular ligaments of the hip:
teres (capitis femoris). anatomic, histologic, and positional study in cadaveric specimens with
MR arthrography. Radiology 263:189–98.
Martin RL, Palmer I, Martin HD 2012 Ligamentum teres: a functional
An evaluation using MRI and dissection of the length and subsequent
description and potential clinical relevance. Knee Surg Sports Traumatol
tension in the capsular ligaments of the hip in ten cadaveric specimens at
Arthrosc 20:1209–14.
the extremes of extension, flexion, abduction, adduction, and medial and


Use of a string model of the ligamentum teres to rank the relative length
lateral rotation.
changes in the structure at different hip positions.


18
RETPAHC
Hip
REFERENCES
Babst D, Steppacher SD, Ganz R et al 2011 The iliocapsularis muscle: an Leunig M, Beck M, Stauffer E et al 2000 Free nerve endings in the ligamen-
important stabilizer in the dysplastic hip. Clin Ortho Rel Res 469: tum capitis femoris. Acta Orthop Scand 71:452–4.
1728–34. An immunohistochemical study of free nerve endings in the ligamentum
Bardakos NV, Villar RN 2009 The ligamentum teres of the adult hip. J Bone teres (capitis femoris).
Joint Surg Br 91:8–15. Martin RL, Palmer I, Martin HD 2012 Ligamentum teres: a functional
Bergmann G, Graichen F, Rohlmann A 1993 Hip joint loading during walk- description and potential clinical relevance. Knee Surg Sports Traumatol
ing and running, measured in two patients. J Biomech 26:969–90. Arthrosc 20:1209–14.
Birnbaum K, Prescher A, Hessler S et al 1997 The sensory innervation of the Use of a string model of the ligamentum teres to rank the relative length
hip joint – an anatomical study. Sur Radiol Anat 19:371–5. changes in the structure at different hip positions.
Botser IB, Martin DE, Stout CE et al 2011 Tears of the ligamentum teres: Myers CA, Register BC, Lertwanich P et al 2011 Role of the acetabular labrum
prevalence in hip arthroscopy using 2 classification systems. Am J Sports and the iliofemoral ligament in hip stability: an in vitro biplane fluor-
Med 39:Suppl-25S. oscopy study. Am J Sports Med 39:Suppl-91S.
The prevalence of tears of the ligamentum teres in a population of patients Neumann DA 2010a The actions of hip muscles. J Orthop Sports Phys Ther
who underwent hip arthroscopy. 40:82–94.
Cadet ER, Chan AK, Vorys GC et al 2012 Investigation of the preservation Neumann DA 2010b Kinesiology of the Musculoskeletal System: Founda-


of the fluid seal effect in the repaired, partially resected, and recon- tions for Physical Rehabilitation, 2nd ed. St Louis: Elsevier.
structed acetabular labrum in a cadaveric hip model. Am J Sports Med A review of the interactions among the muscles that cross the hip joint, with
40:2218–23. particular reference to how these interactions influence normal movement
Correa TA, Crossley KM, Kim HJ et al 2010 Contributions of individual and physical rehabilitation of the lower limb.
muscles to hip joint contact force in normal walking. J Biomech Reikeras O, Bjerkreim I, Kolbenstvedt A 1983 Anteversion of the acetabulum
43:1618–22. and femoral neck in normals and in patients with osteoarthritis of the
A dynamic optimization (computerized) approach used to determine the hip. Acta Orthop Scand 54:18–23.
contributions of individual hip muscles to the total joint contact forces on a
Safran MR, Giordano G, Lindsey DP et al 2011 Strains across the acetabular
normal hip while walking.
labrum during hip motion: a cadaveric model. Am J Sports Med 39:
Delp SL, Hess WE, Hungerford DS et al 1999 Variation of rotation moment Suppl-102S.
arms with hip flexion. J Biomech 32:493–501. A cadaveric study correlating the circumference strain placed across the
An estimation of the moment arm length in several hip muscles as a entire acetabular labrum with different hip motions.
function of range of motion, based on a three-dimensional computer model
Song Y, Ito H, Kourtis L et al 2012 Articular cartilage friction increases in
and experimental measurements from cadaveric hips.
hip joints after the removal of acetabular labrum. J Biomech 45:
Ferguson SJ, Bryant JT, Ganz R et al 2003 An in vitro investigation of the 524–30.
acetabular labral seal in hip joint mechanics. J Biomech 36:171–8. Stansfield BW, Nicol AC 2002 Hip joint contact forces in normal subjects
A biomechanical study of how the acetabular labrum pressurizes and seals and subjects with total hip prostheses: walking and stair and ramp


the hip joint using human cadaveric material. negotiation. Clin Biomech 17:130–9.
Fuss FK, Bacher A 1991 New aspects of the morphology and function of the Wagner FV, Negrao JR, Campos J et al 2012 Capsular ligaments of the hip:
human hip joint ligaments. Am J Anat 192:1–13. anatomic, histologic, and positional study in cadaveric specimens with
An examination of how the motion of the hip affects the length and MR arthrography. Radiology 263:189–98.
subsequent stretch on the hip capsular ligaments in dissected, cadaveric hips. An evaluation using MRI and dissection of the length and subsequent
tension in the capsular ligaments of the hip in ten cadaveric specimens at
Gardner E 1948 The innervation of the hip joint. Anat Rec 101:353–71.
the extremes of extension, flexion, abduction, adduction, and medial and
Gray AJ, Villar RN 1997 The ligamentum teres of the hip: an arthroscopic lateral rotation.
classification of its pathology. Arthroscopy 13:575–8.
Ward WT, Fleisch ID, Ganz R 2000 Anatomy of the iliocapsularis muscle.
Kim YT, Azuma H 1995 The nerve endings of the acetabular labrum. Clin
Relevance to surgery of the hip. Clin Ortho Rel Res 374:278–85.
Orthop 320:176–81.
1382.e1


CHAPTER
82
Knee
The knee is the largest synovial joint in the body. It consists of three ligament (overlying the posterior surface of the capsule of the knee
functional compartments that collectively form a dynamic, specialized joint), and the posterior aspect of the proximal tibia covered by popli-
hinge joint. During propulsion, the knee is able to withstand impressive teus and its fascia. The deep fascia (fascia musculorum) acts as the roof
weight-bearing loads while conducting precision movements, providing of the fossa and is continuous with the fascia lata proximally and with
a stable yet fluid mechanism for relatively efficient bipedal locomotion. the deep fascia of the leg distally. It is a dense layer that is strongly
The complex arrangement of intra- and extracapsular ligaments that reinforced by transverse fibres and is often perforated by the short
helps to counter the considerable biomechanical demands that are saphenous vein and medial and lateral sural cutaneous nerves; these
imposed on the joint can also be involved in disease (i.e. tri- structures are useful landmarks in the direct posterior approach to the
compartment disease). knee joint.
The popliteal fossa is approximately 2.5 cm wide. Distally, its con-
tents are protected and hidden by the heads of gastrocnemius, which
SKIN AND SOFT TISSUES
contact each other. The fossa contains the popliteal vessels (see Fig.
82.2; Fig. 82.4), tibial and common fibular nerves, short saphenous
SKIN vein, medial and lateral sural cutaneous nerves, posterior femoral cuta-
neous nerve, articular branch of the obturator nerve, lymph nodes, fat
Innervation and a variable number of bursae. The tibial nerve descends centrally
immediately anterior to the deep fascia, crossing the vessels posteriorly
Infrapatellar branch of the saphenous nerve from lateral to medial. The common fibular nerve descends laterally
immediately medial to the tendon of biceps femoris. When the pop-
The infrapatellar branch of the saphenous nerve reaches the anterior
liteal vessels enter the proximal region of the popliteal fossa, they
aspect of the knee from the medial side. It is invariably divided in the
maintain a side-by-side relationship, which shifts to an over–under


medial surgical approaches to the knee, which accounts for the numb-
relationship as they descend through the fossa and are held together by
ness that inevitably occurs following such procedures. A painful
dense areolar tissue within the fossa. This may potentially compromise
neuroma may form if the nerve is partially sectioned, e.g. by the incision
the popliteal artery in distal femoral fractures. The popliteal vein is
for an arthroscopy portal or a small medial arthrotomy. Unfortunately,
generally located posterior to the artery. Proximally, the vein lies lateral
the position of the nerve relative to the line of the joint is variable. In
to the artery, crossing to its medial side distally. At times, the popliteal
most cases, it crosses just below the joint line, passing over the patellar
vein may be duplicated, so that the artery lies between the veins, which
ligament at its insertion on to the tibia. For further details, see Tennant
are usually bridged by connecting channels. An articular branch from
et al (1998).
the obturator nerve descends along the artery to the knee. Six or seven
Peripatellar plexus popliteal nodes are embedded in the fat, one under the deep fascia near
the termination of the short saphenous vein, one between the popliteal
Proximal to the knee, the infrapatellar branch of the saphenous nerve
artery and knee joint, and the others intimate with the popliteal vessels.
connects with branches of the medial and intermediate femoral cutan-
eous nerves, and lateral femoral cutaneous nerve. Distal to the knee, it
connects with other branches of the saphenous nerve. This fine, subcu-
taneous network of communicating nerve fibres over and around the Descending
patella is termed the peripatellar plexus. genicular artery
Descending branch
Articular branch of
of lateral
Cutaneous vascular supply descending genicular
circumflex femoral
artery
and lymphatic drainage artery
Saphenous branch
The arterial supply of the skin covering the knee is derived from genicu- of descending
genicular artery
lar branches of the popliteal artery, the descending genicular branch of
the femoral artery, and the anterior recurrent branch of the anterior Superior medial Superior lateral


tibial artery, with small contributions from muscular branches to vastus genicular artery genicular artery
medialis and the posterior thigh muscles (Fig. 82.1). For further details,
consult Cormack and Lamberty (1994).
Tibial collateral Fibular collateral
Cutaneous veins are tributaries of vessels that correspond to the ligament ligament
named arteries. Cutaneous lymphatic drainage is initially to the super-
Patellar ligament
ficial inguinal nodes, possibly also to the popliteal nodes, and then to
Inferior lateral
the deep inguinal nodes. Inferior medial genicular artery
genicular
artery
SOFT TISSUES
Circumflex
Popliteal fossa fibular artery
The popliteal fossa (Figs 82.2–82.3) is a diamond-shaped region pos- Anterior tibial
terior to the knee, bordered by posterior compartment muscles of the recurrent artery
thigh and leg. The boundaries are biceps femoris proximolaterally;
Anterior
semimembranosus and the overlying semitendinosus proximomedi-
tibial artery
ally; the lateral head of gastrocnemius with the underlying plantaris
distolaterally; and the medial head of gastrocnemius distomedially. The
anterior boundary (or floor) of the fossa is formed, in proximodistal Fig. 82.1 The arterial anastomoses around the left knee joint, anterior
sequence, by the popliteal surface of the femur, the oblique popliteal aspect. 1383


Knee
1384
9
nOITCeS
Biceps femoris Semitendinosus
Biceps
femoris Gracilis Plantaris Semimembranosus
Gracilis
Femur, popliteal surface
Semitendinosus
Tendon of semitendinosus
Semimembranosus
Tendon of semimembranosus
Tibial nerve
Gastrocnemius, lateral head Gastrocnemius, medial head
Common fibular Popliteal vein
nerve
Popliteal artery
Superior lateral
genicular artery
Lateral sural Superior medial
cutaneous genicular artery
nerve
Short saphenous
vein
Sural arteries
Muscular branches
Medial sural of tibial nerve
cutaneous
nerve
Tendon of Soleus
biceps femoris
Soleus
Gastrocnemius, Gastrocnemius,
lateral head medial head Tendon of gastrocnemius
Tendon of plantaris
Fig. 82.2 The left popliteal fossa. (With permission from Waschke J,
Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th ed, Elsevier,
Urban & Fischer. Copyright 2013.) Fascia of leg
Medial malleolus
BONES
Lateral malleolus Calcaneal tendon
FEMUR, TIBIA AND FIBULA
The femur is described on pages 1348–1353 and the tibia and fibula Calcaneal tuberosity
are described on pages 1401–1405 and 1405, respectively.
PATELLA
Fig. 82.3 Muscles of the calf, superficial view including the boundaries of
The patella is the largest sesamoid bone in the body (Figs 82.5–82.6) the popliteal fossa. (With permission from Waschke J, Paulsen F (eds),
and is embedded in the tendon of quadriceps femoris, lying anterior to Sobotta Atlas of Human Anatomy, 15th ed, Elsevier, Urban & Fischer.
the distal femur (femoral condyles). It is flat, distally tapered and proxi- Copyright 2013.)
mally curved, and has anterior and articular surfaces, three borders and
an apex, which is the distal end of the bone. Most surfaces and borders


are palpable. With the knee in extension, the apex is positioned proxi- retinaculum receives contributions from the iliotibial tract. Ossification
mal to the line of the knee joint by 1–2 cm. occasionally extends from the lateral margin of the patella into the
The subcutaneous, convex anterior surface is perforated by numer- tendon of vastus lateralis.
ous nutrient vessels. It is longitudinally ridged, separated from the skin The shape of the patella can vary and certain configurations are
by the subcutaneous prepatellar bursa, and covered by an expansion associated with patellar instability. Not infrequently, a bipartite and,
from the tendon of quadriceps femoris, which blends distally with less commonly, a tripartite patella are seen on imaging. The bone seems
superficial fibres of the patellar ligament (inaccurately named because to be in separate parts, usually with a smaller superolateral fragment:
this structure is the continuation of the tendon of quadriceps femoris). this has long been attributed to the presence of a separate ossification
The posterior surface has a proximal smooth, oval articular area, crossed centre but, in some cases, could represent failed union following either
by a smooth vertical ridge, which fits the intercondylar groove on the a stress fracture or a violent contraction of quadriceps femoris (e.g.
femoral patellar surface and divides the patellar articular area into landing on the feet after jumping from a substantial height) resulting
medial and lateral facets; the lateral is usually larger. Each facet is in a traumatic fracture.
divided by faint horizontal lines into approximately equal thirds. A
seventh ‘odd’ facet is present as a narrow strip along the medial border Structure The patella consists of more or less uniformly dense trabec-
of the patella; it contacts the medial femoral condyle in extreme knee ular bone, covered by a thin compact lamina. Trabeculae beneath the
flexion. Distal to the articular surface, the apex is roughened by the anterior surface are parallel to the surface; elsewhere, they radiate from
attachment of the patellar ligament. Proximal to this, the area between the articular surface into the substance of the bone.
the roughened apex and the articular margin is covered by an infrapatel-


lar fat pad. The patellar articular cartilage is the thickest in the body, Muscle attachments Quadriceps femoris is attached to the superior
reflecting the magnitude of the stresses to which it is subjected. surface, except near its posterior margin; the attachment extends distally
The thick superior border (surface) slopes anteroinferiorly. The on to the anterior surface. The attachment for rectus femoris is antero-
medial and lateral borders are thinner and converge distally; the inferior to that for vastus intermedius. Rough markings can be traced
expansions of the tendons of vasti medialis and lateralis (medial and in continuity around the periphery of the bone from the anterosuperior
lateral patellar retinacula, respectively) are attached to them. The lateral surface to the deep surface of the apex. Those at the lateral and medial


Joints
1385
28
ReTPAHC
Tibial nerve Popliteal artery 4
Plantaris Inferior medial genicular artery
1
Popliteus
Anterior tibial artery
5
Soleus Soleus
Tibialis posterior
Fibular artery
Posterior tibial artery
2
6
3
Tibial nerve
A
Flexor digitorum longus 1
4
Fibularis longus
Flexor hallucis longus
5
6
2
Posterior tibial artery 7
Fibularis brevis
Tendon of tibialis posterior
3
Medial malleolar branches
Lateral malleolar 8
Tendon of flexor hallucis longus
branches
Calcaneal tendon
9
B
Calcaneal branches
Calcaneal anastomosis
Fig. 82.5 A, Left patella, anterior aspect. Key: 1, area of attachment of
rectus femoris; 2, medial border: attachment of medial retinaculum
(expansion); 3, apex; 4, area of attachment of vastus intermedius; 5,
markings of attachment of tendon of quadriceps femoris; 6, lateral border:
attachment of lateral retinaculum (expansion). B, Left patella, articular
Fig. 82.4 The left popliteal, posterior tibial and fibular arteries, posterior (posterior) surface. Key: 1, upper lateral facet: in contact with femur in
aspect. (With permission from Waschke J, Paulsen F (eds), Sobotta Atlas flexion of the knee; 2, lower lateral facet: in contact with femur in
of Human Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.) extension of the knee; 3, area overlain by edge of circumferential fat pad;
4, upper medial facet: in contact with femur in flexion of the knee; 5,
medial vertical (‘odd’) facet: in contact with femur in extreme flexion of
borders represent the attachments of vasti lateralis and medialis, and the knee; 6, lower medial facet: in contact with femur in extension of the


those at the apex represent the attachment of the patellar ligament. knee; 7, ridge; 8, area covered by infrapatellar fat pad; 9, area for
attachment of patellar ligament.
Vascular supply The arterial supply of the patella is derived from
the genicular anastomosis, particularly from the genicular branches of
the popliteal artery and from the anterior tibial recurrent artery. An latter case, the joint surfaces are inclined at an angle of greater than
anatomical study in children and fetuses confirmed that this network 20°). The fibular facet is usually elliptical or circular, and almost flat or
is already well developed in these age groups (Hamel et al 2012). slightly grooved. The surfaces are covered with hyaline cartilage.
The volume of articular cartilage peaks at Tanner stage 2; boys gain
Ossification Several centres appear during the third to sixth years and articular cartilage faster than girls. The rate of cartilaginous volume
these coalesce rapidly. Accessory marginal centres appear later and fuse development is +233 µl/year for the patella, +350 µL/year for the
with the central mass. medial tibial compartment and +256 µL/year for the lateral tibial com-
partment (Jones et al 2003).
JOINTS
Fibrous capsule The capsule is attached to the margins of the articu-
lar surfaces of the tibia and fibula, and is thickened anteriorly and
SUPERIOR TIBIOFIBULAR JOINT posteriorly.
The superior (proximal) tibiofibular joint is a synovial joint (plane Ligaments The ligaments of the superior tibiofibular joint are not
variety) between the lateral tibial condyle and head of the fibula. entirely separate from the capsule. The anterior ligament is made up of
two or three flat bands, which pass obliquely up from the fibular head
Articulating surfaces The articulating surfaces vary in size, form to the front of the lateral tibial condyle in close relation to the tendon
and inclination. The joint line may be transverse or oblique (in the of biceps femoris. The posterior ligament is a thick band that ascends


Knee
1386
9
nOITCeS
2
1
1
2
3
3
2
2
4 4
2
A B
Fig. 82.6 Anteroposterior (A) and lateral (B) radiographs of the knee of a boy aged 14 years. Key: 1, patella; 2, cartilaginous growth plates;
3, intercondylar eminence; 4, prolongation of proximal tibial epiphysis and growth plate forming the tibial tuberosity.
obliquely between the posterior aspect of the fibular head and the flexion, when the highest lateral patellar facet contacts the anterior part
lateral tibial condyle, covered by the popliteal tendon. of the lateral femoral condyle. As the knee extends, the middle patellar
facets contact the lower half of the femoral surface; in full extension,
Synovial membrane The synovial membrane of the superior tibio- only the lowest patellar facets are in contact with the femur. In summary,
fibular joint is occasionally continuous with that of the knee joint via on flexion, the patellofemoral contact point moves proximally and the
the subpopliteal recess. contact area broadens to cope with the increasing stress that accompa-
nies progressive knee flexion.
Vascular supply and lymphatic drainage The superior tibio-
fibular joint receives an arterial supply from the anterior and posterior Patellar ligament sheath and patellar ligament The patellar
tibial recurrent branches of the anterior tibial artery. Lymphatics follow ligament is a continuation of the tendon of quadriceps femoris and
the arteries and drain to the popliteal nodes. therefore is inaccurately named. It continues from the patella to the
tibial tuberosity (see Figs 80.28, 80.31). It is strong, flat and 6–8 cm in
Innervation The superior tibiofibular joint is innervated by branches length. Proximally, it is attached to the apex of the patella and adjoining
from the common fibular nerve and from the nerve to popliteus. margins, to roughened areas on the anterior surface and to a depression
on the distal posterior patellar surface. Distally, it is attached to the


Factors maintaining stability Stability of the superior tibiofibular superior smooth area of the tibial tuberosity. This attachment is oblique,
joint is maintained by the fibrous capsule and the anterior and posterior and is more distal laterally. Its superficial fibres are continuous over the
ligaments, assisted by the biceps femoris tendon and the interosseous patella with the tendon of quadriceps femoris, the medial and lateral
membrane of the leg. parts of which descend, flanking the patella, to the sides of the tibial
tuberosity, where they merge with the fibrous capsule as the medial and
Movements Very little movement other than limited gliding takes lateral patellar retinacula. The patellar ligament is separated from the
place at the superior tibiofibular joint. Some movement must occur in synovial membrane by a large infrapatellar fat pad and from the tibia
conjunction with movement at the inferior tibiofibular joint; however, by a bursa, and lies within its own well-defined sheath.
surgical fusion (arthrodesis) of the superior tibiofibular joint seems to In the procedure of tibial osteotomy, the tibia is cut transversely just
have no effect on movements of the ankle joint. above the insertion of the patellar ligament. Failure to appreciate the
obliquity of the tibial attachment of the tendon may lead to inadvertent
Relations The common fibular nerve runs posterior to the head of division of the tendon during this procedure. The middle third of the
the fibula, medial to the tendon of biceps femoris, which is closely patellar ligament may be harvested for surgical repair of a cruciate
associated with the anterior capsule. The anterior and posterior tibial ligament.
branches of the popliteal artery, and the fibular artery are all vulnerable All other aspects of the patellofemoral joint are described with the
inferomedial to the joint. tibiofemoral joint.
PATELLOFEMORAL JOINT TIBIOFEMORAL JOINT
The patellofemoral joint is a synovial joint and is part of the knee joint. The tibiofemoral joint is a complex synovial joint and is part of the
knee joint.
Articulating surfaces The articular surface of the patella is adapted


to that of the femur. The latter extends on to the anterior surfaces of Articulating surfaces
both femoral condyles like an inverted U. Since the whole area is Proximal tibial surface
concave transversely and convex in the sagittal plane, it is an asymmetri- The proximal tibial surface (unofficially referred to as the tibial plateau)
cal sellar surface. The ‘odd’ facet on the articular surface of the patella slopes posteriorly and downwards relative to the long axis of the shaft
contacts the anterolateral aspect of the medial femoral condyle in full (Fig. 82.7). The tilt, which is maximal at birth, decreases with age, and


Joints
1387
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ReTPAHC
Transverse
1 ligament Anterior cruciate
ligament
5
2 Lateral
6 meniscus Medial
meniscus
7
Posterior
meniscofemoral
8 ligament Posterior cruciate
3
ligament
4
9
Fig. 82.8 The superior aspect of the left tibia, showing the menisci and
the attachments of the cruciate ligaments. (With permission from Drake
10
RL, Vogl AW, Mitchell A, et al (eds), Gray’s Atlas of Anatomy, Elsevier,
Churchill Livingstone. Copyright 2008.)
Fig. 82.7 The left tibial plateau. Key: 1, tibial tuberosity; 2, attachment of
anterior horn, lateral meniscus; 3, lateral condyle; 4, attachment of
posterior horn, lateral meniscus; 5, attachment of anterior horn, medial
meniscus; 6, attachment of anterior cruciate ligament; 7, medial condyle;
1 6
8, intercondylar eminence; 9, attachment of posterior horn, medial
meniscus; 10, attachment of posterior cruciate ligament.
is more marked in habitual squatters. The tibial plateau presents medial
and lateral articular surfaces (facets) for articulation with the corre- 2 5
sponding femoral condyles. The posterior surface, distal to the articular
margin, displays a horizontal, rough groove to which the capsule and 4
posterior part of the tibial collateral ligament are attached. The antero- 3
medial surface of the medial tibial condyle is a rough strip, separated
from the medial surface of the tibial shaft by an inconspicuous ridge.
The medial patellar retinaculum is attached to the medial tibial condyle
along its anterior and medial surfaces, which are marked by vascular
foramina. Fig. 82.9 Left knee joint, T1-weighted coronal magnetic resonance image
The medial articular surface is oval (long axis anteroposterior) and (MRI). Key: 1, posterior cruciate ligament; 2, tibial collateral ligament;
3, medial meniscus; 4, lateral meniscus; 5, fibular collateral ligament;
longer than the lateral articular surface. Around its anterior, medial and


6, anterior cruciate ligament.
posterior margins, it is related to the medial meniscus; the meniscal
imprint, wider posteriorly and narrower anteromedially, is often dis-
cernible. The surface is flat in its posterior half and the anterior half A depression behind the base of the medial intercondylar tubercle is
slopes superiorly about 10°. The meniscus covers much of the posterior for the attachment of the posterior horn of the medial meniscus. The
surface so that, overall, a concave surface is presented to the medial rest of the area is smooth and provides attachment for the posterior
femoral condyle. Its lateral margin is raised as it reaches the intercondy- cruciate ligament, spreading back to a ridge to which the capsule is
lar region. attached.
The lateral tibial condyle overhangs the shaft of the tibia postero- In a study of Nigerian children, the mean intercondylar distance was
laterally above a small circular facet for articulation with the fibula. The 0.2 cm at 1 year of age and there was no significant increase in this
lateral articular surface is more circular and coapted to its meniscus. In distance by the age of 10 years (Omololu et al 2003).
the sagittal plane, the articular surface is fairly flat centrally, and ant-
eriorly and posteriorly the surface slopes inferiorly. Overall, this creates Femoral surface
a rather convex surface so that, with the lateral femoral condyle in The femoral condyles, bearing articular cartilage, are almost wholly
contact, there are anterior and posterior recesses (triangular in section), convex. Opinions as to the contours of their sagittal profiles tend to
which are occupied by the anterior and posterior meniscal ‘horns’. vary. One view is that they are spiral with a curvature increasing pos-
Elsewhere, the surface has a raised medial margin that spreads to the teriorly (‘a closing helix’), that of the lateral condyle being greater. An
lateral intercondylar tubercle. Its articular margins are sharp, except alternative view is that the articular surface for contact with the tibia on
posterolaterally, where the edge is rounded and smooth: here the the medial femoral condyle describes the arcs of two circles. According


tendon of popliteus is in contact with bone. to this view, the anterior arc makes contact with the tibia near extension
and is part of a virtual circle of larger radius than the more posterior
Intercondylar area arc, which makes contact during flexion. The lateral femoral condyle is
The rough-surfaced area between the condylar articular surfaces is nar- believed to describe a single arc and thus to possess a single radius of
rowest centrally where there is an intercondylar eminence, the edges of curvature.
which project slightly proximally as the lateral and medial intercon- Tibiofemoral congruence is improved by the menisci, which are
dylar tubercles. The intercondylar area widens behind and in front of shaped to produce concavity of the surfaces presented to the femur; the
the eminence as the articular surfaces diverge (see Fig. 82.7; Fig. 82.8). combined lateral tibiomeniscal surface is deeper. The lateral femoral
The anterior intercondylar area is widest anteriorly. Anteromedially, condyle has a faint groove anteriorly, which rests on the peripheral edge
anterior to the medial articular surface, a depression marks the site of of the lateral meniscus in full extension. A similar groove appears on
attachment of the anterior horn of the medial meniscus. Behind this, a the medial condyle but does not reach its lateral border, where a narrow
smooth area receives the anterior cruciate ligament. The anterior horn strip contacts the medial patellar articular surface in full flexion. These
of the lateral meniscus is attached anterior to the intercondylar emi- grooves demarcate the femoral patellar and condylar surfaces. The dif-
nence, lateral to the anterior cruciate ligament. The eminence, with ferences between the shapes of the articulating surfaces correlate with
medial and lateral tubercles, is the narrow central part of the area. The the movements of the knee joint.
raised tubercles are thought to provide a slight stabilizing influence on
the femur. It is believed that the eminence becomes prominent once Menisci
walking commences and that the tibial condyles transmit the weight of The menisci (semilunar cartilages) are crescentic, intracapsular, fibro-


the body through the tibia. cartilaginous laminae (see Fig. 82.8; Fig. 82.9). They serve to widen,
The posterior horn of the lateral meniscus is attached to the posterior deepen and prepare the tibial articular surfaces that receive the femoral
slope of the intercondylar area. The posterior intercondylar area inclines condyles. Their peripheral attached borders are thick and convex, and
down and backwards behind the posterior horn of the lateral meniscus. their free, inner borders are thin and concave. Their peripheries are


Knee
1388
9
nOITCeS
vascularized by capillary loops from the fibrous capsule and synovial Watanabe et al (1979). In its mildest form, the partial discoid meniscus
membrane, while their inner regions are less vascular. Tears of the is simply a wider form of the normal lateral meniscus. The acute, medial
menisci are common. Peripheral tears (e.g. in the vascularized zone) free edge is interposed between the femoral and tibial condyles but it
have the potential to heal satisfactorily, especially with surgical inter- does not completely cover the tibial plateau. A complete discoid menis-
vention. Tears in the less vascular or inner zones seldom heal spontane- cus appears as a biconcave disc with a rolled medial edge and covers
ously; if surgery is indicated, these menisci are often resected. The the lateral tibial plateau. The Wrisberg type of meniscus has the same
meniscal horns are richly innervated compared with the remainder of shape as a complete discoid meniscus but its only peripheral posterior
the meniscus. The central one-third is devoid of innervation (Gronblad attachment is by the meniscofemoral ligaments. In this case, the normal
et al 1985). The proximal surfaces are smooth and concave, and in tibial attachment of the posterior horn of the lateral meniscus is lacking
contact with the articular cartilage on the femoral condyles. The distal but the posterior meniscofemoral ligament persists. As a result, this type
surfaces are smooth and flat, resting on the tibial articular cartilage. of meniscus is attached anteriorly to the tibia and posteriorly to the
Each covers approximately two-thirds of its tibial articular surface. femur, which renders the posterior horn unstable. Under these circum-
Canal-like structures open on to the surface of the menisci in infants stances, the meniscus is liable to become caught between the femur and
and young children, and may transport nutrients to deeper, less tibia: this accounts for the classic presenting symptom of the ‘clunking
vascular areas. knee’ in some patients. The aetiology of discoid meniscus is not clear.
Two structurally different regions of the menisci have been identi- Most are asymptomatic and are often found by chance at arthroscopy.


fied. The inner two-thirds of each meniscus consist of radially organized However, they may cause difficulty in gaining access to the lateral com-
collagen bundles, and the peripheral one-third consists of larger circum- partment at arthroscopy. A discoid medial meniscus is extremely rare.
ferentially arranged bundles (Ghadially et al 1983). Thinner collagen
bundles parallel to the surface line the articular surfaces of the inner Transverse ligament of the knee
part, while the outer portion is covered by synovium. This structural The transverse ligament of the knee connects the anterior convex margin
arrangement suggests specific biomechanical functions for the two of the lateral meniscus to the anterior horn of the medial meniscus (see
regions: the inner portion of the meniscus is suited to resisting compres- Fig. 82.8). It varies in thickness and is often absent. Its exact role is
sive forces while the periphery is capable of resisting tensional forces. conjectural, although one study found that the ligament was slightly
With ageing and degeneration, compositional changes occur within the taut in knee extension (Tubbs et al 2008); presumably, it helps to
menisci, which reduce their ability to resist tensional forces. Outward decrease tension generated in the longitudinal circumferential fibres of
displacement of the menisci by the femoral condyles is resisted by firm the menisci when the knee is subjected to load. A posterior menisco-
anchorage of the peripheral circumferential fibres to the intercondylar meniscal ligament is sometimes present.
bone at the meniscal horns.
The menisci spread load by increasing the congruity of the articul- Meniscofemoral ligaments
ation, provide stability by their physical presence and proprioceptive The two meniscofemoral ligaments connect the posterior horn of the
feedback, and may cushion the underlying bone from the considerable lateral meniscus to the inner (lateral) aspect of the medial femoral
forces generated during extremes of flexion and extension of the knee. condyle (Figs 82.10–82.11). The anterior meniscofemoral ligament
(ligament of Humphrey) passes anterior to the posterior cruciate liga-
Medial meniscus ment. The posterior meniscofemoral ligament (ligament of Wrisberg)


The medial meniscus is broader posteriorly and is almost a semicircle passes behind the posterior cruciate ligament and attaches proximal to
in shape (see Fig. 82.8). It is attached by its anterior horn to the anterior the margin of attachment of the posterior cruciate.
tibial intercondylar area in front of the anterior cruciate ligament; the
posterior fibres of the anterior horn are continuous with the transverse
ligament of the knee (when present). The anterior horn is in the floor
of a depression medial to the upper part of the patellar ligament. The
posterior horn is fixed to the posterior tibial intercondylar area, between
1
the attachments of the lateral meniscus and posterior cruciate ligament.
Its peripheral border is attached to the fibrous capsule and the deep
2
surface of the tibial collateral ligament. The tibial attachment of the
meniscus is known as the ‘coronary or meniscotibial ligament’. Col-
lectively, these attachments ensure that the medial meniscus is relatively
3
fixed and moves much less than the lateral meniscus.
6
4
Lateral meniscus
The lateral meniscus forms approximately four-fifths of a circle and
covers a larger area than the medial meniscus (see Fig. 82.8). Its breadth, 5
except at its short tapered horns, is more or less uniform. It is grooved
posterolat erally by the tendon of popliteus, which separates it from the
fibular collateral ligament. Its anterior horn is attached in front of the A
intercondylar eminence, posterolateral to the anterior cruciate ligament,
with which it partly blends. Its posterior horn is attached behind this
eminence, in front of the posterior horn of the medial meniscus. Its
anterior attachment is contorted so that the free margin faces postero-
superiorly, and the anterior horn rests on the anterior slope of the
lateral intercondylar tubercle. Near its posterior attachment, it com-
monly sends a posterior meniscofemoral ligament superomedially
behind the posterior cruciate ligament to the medial femoral condyle.
An anterior meniscofemoral ligament may also connect the posterior
1
horn to the medial femoral condyle anterior to the posterior cruciate
ligament. The meniscofemoral ligaments are often the sole attachments 4


of the posterior horn of the lateral meniscus. More laterally, part of the 2
tendon of popliteus is attached to the lateral meniscus, and so mobility 3
of its posterior horn may be controlled by the meniscofemoral liga-
ments and by popliteus. A meniscofibular ligament occurs in most knee
joints. As with the medial meniscus, there is a tibial attachment via the
so-called coronary ligament, but the meniscus has no peripheral bony B
attachment in the region of popliteus; in the surgical literature, this gap
is referred to as the popliteus hiatus. Fig. 82.10 A, The anterior cruciate ligament, proton density (PD)-weighted
sagittal MRI. Key: 1, suprapatellar bursa; 2, patella; 3, infrapatellar fat
Discoid lateral meniscus A discoid lateral meniscus occasionally pad; 4, femoral articular cartilage; 5, patellar ligament; 6, anterior cruciate
occurs, often bilaterally. The distinguishing features of a discoid lateral ligament. B, Anterior cruciate ligament: T2-weighted sagittal MRI. Key:
meniscus are its shape and posterior ligamentous attachments. The 1, femoral articular cartilage; 2, infrapatellar fat pad; 3, patellar ligament;
following classification of the abnormality is based on the work of 4, anterior cruciate ligament.


Joints
1389
28
ReTPAHC
A
Femur
6
1
Tendon of
adductor magnus
Plantaris
Gastrocnemius,
2 lateral head Gastrocnemius,
5
Fibular collateral medial head
ligament
Oblique popliteal
3 Arcuate popliteal ligament
ligament
Tibial collateral
Tendon of ligament
biceps femoris
Tendon of
semimembranosus
A 4 Popliteus
1
2 Popliteus
3 Fibula
Tibia
4
B
5 Tendon of
adductor magnus
8 Tendon of gastrocnemius, Tendon of
6 lateral head gastrocnemius,
medial head
Anterior cruciate
7 Femur,
ligament
B medial condyle
Femur, lateral Posterior
Fig. 82.11 A, Posterior cruciate ligament, PD-weighted sagittal MRI. condyle meniscofemoral
Key: 1, epiphyseal line; 2, femoral articular cartilage; 3, patellar ligament; Tendon of ligament
4, popliteus; 5, posterior cruciate ligament; 6, gastrocnemius. B, Medial popliteus Tibial
collateral ligament
meniscus, PD-weighted sagittal MRI. Key: 1, suprapatellar fat pad; Lateral
2, tendon of quadriceps femoris; 3, patellar articular cartilage; 4, patella; meniscus Tendon of
5, femoral articular cartilage; 6, patellar ligament; 7, infrapatellar fat pad; Fibular collateral semimembranosus
8, medial meniscus. ligament Oblique popliteal
Tibia, lateral ligament
condyle Posterior cruciate
ligament
Anatomical studies found that at least one meniscofemoral ligament Posterior ligament of
fibular head Popliteus, aponeurosis
was almost always present in the cadaveric knees examined, while both
sometimes coexisted (Gupte et al 2003). Biomechanical studies have Fibula, head Popliteus
revealed the cross-sectional area and strength of the meniscofemoral Fig. 82.12 A posterior dissection of the knee. A, Capsule intact.


ligaments to be comparable to those of the posterior fibre bundle of B, Capsule removed. (With permission from Waschke J, Paulsen F (eds),
the posterior cruciate ligament. Sobotta Atlas of Human Anatomy, 15th ed, Elsevier, Urban & Fischer.
The meniscofemoral ligaments are believed to act as secondary Copyright 2013.)
restraints, supporting the posterior cruciate ligament in minimizing
displacement caused by posteriorly directed forces on the tibia. These
ligaments are also involved in controlling the motion of the lateral
meniscus in conjunction with the tendon of popliteus during knee Medial soft tissues
flexion. The medial soft tissues (see Fig. 80.28; Fig. 82.12) are arranged in three
layers (Warren and Marshall 1979).
Soft tissues
Layer 1 Layer 1 is the most superficial and is the deep fascia that
Recent advances in imaging and surgery of knee ligaments have con- invests sartorius. The saphenous nerve and its infrapatellar branch are
tributed to an improved understanding of the anatomy of the medial superficial to the deep fascia of the leg. Sartorius inserts into the fascia
and lateral soft tissues of the knee. as an expansion rather than as a distinct tendon. The fascia spreads
inferiorly and anteriorly to lie superficial to the distinct and readily
Capsule and retinacula
identifiable tendons of gracilis and semitendinosus and their insertions.
The joint capsule is a fibrous membrane of variable thickness. Anterior ly, The latter two tendons are commonly harvested for surgical reconstruc-
it is replaced by the patellar ligament and does not pass proximal to tion of damaged cruciate ligaments. To gain access to them, the upper
the patella or over the patellar area. Elsewhere, it lies deep to expansions edge of sartorius can be identified. The sartorius (layer 1) fascia is then
from vasti medialis and lateralis, separated from them by a plane of incised to reveal the tendons. Deep to the tendons is the anserine bursa,
vascularized loose connective tissue. The expansions are attached to the which overlies the superficial part of the tibial collateral ligament; this
patellar margins and patellar ligament, extending back to the corre- bursa sometimes becomes inflamed, especially in track and field ath-


sponding collateral (tibial and fibular) ligaments and distally to the letes. Posteriorly, layer 1 overlies the tendons of gastrocnemius and the
tibial condyles. They form medial and lateral patellar retinacula, the structures of the popliteal fossa. Anteriorly, layer 1 blends with the
lateral being reinforced by the iliotibial tract. anterior limit of layer 2 and the medial patellar retinaculum. More
Posteriorly, the capsule contains vertical fibres that arise from the inferiorly, layer 1 blends with the periosteum.
articular margins of the femoral condyles and intercondylar fossa, and A condensation of tissue passes from the medial border of the
from the proximal tibia. The fibres mainly pass downwards and some- patella to the medial epicondyle of the femur (the medial patellofemo-
what medially. The oblique popliteal ligament is a well-defined thicken- ral ligament), the anterior horn of the medial meniscus (the menisco-
ing across the posteromedial aspect of the capsule, and is one of the patellar ligament), and the medial tibial condyle (the patellotibial
major extensions from the tendon of semimembranosus. ligament).


Knee
1390
9
nOITCeS
Layer 2 Layer 2 is the plane of the superficial part of the tibial col- patella. The latter is thicker and subdivided into three parts: the lateral
lateral ligament, which means that the tendons of gracilis and semi- patellofemoral ligament, running from the lateral patellar border to the
tendinosus lie between layers 1 and 2. The superficial part of the tibial lateral epicondyle of the femur; the transverse retinaculum, running
collateral ligament has vertical and oblique portions. The former con- from the iliotibial tract to the mid-patella; and the patellotibial band,
tains vertically orientated fibres that pass from the medial epicondyle running from the patella to the lateral tibial condyle.
of the femur to a large insertion on the medial surface of the proximal The fascia lata and the iliotibial tract lie posterior to the lateral reti-
end of the tibial shaft. It extends to an area about 5 cm distal to the naculum. They come together distally to insert on to the tibia at a
joint line. Its anterior edge is rolled and easily seen just posterior to the tubercle (Gerdy’s tubercle) on the anterolateral proximal tibia; some
insertions of gracilis and semitendinosus once layer 1 has been opened. fibres continue to insert on the tibial tuberosity. Proximally, the fascia
The posteriorly placed oblique fibres run posteroinferiorly from the lata merges with the lateral intermuscular septum. Posteriorly, it blends
medial epicondyle of the femur to blend with the underlying layer 3 with the fascia over biceps femoris. Here, as it emerges from behind the
(capsule), effectively to insert on the posteromedial tibial articular biceps femoris tendon, the common fibular nerve lies in a thin layer of
margin and posterior horn of the medial meniscus. This area is re- fat bound by the fascia.
inforced by a part of the insertion of semimembranosus. There is a The fibular collateral ligament arises from the lateral epicondyle of


vertical split in layer 2 anterior to the superficial part of the tibial col- the femur posterior to the popliteus insertion and just proximal to the
lateral ligament. The fibres anterior to the split pass superiorly to blend groove for popliteus. It is a cord-like structure that passes distally, super-
with vastus medialis fascia and layer 1 in the medial patellar retinacu- ficial to the popliteus tendon and deep to the lateral retinaculum, to
lum. The fibres posterior to the split pass superiorly to the medial epi- attach to the fibular head, where it blends with the biceps femoris
condyle and thence anteriorly as the medial patellofemoral ligament. tendon just anterior to the apex of the head of the fibula. It is separated
from the capsule by a thin layer of fat and the inferior lateral genicular
Layer 3 Layer 3 is the capsule of the knee joint and can be separated vessels.
from layer 2 everywhere except anteriorly close to the patella, where it The single most important stabilizer of the posterolateral knee is the
blends with the more superficial layers. Deep to the superficial part of popliteofibular (short external lateral) ligament. It passes from the
the tibial collateral ligament it is thick and has vertically orientated popliteus tendon at a level just below the joint line, posteriorly, laterally
fibres that make up the deep medial part of the tibial collateral liga- and inferiorly, to the apex of the head of the fibula. As a passive ‘tether’
ment. It sends fibres to the medial meniscus. Anteriorly, the separation combined with the popliteus tendon proximal to it, it resists lateral
of the superficial and deep parts of the tibial collateral ligament is rotation of the tibia. Its connection to the tendon of popliteus also
distinct. Posteriorly, layers 2 and 3 blend to form a conjoined postero- allows ‘dynamic’ tensioning.
medial capsule. The fabellofibular ligament is a condensation of fibres that runs
either from the fabella (a sesamoid bone sometimes found within the
Lateral soft tissues
tendon of the lateral head of gastrocnemius) or from the lateral head


The lateral soft tissues (see Fig. 82.12; Fig. 82.13) are also arranged in of gastrocnemius (if the fabella is absent), to the apex of the head of
three layers (Seebacher et al 1982), which collectively have been referred the fibula. The arcuate ligament is a condensation of fibres that runs
to as the lateral collateral ligamentous complex (Nissman et al 2008). from the apex of the head of the fibula, posteromedially over the emerg-
The most superficial layer is the lateral patellar retinaculum. The middle ing tendon of popliteus below the level of the tibial joint surface, to the
layer consists of the fibular collateral popliteofibular, fabellofibular and tibial intercondylar area. The lateral joint capsule is thin and blends
arcuate ligaments. The recently described anterolateral ligament of the posteriorly with the arcuate ligament. Anteriorly, it forms the weak, lax
knee may exist in this layer (Claes et al 2013). The deep layer is the coronary or meniscotibial ligament, which attaches the inferior border
lateral part of the capsule. of the meniscus to the lateral tibia.
The lateral patellar retinaculum consists of superficial oblique and
deep transverse portions. The former runs from the iliotibial tract to the Ligaments
Cruciate ligaments
The cruciate ligaments, so named because they cross each other, are very
strong, richly innervated intracapsular structures. The point of crossing
Suprapatellar bursa
is located a little posterior to the articular centre. They are named ant-
Tendon of erior and posterior with reference to their tibial attachments (Figs
quadriceps femoris 82.14–82.15; see Fig. 82.17). A synovial membrane almost surrounds
the ligaments but is reflected posteriorly from the posterior cruciate
ligament to adjoining parts of the capsule; the intercondylar part of the
posterior region of the fibrous capsule therefore has no synovial
Subfascial
prepatellar bursa covering.
A B
Patellar ligament
Fibular collateral ligament Intercondylar region
Lateral meniscus Anterior cruciate
Tendon of popliteus
ligament


Deep infrapatellar bursa
Arcuate popliteal ligament Posterior cruciate
ligament
Tendon of biceps femoris Medial meniscus
Lateral meniscus
Fig. 82.13 The left knee joint, lateral aspect. The synovial cavity is Fig. 82.14 The left knee joint. A, Anterior aspect in full flexion.
distended and the synovial membrane appears grey. (With permission B, Posterior aspect in extension. (With permission from Drake RL, Vogl
from Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, AW, Mitchell A, et al (eds), Gray’s Atlas of Anatomy, Elsevier, Churchill
15th ed, Elsevier, Urban & Fischer. Copyright 2013.) Livingstone. Copyright 2008.)


Joints
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ReTPAHC
Medial femoral condyle Fig. 82.15 The
intercondylar notch at Tendon of quadriceps
arthroscopy, showing femoris
the anterior cruciate
and transverse
Suprapatellar bursa
ligaments of the knee.
(Courtesy of Smith and
Nephew Endoscopy.)
Subcutaneous Fibrous capsule
prepatellar bursa
Infrapatellar pad of fat, Anterior
extending into cruciate ligament
infrapatellar fold
Patellar ligament Posterior
cruciate ligament
Transverse Anterior cruciate Deep infrapatellar bursa
ligament ligament
Anterior cruciate ligament The anterior cruciate ligament is
Fig. 82.16 A sagittal section through the left knee joint, lateral aspect.
attached to the anterior intercondylar area of the tibia, just anterior and
slightly lateral to the medial intercondylar tubercle, partly blending
with the anterior horn of the lateral meniscus (see Fig. 82.8). It ascends
posterolaterally, twisting on itself and fanning out to attach high on the
posteromedial aspect of the lateral femoral condyle (Girgis et al 1975).
The average length and width of an adult anterior cruciate ligament are
38 mm and 11 mm, respectively. It is formed of two, or possibly three,
Femur
functional bundles that are not apparent to the naked eye but can be
demonstrated by microdissection techniques. The bundles are named Articular capsule
anteromedial, intermediate and posterolateral, according to their tibial Posterior cruciate
attachments (Amis and Dawkins 1991). ligament
Posterior cruciate ligament The posterior cruciate ligament is Ligamentum
mucosum
thicker and stronger than the anterior cruciate ligament (see Fig. 82.8), overlying
the average length and width of an adult posterior cruciate ligament anterior
being 38 mm and 13 mm, respectively. It is attached to the lateral cruciate ligament
surface of the medial femoral condyle and extends up on to the anterior
Alar folds overlying
part of the roof of the intercondylar fossa, where its attachment is the infrapatellar fat pad
extensive in the anteroposterior direction. Its fibres are adjacent to the


articular surface. They pass distally and posteriorly to a fairly compact
attachment posteriorly in the intercondylar region and in a depression
on the adjacent posterior tibia. This gives a fan-like structure in which
fibre orientation is variable. Anterolateral and posteromedial bundles
Patella
have been defined; they are named (against convention) according to
their femoral attachments. The anterolateral bundle tightens in flexion
while the posteromedial bundle is tight in extension of the knee. Each
Tendon of quadriceps
bundle slackens as the other tightens. Unlike the anterior cruciate liga- femoris
ment, it is not isometric during knee motion, i.e. the distance between
attachments varies with knee position. The posterior cruciate ligament
ruptures less commonly than the anterior cruciate ligament and rupture
Fig. 82.17 The left knee joint in full flexion. The tendon of quadriceps
is usually better tolerated by patients than rupture of the anterior cruci-
femoris has been sectioned and the patella retracted distally. Compare
ate ligament.
with Figure 82.14A.
Synovial membrane, plicae and fat pads
it can be thickened and inflamed, usually following acute or chronic
The synovial membrane of the knee is the most extensive and complex trauma.
in the body. It forms a large suprapatellar bursa between quadriceps The suprapatellar plicae are remnants of an embryonic septum that
femoris and the lower femoral shaft proximal to the superior patellar completely separates the suprapatellar bursa from the knee joint. Occa-
border (Fig. 82.16). The bursa is an extension of the joint cavity. The sionally, a septum persists, either in its entirety or perforated by a small
attachment of articularis genus to its proximal aspect prevents the bursa peripheral opening.
from collapsing into the joint. Alongside the patella, the membrane The infrapatellar fat pad is the largest part of a circumferential extra-
extends beneath the aponeuroses of the vasti, especially under vastus synovial fatty ring that extends around the patellar margins (Newell
medialis. It extends proximally a hand’s breadth above the superior pole 1991).


of the patella. Distal to the patella, the synovial membrane is separated At the sides of the joint, the synovial membrane descends from the
from the patellar ligament by an infrapatellar fat pad. Where it lies femur and lines the capsule as far as the menisci, whose surfaces have
beneath the fat pad, the membrane projects into the joint as two fringes, no synovial covering. Posterior to the lateral meniscus, the membrane
alar folds, which bear villi. The folds converge posteriorly to form a forms a subpopliteal recess between a groove on the meniscal surface
single infrapatellar fold or plica (ligamentum mucosum), which curves and the tendon of popliteus, which may connect with the superior
posteriorly to its attachment in the femoral intercondylar fossa (Fig. tibiofibular joint. The relationship of the synovial membrane to the
82.17). This fold may be a vestige of the inferior boundary of an origi- cruciate ligaments is described above.
nally separate femoropatellar joint. The extent of the infrapatellar plica
ranges from a thin cord to a complete sheet that can obstruct the Bursae
passage of instruments during knee arthroscopy. When substantial, it Numerous bursae are associated with the knee. Anteriorly, there is a
has been mistaken for the anterior cruciate ligament, which is directly large subcutaneous prepatellar bursa between the lower half of the
posterior to it. The medial plica extends in the midline anteriorly from patella and skin; a small, deep infrapatellar bursa between the tibia and
the medial alar fold medially to the suprapatellar bursa. Occasionally, patellar ligament; a subcutaneous infrapatellar bursa between the distal