MCL injury

The medial collateral ligament (MCL) runs along the inner side of the knee, connecting the thighbone to the shinbone, and keeps the knee from bending inward. It is one of the most frequently injured knee ligaments. Most MCL injuries come from a blow to the outer side of the knee or from a sudden change of direction, and many heal well without surgery.

• Pain and tenderness along the inner side of the knee
• Swelling
• A pop at the time of injury
• Stiffness and difficulty bending the knee fully
• A feeling that the knee is unstable or wants to buckle, more common with severe tears

An MCL injury happens when a force pushes the knee inward, stretching the ligament on the inner side.

• A hit to the outer side of the knee, as in football, hockey, or rugby
• Cutting, twisting, or a sudden change of speed
• Skiing falls in which the lower leg is forced outward
• Weak leg muscles or a previous knee injury

The MCL is often injured together with the ACL or the meniscus.

A clinician examines the knee and gently stresses the ligament, comparing the injured side with the healthy side. Injuries are graded by how much the ligament is damaged:

• Grade 1: the ligament is stretched but intact, and the knee is stable
• Grade 2: a partial tear, with some looseness
• Grade 3: a complete tear, with clear looseness when the knee is stressed

X-rays look for a fracture or a piece of bone pulled off with the ligament; in children and teens, they also check the growth plates, which can be injured in a similar way. An MRI is used for more severe injuries or when other damage inside the knee is suspected.

Most MCL injuries heal without surgery, because the ligament has a good blood supply. Treatment usually includes rest, ice, compression, and elevation; anti-inflammatory medication when appropriate; crutches for a short time if walking is painful; and a hinged knee brace that protects the ligament from side-to-side stress while still letting the knee bend. Physical therapy restores motion and strength.

Surgery is uncommon for an MCL injury on its own. It may be considered when the ligament is torn in a way that is unlikely to heal, when the knee stays unstable after a period of bracing, or when the MCL tear is part of a combined injury that also involves other ligaments such as the ACL.

Mild sprains often allow a return to activity fairly soon, while complete tears take longer. Return to sport is guided by pain, swelling, strength, and the stability of the knee rather than a fixed schedule, and it is usually gradual. Some athletes wear a brace when they first go back to play.

Keeping the leg muscles strong and flexible and using good technique when cutting and landing help protect the knee. In some contact sports, players wear protective knee braces intended to lower the risk of MCL injury; ask your clinician whether one makes sense for your sport.