May also be called: MCL Injury; MCL Tear

An MCL injury is a tear in one of the ligaments in the knee.

More to Know

The MCL is one of the four main ligaments in the knee joint. It is located on the inner side of the knee — the side that is closest to the other knee. The MCL works together with the lateral collateral ligament (LCL), which is in the same location on the outside of the knee. These two ligaments help prevent the knee joint from overextending from side to side.

MCL injuries are common, especially among kids and teens who play contact sports like football. The injury happens when the outside of the knee is struck, causing it to unnaturally bend inward toward the other knee. MCL tears usually cause swelling and pain within the first 24 hours of injury. If you suspect an MCL injury, stop all activity, keep the area iced and elevated, avoid putting weight on the knee, and call your doctor.

Keep in Mind

Although most MCL injuries heal on their own with anywhere from 1 to 6 weeks of rest, most still require rehabilitation ("rehab") therapy to help regain strength in the joint.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.