Medial collateral ligament The medial collateral ligament ( MCL or tibial collateral ligament ) is one of the four major ligament s of the knee . It is on the medial ( inner ) side of the knee joint in humans and other primates . Structure . 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 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 . 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 . Embryologically and phylogenically , the ligament represents the distal portion of the tendon of adductor magnus muscle . In lower animals , adductor magnus inserts into the tibia . Because of this , the ligament occasionally contains muscle fibres . This is an atavistic variation . Causes of injury . 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 . It may be difficult to apply pressure on the injured leg for at least a few days . Skiing . The most common knee structure damaged in skiing is the medial collateral ligament , although the carve turn has diminished the incidence somewhat . American football . MCL strains and tears are fairly common in American football . The center and the guards are the most common victims of this type of injury due to the grip trend on their cleats , although sometimes it can be caused by a helmet striking the knee . The number of football players who get this injury has increased in recent years . Companies are currently trying to develop better cleats that will prevent the injury . Treatment . Depending on the grade of the injury , the lowest grade ( grade 1 ) can take between 2 and 10 weeks for the injury to fully heal . Recovery times for grades 2 and 3 can take weeks to several months . Treatment of a partial tear or stretch injury is usually conservative . Physical Therapy should be a first choice option for treatment and diagnosis 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 . Since 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 . Other non - surgical approaches for more severe MCL injuries may include prolotherapy , which has been shown by Reeves in a small RCT to reduce translation on KT - 1000 arthrometer versus placebo . The future of non - surgical care for a non - healing MCL injury with laxity ( partial ligament tear ) is likely bioengineering . Fan et al . ( 2008 ) have demonstrated that knee ligament reconstruction is possible using mesenchymal stem cells and a silk scaffold .