The medial collateral ligament (MCL), otherwise known as the tibial collateral ligament, stabilizes the knee against valgus forces. The MCL is the most commonly injured ligament in the knee. The mechanism of injury includes a direct blow to the lateral knee, creating valgus stress.

The MCL most commonly tears at the femoral insertion, and tears at this site have improved healing rates over tears that occur distally at the tibial side. The most common grading system used to define MCL rupture describes the degree of laxity with valgus stress. A valgus load is placed with the knee in 20 to 30 degrees of flexion, and laxity is described as grade I, grade II, or grade III. Grade I is a first-degree tear with tenderness to palpation over the MCL but without laxity. Grade II is a second-degree tear with partial tearing of the MCL. In grade II tears, laxity can be felt with valgus stress, but the fibers are still opposed, so a firm end point is noted. Grade III is a complete rupture of the MCL with gross laxity and no end point felt with valgus stress.1,2

Magnetic resonance imaging is often ordered after MCL injury if associated damage such as bone bruising, meniscal tears, and anterior cruciate ligament tears cannot be ruled out. Isolated grade I and II MCL tears are treated nonoperatively with a hinged knee brace and protected weight bearing. Physical therapy is initiated for supervised strengthening and stretching.

Those with grade I tears may return to sports in 7 to 10 days with a brace if tolerated. Those with grade II injuries generally must not participate in sports for 4 to 6 weeks and occasionally longer if the tear occurs at the tibial side. Most grade III injuries are treated nonoperatively with a hinged brace for 6 weeks. Progressive weight bearing and strength training is continued throughout the period of bracing. A custom MCL brace may be worn longer in athletes at high risk for re-injury, including those who participate in sports like hockey and football. Operative treatment may be considered for those with complete rupture on the tibial side, those with multiligament knee injuries, and those who have continued laxity and disability despite conservative treatment.1

Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).


  1. Jones T, McCulloch P. MCL Knee Injuries. Updated December 12, 2014. Accessed September 27, 2016.
  2. Wijdicks CA, Griffith CJ, Johansen S, Engebretsen L, LaPrade RF. Injuries to the medial collateral ligament and associated medial structures of the knee. J Bone Joint Surg Am. 2010;92:1266-1280.
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