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Meniscal Tears / Tears of the Knee Cartilages
Definition: A partial or complete discontinuity of fibrocartilagenous matrix comprising one or more of the knee menisci.
Causes: The medial meniscus is more commonly damaged than its lateral counterpart due to it's firmer fixation about the tibial plateau via the coronary ligaments. Menisci are most often torn during a rotation movement with either the tibia or the femur maintained in a fixed position. An example would be that of skier turning their thigh one way and the ski on that same limb not permitting the leg to follow in the direction of the thigh, with resulting torque tearing the meniscus. Other causes of meniscal tears are the result of cartilaginous degeneration and usually occur in older adults (osteoarthrosis).
Examination: Patients suffering from a torn meniscus may present as asymptomatic or in considerable pain, usually over the joint line of the knee. An acute injury can be associated with oedema of the knee joint, and potentially ecchymoses if any of the ligaments (coronary, cruciate) or joint capsule of the knee have been damaged. The patient may also complain of "clicking" within the knee and may not the able to fully lock or extend the knee. The frayed meniscus may because trapped between the tibial plateau and femoral condyles during certain movements, leading to a catching sensation inside the knee. It is worth noting that a tear of the medial meniscus can occur as part of what is referred to as: 'the unhappy triad': a damaged anterior cruciate, and medial collateral ligament.
Orthopaedic test for meniscal tears of the knee:
Palpation of the joint line will usually elicit pain if a meniscus is torn.
McMurray test: with the patient supine, the examiner flexes the patient's thigh and knee to 90º while palpating the knee joint. The practitioner than introduces a valgus force at the knee if a medial meniscal tear is suspected or a varus force if a lateral meniscal tear is suspected, after which the examiner extends the hip and knee, looking out for an audible/palpable click within the tested knee indicating a positive, this may be associated with pain.