Medial collateral ligament

The medial collateral ligament (MCL), also called the superficial medial collateral ligament (sMCL) or tibial collateral ligament (TCL), is one of the major ligaments of the knee. It is on the medial (inner) side of the knee joint and occurs in humans and other primates. Its primary function is to resist valgus (inward bending) forces on the knee.

It is a broad, flat, membranous band, situated slightly posterior on the medial side of the knee joint. It is attached proximally to the medial epicondyle of the femur, immediately below the adductor tubercle; below to the medial condyle of the tibia and medial surface of its body.

It resists forces that would push the knee medially, which would otherwise produce valgus deformity. It provides up to 78% of the restraining force that resists valgus (inward pressing) loads on the knee.

The fibers of the posterior part of the ligament are short and incline backward as they descend; they are inserted into the tibia above the groove for the semimembranosus muscle.

The anterior part of the ligament is a flattened band, about 10 centimeters long, which inclines forward as it descends.

It is inserted into the medial surface of the body of the tibia about 2.5 centimeters below the level of the condyle.

Crossing on top of the lower part of the MCL is the pes anserinus, the joined tendons of the sartorius, gracilis, and semitendinosus muscles; a bursa is interposed between the two.

The MCL's deep surface covers the inferior medial genicular vessels and nerve and the anterior portion of the tendon of the semimembranosus muscle, with which it is connected by a few fibers; it is intimately adherent to the medial meniscus.