The deep MCL (deep medial collateral ligament, medial capsular ligament) is a distinct layer of the medial knee separate from the superficial MCL, composed of the meniscofemoral and meniscotibial (coronary) ligaments. The meniscotibial portion (coronary ligament) connects the medial meniscus periphery to the tibia, limiting meniscal translation; the meniscofemoral portion connects the medial meniscus to the femur. Together they form the deep layer of the medial ligamentous complex.
Resists medial compartment opening to valgus stress at full extension, limits medial meniscal posterior translation, and contributes to rotational stability in combination with the superficial MCL.
The deep MCL is disrupted in high-grade medial knee injuries, producing the characteristic medial meniscus-MCL combined injury pattern. Deep MCL tears allow the medial meniscus to translate further posteriorly than normal, contributing to medial meniscal pathology in ACL-deficient knees. In posterolateral corner reconstruction and medial-sided knee surgery, the deep MCL layers are identified separately from the superficial MCL. The coronary ligament restriction of meniscal movement means deep MCL tightness can be a cause of medial compartment pain mimicking meniscal pathology.
High-grade valgus knee injury disrupts both the superficial MCL and the deep MCL (coronary ligament), producing medial instability that may not fully respond to MCL healing alone; combined deep and superficial MCL repair or reconstruction restores medial compartment stability in grade III injuries with associated ACL disruption.
