The anterior cruciate ligament (ACL) prevents anterior translation of the tibia on the femur and contributes to resistance to internal and external rotation while the knee is extended. It is a secondary stabilizer to valgus stress in full extension. The medial collateral ligament (MCL) resists valgus stress at 30 degrees of knee flexion. It also contributes to limiting anterior and posterior translation, as well as rotation, of the tibia. Thus, when both ligaments are disrupted, the knee can bec ...
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