Decoding the Medial Collateral Ligament: A Layered Approach to Understanding the Magnetic Resonance Imaging Injury Patterns

Purpose or Learning Objective: To review the layered anatomy of the medial collateral ligament and apply it to magnetic resonance imaging injury patterns.

Methods or Background: The medial collateral ligament is a flat ligament with three layers:

1. Superficial (layer I): The deep crural fascia, continuous with the fascia of the vastus medialis and sartorius.

2. Intermediate (layer II): The tibial collateral ligament proper, the primary valgus stabilizer, particularly during knee flexion, and a secondary stabilizer against external rotation.

3. Deep (layer III): The deep meniscofemoral and meniscotibial capsular ligaments that provide secondary rotational stability and limit excessive valgus. Posteriorly, the intermediate and deep layers fuse to form the posterior oblique ligament, the primary restraint against excessive internal rotation. Medial collateral ligament injuries typically result from direct valgus forces or sudden directional changes, and they often coexist with other injuries, particularly of the anterior cruciate ligament. The two main mechanisms are straight valgus instability and anteromedial rotary instability.

Results or Findings: Medial collateral ligament injuries present with medial knee pain, localized tenderness, joint effusion, and valgus laxity. Magnetic resonance imaging is essential for grading:

Grade 1: High signal within the medial to tibial collateral ligament, indicating deep crural fascia injury (layer I).

Grade 2: High signal within the tibial collateral ligament with or without focal thinning and/or high signal deep to the tibial collateral ligament due to injury to the meniscofemoral or meniscotibial capsular ligaments (layer II).

Grade 3: Complete medial collateral ligament disruption. Secondary signs of injury are medial femoral condyle marrow edema, increased laxity or a wavy medial collateral ligament appearance, especially with distal injury, and lateral compartment bone bruising in cases of direct valgus forces. Chronic injuries may show a Pellegrini-Stieda lesion. Medial collateral ligament injury mimics are pes anserine/medial collateral ligament bursitis, medial meniscal tears, osteoarthritis, cellulitis, and trauma. Hydroxyapatite deposition disease can mimic a Pellegrini-Stieda lesion.

Conclusion:  Grade 1 and 2 medial collateral ligament injuries typically heal with conservative management with early mobilization and a hinged knee brace. Grade 3 injuries may require surgery, particularly with severe valgus alignment, a Stener-like lesion with interposition of the pes anserinus fibers between the distal medial collateral ligament attachment and the tibia, or additional bony avulsion or ligamentous injuries.

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Artikel online veröffentlicht:
02. Juni 2025