Medial collateral ligament (MCL)... Image

The medial collateral ligament connects the end of the femur (thigh) to the top of the tibia (shin bone. The medial collateral ligament provides stability against valgus stress. A valgus stress is described as a pressure applied to the leg that tries to bend the lower leg sideways at the knee, away from the other leg. Tackling in football or soccer are two common causes of this injury.