The medial collateral ligament (MCL) is one of the knee’s four major ligaments, located on the medial aspect of the knee joint. It is also known as the tibial collateral ligament.


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


The fibers of the posterior part of the MCL 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 cm long, which inclines forward as it descends. It is inserted into the medial surface of the body of the tibia about 2.5 cm below the level of the condyle. Crossing on top of the lower part of the MCL is the pes anseinus, 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.


The MCL resists forces that would push the knee medially, which would otherwise produce valgus deformity.

Diability if injured

An MCL injury can be very painful and is caused by a valgus stress to a slightly bent knee, often when landing, bending, or on high impact. Depending on the grade of the injury, the lowest grade (grade I) can take between 2 and 10 weeks for the injury to fully heal. Recovery times for grades 2 and 3 are difficult to predict because of the amount of damage done can take weeks to several months. It is difficult to apply pressure on the injured leg for at least a few days.


Treatment of a partial tear or stretch injury is usually conservative. Physical therapy should be the first choice for treatment of injuries to this structure. This includes measures to control inflammation as well as bracing. Kannus has shown good clinical results with conservative care of grade II sprains, but poor results in grade III sprains. As a result, more severe grade III and IV injuries to the MCL that lead to ongoing instability may require arthroscopic surgery. However, the medical literature considers surgery for most MCL injuries to be controversial. Because isolated MCL injuries are uncommon, surgery is often focused on ACL replacement or repair with combined surgical approaches being common. For higher-grade tears of the MCL with ongoing instability, the MCL can be sutured or replaced.


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