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Medial collateral ligament injuries

Medial collateral ligament injuries
The MCL is the most commonly injured ligament in the knee. The incidence is probably higher than reported, because many minor MCL injuries are never seen by physicians. The treatment of these injuries
has changed; in the 1970s surgical treatment was common, but today most MCL injuries are treated conservatively, with early rehabilitation.

Medial knee stability is primarily given by the medial static and dynamic stabilizers extending from the midline anteriorly to the midline posteriorly of the knee. The static structures are the superficial MCL, the posterior oblique ligament, and the middle third of the capsule ligament.Dynamic stability is provided by the per anserinus tendons, especially the semimembranosus tendon.
The three units of the MCL are the superficial MCL, the deep MCL, and the posterior oblique ligament.These structures do not work independently, but as an integrated unit to resist abnormal loads.
The superficial MCL is on an average 4.4 in (11 cm) long and 0.2 in (0.5 cm) wide. It originates from the medial femoral condyle just anterior to the tubercle going distally to insert 2–3 in (5–7 cm) below the joint line on the anteromedial tibia just under the pes anserinus insertion. The anterior fibers tense throughout flexion and the posterior fibers slacken in flexion. The MCL is tight in external rotation.

The middle third of the deep MCL is a short structure—about 0.8–1.2 in (2–3 cm) long—which is attached to the meniscus underlying the MCL. The deep and superficial layers are often integrated proximally. This ligament is relatively slack to allow knee motion, but short enough to hold the meniscus firmly along its periphery. The deep portion can be ruptured both proximally and distally to the meniscal attachment regardless of the location of the tear of the superficial MCL.

The posterior oblique ligament is a thickened capsular ligament originating just posterior to the superficial MCL at the condyle inserting just below the joint line. It is attached to the posterior horn of the medial meniscus. This structure is important in maintaining medial stability.The posterior oblique ligament becomes slack in flexion.
Biomechanical studies show that the MCL’s main function is to resist valgus (outward side motion of the leg) and external rotation forces of the tibia in relation to the femur. The superficial MCL has been found to be responsible for 57% of medial stability at 5° of knee flexion and up to 78% at 25° of flexion. The deep MCL accounted for 8% at 5° and 4% at 25° and the posterior oblique accounted for 18% and 4%

Symptoms and diagnosis
– The history of injury can include noncontact valgus trauma, as well as external rotation injury in skiing.
A major MCL injury may be caused by a lateral blow to the lower thigh or upper leg in soccer or American football.
– Pain occurs at the time of injury. Absence of severe pain does not exclude a severe injury; minor injuries may be more painful than more severe injuries.
– The ability to walk can be impaired after an MCL injury: 50% of athletes with severe (grade III) injuries cannot walk unaided by external support after the injury.
– Swelling of the joint is unusual; it indicates a more severe injury in the joint itself.
– Tenderness is usually present over the site of injury. The most common location for tenderness is the medial femoral condyle.
– Testing the laxity with valgus stress tests is important .

The grading is as follows:
• grade 0—normal, i.e. no joint opening;
• grade I—0.2 in (1–4 mm) joint opening;
• grade II—0.2–0.4 in (5–10 mm) joint opening;
• grade III—0.4–0.6 in (10–15 mm) joint opening.

– Grade I and II injuries have well-defined end points, but a grade III tear occurs only with the soft, mushy end point with valgus stress testing.It should be pointed out that even with a complete medial injury,there will be no valgus instability with the knee in full extension if the posterior cruciate ligament and the posterior capsule are intact. The medial instability should be primarily tested at 30° of knee flexion but include testing in extension.
– Lachman’s test for ACL stability should be carried out when gross medial instability is present. A grade III MCL injury is associated with an ACL injury in 95% of cases.

– Correct diagnosis is the basis for successful treatment. Acute grade I and II isolated MCL injuries are all treated conservatively with quick rehabilitation.
– For grade I and II injuries, weightbearing and early motion can start as early as possible. A brace can be beneficial.

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