meniscus tear meniscus tear a tear of a meniscus is a rupturing of one or more of the fibrocartilage strips in the knee called menisci. when doctors and patients refer to "torn cartilage" in the knee, they actually may be referring to an injury to a meniscus at the top of one of the tibiae. menisci can be torn during innocuous activities such as walking or squatting. they can also be torn by traumatic force encountered in sports or other forms of physical exertion. the traumatic action is most often a twisting movement at the knee while the leg is bent. in older adults, the meniscus can be damaged following prolonged 'wear and tear'. especially acute injuries (typically in younger, more active patients) can lead to displaced tears which can cause mechanical symptoms such as clicking, catching, or locking during motion of the joint. the joint will be in pain when in use, but when there is no load, the pain goes away. tear of meniscushead of right tibia seen from above, showing menisci and attachments of ligamentsspecialtyorthopedics a tear of the medial meniscus can occur as part of the unhappy triad, together with a tear of the anterior cruciate ligament and medial collateral ligament. signs and symptoms the common signs and symptoms of a torn meniscus are knee pain, particularly along the joint line, and swelling. these are worse when the knee bears more weight (for example, when running). another typical complaint is joint locking, when the affected person is unable to straighten the leg fully. this can be accompanied by a clicking feeling. sometimes, a meniscal tear also causes a sensation that the knee gives way. a person with a torn meniscus can sometimes remember a specific activity during which the injury was sustained. a tear of the meniscus commonly follows a trauma that involves rotation of the knee while it was slightly bent. these maneuvers also exacerbate the pain after the injury; for example, getting out of a car is often reported as painful. causes there are two menisci in the knee. they sit between the thigh bone and the shin bone. while the ends of the thigh bone and the shin bone have a thin covering of soft hyaline cartilage, the menisci are made of tough fibrocartilage and conform to the surfaces of the bones they rest on. one meniscus rests on the medial tibial plateau; this is the medial meniscus. the other meniscus rests on the lateral tibial plateau; this is the lateral meniscus. the menisci are nourished by small blood vessels but have a large area in the center with no direct blood supply (avascular). this presents a problem when there is an injury to the meniscus, as the avascular areas tend not to heal. without the essential nutrients supplied by blood vessels, healing cannot take place. the two most common causes of a meniscal tear are traumatic injury (often seen in athletes) and degenerative processes, which are the most common tear seen in all ages of patients. meniscal tears can occur in all age groups. traumatic tears are most common in active people aged 10–45. traumatic tears are usually radial or vertical in the meniscus and more likely to produce a moveable fragment that can catch in the knee and therefore require surgical treatment. a meniscus can tear due to an internally or externally rotated knee in a flexed position, with the foot in a flexed position. it is not uncommon for a meniscal tear to occur along with injuries to the anterior cruciate ligament acl and the medial collateral ligament mcl — these three problems occurring together are known as the "unhappy triad," which is seen in sports such as football when the player is hit on the outside of the knee. individuals who experience a meniscal tear usually experience pain and swelling as their primary symptoms. another common complaint is joint locking, or the inability to completely straighten the joint. this is due to a piece of the torn cartilage preventing the normal functioning of the knee joint. degenerative tears are most common in people from age 40 upward but can be found at any age, especially with obesity. degenerative meniscal tears are thought to occur as part of the aging process when the collagen fibers within the meniscus start to break down and lend less support to the structure of the meniscus. degenerative tears are usually horizontal, producing both an upper and a lower segment of the meniscus. these segments do not usually move out of place and are therefore less likely to produce mechanical symptoms of catching or locking. risk factors the meniscus is made of cartilage, a viscoelastic material, which makes it more susceptible to rate of loading injuries. repetitive loading can also lead to injury. recent studies have shown people who experience rapid rate of loading and/or repetitive loading to be the most susceptible to meniscus tears. people over the age of 60 who have working conditions in which squatting and kneeling are common are more susceptible to degenerative meniscal tears. athletes who constantly experience a high rate of loading (e.g. soccer, rugby) are also susceptible to meniscus tears. studies have also shown with increasing time between acl injury and acl reconstruction, there is an increasing chance of meniscus tears. this study showed meniscus tears occurring at a rate of 50–70% depending on how long after the acl injury the surgery occurred. meniscal ramp lesions (tears of the medial meniscus posterior horn at the menisco-capsular junction) occur in approximately 25% of acl-injured knees. lateral meniscal root tears occur in approximately 7% of acl injured knees pathophysiology the force distribution is across the knee joint, increasing force concentration on the cartilage and other joint structures. damage to the meniscus due to rotational forces directed to a flexed knee (as may occur with twisting sports) is the usual underlying mechanism of injury. a valgus force applied to a flexed knee with the foot planted and the femur rotated externally can result in a lateral meniscus tear. a varus force applied to the flexed knee when the foot is planted and the femur rotated internally result in a tear of the medial meniscus. tears produce rough surfaces inside the knee, which cause catching, locking, buckling, pain, or a combination of these symptoms. abnormal loading patterns and rough surfaces inside the knee, especially when coupled with return to sports, significantly increase the risk of developing arthritis if not already present. anatomy the menisci are c-shaped wedges of fibrocartilage located between the tibial plateau and femoral condyles. the menisci contain 70% type i collagen. the larger semilunar medial meniscus is attached more firmly than the loosely fixed, more circular lateral meniscus. the anterior and posterior horns of both menisci are secured to the tibial plateaus. anteriorly, the transverse ligament connects the 2 menisci; posteriorly, the meniscofemoral ligament helps stabilize the posterior horn of the lateral meniscus to the femoral condyle. the coronary ligaments connect the peripheral meniscal rim loosely to the tibia. although the lateral collateral ligament (lcl) passes in close proximity, the lateral meniscus has no attachment to this structure. the joint capsule attaches to the entire periphery of each meniscus but adheres more firmly to the medial meniscus. an interruption in the attachment of the joint capsule to the lateral meniscus, forming the popliteal hiatus, allows the popliteus tendon to pass through to its femoral attachment site. contraction by the popliteus during knee flexion pulls the lateral meniscus posteriorly, avoiding entrapment within the joint space. the medial meniscus does not have a direct muscular connection. the medial meniscus may shift a few millimeters, while the less stable lateral meniscus may move at least 1 cm. in 1978, shrive et al. reported that the collagen fibers of the menisci are oriented in a circumferential pattern. when a compressive force is applied in the knee joint, a tensile force is transmitted to the menisci. the femur attempts to spread the menisci anteroposteriorly in extension and mediolaterally in flexion. shrive et al. further studied the effects of a radial cut in the peripheral rim of the menisci during loading. in joints with intact menisci, the force was applied through the menisci and articular cartilage; however, a lesion in the peripheral rim disrupted the normal mechanics of the menisci and allowed it to spread when a load was applied. the load now was distributed directly to the articular cartilage. in light of these findings, it is essential to preserve the peripheral rim during partial meniscectomy to avoid irreversible disruption of the structure's hoop tension capability. diagnosis physical examination after noting symptoms, a physician can perform clinical tests to determine if the pain is caused by compression and impingement of a torn meniscus. the knee is examined for swelling. in meniscal tears, pressing on the joint line on the affected side typically produces tenderness. the mcmurray test involves pressing on the joint line while stressing the meniscus (using flexion–extension movements and varus or valgus stress). similar tests are the steinmann test (with the patient sitting) and the apley grind test (a grinding maneuver while the person lies prone and the knee is bent 90°) and the thessaly test (flexing the affected knee to 20 degrees, pivoting on the knee to see if the pain is reproduced). bending the knee (into hyperflexion if tolerable), and especially squatting, is typically a painful maneuver if the meniscus is torn. the range of motion of the joint is often restricted. cooper's sign is present in over 92% of tears. it is a subjective symptom of pain in the affected knee when turning over in bed at night. osteoarthritic pain is present with weightbearing, but the meniscal tear causes pain with a twisting motion of the knee as the meniscal fragment gets pinched, and the capsular attachment gets stretched causing the complaint of pain. radiology bucket-handle tear of the lateral meniscus (red). medial meniscus intact (green). mri, coronal t2 *-weighted gre sequence. x-ray images (normally during weightbearing) can be obtained to rule out other conditions or to see if the patient also has osteoarthritis. the menisci themselves cannot be visualised with plain radiographs. if the diagnosis is not clear from the history and examination, the menisci can be imaged with magnetic resonance imaging (an mri scan). this technique has replaced previous arthrography, which involved injecting contrast medium into the joint space. in straightforward cases, knee arthroscopy allows quick diagnosis and simultaneous treatment. recent clinical data shows that mri and clinical testing are comparable in sensitivity and specificity when looking for a meniscal tear. classification types of meniscus tears a meniscal tear can be classified in various ways, such as by anatomic location or by proximity to blood supply. various tear patterns and configurations have been described. these include: radial tears flap or parrot-beak tears peripheral, longitudinal tears bucket-handle tears horizontal cleavage tears complex, degenerative tears these tears can then be further classified by their proximity to the meniscus blood supply, namely whether they are located in the “red-red,” “red-white,” or “white-white” zones. the functional importance of these classifications, however, is to ultimately determine whether a meniscus is repairable. the repairability of a meniscus depends on a number of factors. these include: age/strength activity level tear pattern chronicity of the tear associated injuries (anterior cruciate ligament injury) healing potential prevention tear of a meniscus is a common injury in many sports. the menisci hold 30–50% of the body load in standing position. some sports where a meniscus tear is common are american football, association football, ice hockey and tennis. regardless of what the activity is, it is important to take the correct precautions to prevent a meniscus tear from happening. footwear there are three major ways of preventing a meniscus tear. the first of these is wearing the correct footwear for the sport and surface that the activity is taking place on. this means that if the sport being played is association football, cleats are an important item in reducing the risk of a meniscus tear. the proper footwear is imperative when engaging in physical activity because one off-balanced step could mean a meniscus tear. it is highly advised that cleats contain a sole that molds around the foot, no fewer than fourteen cleats per shoe, no lower than