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.
Linda J. Vorvick, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine; and C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.