Explanation:
The medial collateral ligament (MCL) is the primary stabilizer against valgus stress at the knee joint. It extends from the medial femoral epicondyle to the proximal tibia. The ligament also contributes to rotational stability of the knee. MCL injuries commonly occur during contact sports when a valgus force is applied to the knee. Many isolated injuries can be treated conservatively with bracing and rehabilitation. Severe injuries or combined ligament damage may require surgical intervention. Reference: Fetto JF. "Medial Collateral Ligament Injuries of the Knee." Clinical Orthopaedics and Related Research, 1978.