MCL injuries require that a valgus (twisting outwards away from mid-line) and/or external rotation load be placed on the knee. Valgus loads can occur through contact, non-contact, and over-use mechanisms. Contact mechanisms, commonly associated with a blow to the lateral knee, involve large valgus stresses and often result in a complete MCL tear. Non-contact valgus and external rotational stresses, observed in cutting, pivoting, and deceleration motions of the leg (e.g., skiing), frequently cause partial tears of the MCL. Finally, over-use mechanisms may be observed in sports such as swimming (breast stroke whip kick) and gymnastics, which place repetitive valgus loads across the knee joint.