The medial collateral ligament of the knee is the primary medial stabiliser, resisting the valgus forces of contact sport and daily activities. It has a superficial layer (the primary valgus stabiliser) and a deep layer attached to the medial meniscus — making medial meniscus tears more common with MCL injuries because the deep MCL tethers the meniscus and tears it when the ligament is stressed. MCL injuries are the most common knee ligament injuries and the majority heal without surgery.
| Origin | Medial femoral epicondyle |
|---|---|
| Insertion | Medial tibial shaft below the pes anserinus insertion (4 to 5 cm below the joint line) |
| Actions | Primary restraint against valgus stress at the knee; also resists external tibial rotation and anterior tibial translation |
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MCL injuries are graded I (sprain, intact), II (partial tear with maintained end point), and III (complete tear with soft end point on valgus stress). Isolated Grade III MCL injuries are treated non-operatively with functional bracing because the remaining medial structures allow reliable healing — a key distinction from ACL tears that cannot heal without surgery. MCL injuries associated with ACL or PCL tears require more careful assessment for surgical repair.
Medial knee ligament injury from valgus contact force graded I through III, with isolated Grade III tears managed non-operatively with functional bracing and surgical repair reserved for combined ligament injuries.
