History
A thorough history should be obtained prior to performing the physical examination. The following questions should be answered:
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How and when did the injury occur?
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What was the mechanism of injury?
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What was the position of the knee at the time of injury?
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Was the patient able to ambulate immediately after the injury? If so, is the patient still able to ambulate?
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Did the knee swell immediately or was swelling delayed?
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Did the patient experience a sensation of a tearing or hear an audible pop?
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Did any deformity occur? (Deformity may signify a patella subluxation or dislocation.)
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Have any prior injuries or fractures occurred?
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Where is the site of injury within the MCL?
Physical Examination
A complete physical examination of the knee should be performed after a thorough history is obtained. Attention should be directed toward localizing the MCL injury and identifying any associated injuries.
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Inspection and palpation of the knee should identify the presence and location of point tenderness, localized soft tissue swelling, deformity, or ecchymosis. The region of injury within the ligament should be noted. A large joint effusion indicates an associated intra-articular injury. Outcome can be influenced by the location of the injury within the ligament.
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The integrity of the MCL is tested with a valgus stress. If any abnormal laxity is noted, the quality of the endpoint should be determined. Testing should be performed in full extension and at 30° of flexion. Grading of the injury is based on the amount of laxity. Any laxity is compared to the opposite knee.
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Rotation should be compared to the opposite knee when evaluating for associated posteromedial injuries.
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Anterior and posterior draw signs and a Lachman are performed to rule out associated injuries.
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Associated injuries include the following:
Other structures within the knee may be injured in association with the MCL. The anterior cruciate ligament (ACL) is injured in approximately 20% of grade 1 injuries and as many as 78% of grade 3 injuries.
The medial meniscus is injured 5-25% of the time; the incidence increases with severity of the MCL injury.
The extensor mechanism, including the vastus medialis obliquus and retinacular fibers, is also injured in 9-21% of the cases.
The posterior cruciate ligament (PCL) may be injured, but no incidence has been reported.
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Classification systems include the following:
American Medical Association Committee on the Medical Aspects of Sports (1966)
Grade 1 - 0-5 mm of opening
Grade 2 - 5-10 mm of opening
Grade 3 - Greater than 10 mm of opening
O'Donoghue classification
Grade 1 - Few torn fibers, structurally intact
Grade 2 - Incomplete tear, no pathologic laxity
Grade 3 - Complete tear, pathologic laxity
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The medial and lateral collateral ligaments of the knee. Courtesy of Randale Sechrest, MD, CEO, Medical Multimedia Group
