Collateral Ligaments

As discussed in the anatomy section, the medial and lateral collateral ligaments (MCL and LCL) keep the knee stable on the outside (LCL) and the inside (MCL). Together these ligaments connect the lower leg (tibia) with the upper leg (femur) and control the side-to-side motion of the knee.

Tears to the collateral ligaments require a sharp blow to the inside or outside of the knee. Damage to the LCL requires a blow to the inside of the knee so this type of injury is relatively rare. Injuries to the MCL are more common and often accompany damage to the anterior cruciate ligament (ACL) and surrounding tissue.