The medial collateral ligament (MCL) is one of four ligaments that are critical to the stability of the knee joint. A ligament is made of tough fibrous material and functions to control excessive motion by limiting joint mobility. The four major stabilizing ligaments of the knee are the anterior and posterior cruciate ligaments (ACL and PCL, respectively), and the medial and lateral collateral ligaments (MCL and LCL, respectively).

The MCL spans the distance from the end of the femur (thigh bone) to the top of the tibia (shin bone) and is on the inside of the knee joint. The medial collateral ligament resists widening of the inside of the joint, or prevents “opening-up” of the knee.

Because the MCL resists widening of the inside of the knee joint, the MCL is usually injured when the outside of the knee joint is struck.

This action causes the outside of the knee to buckle, and the inside to widen.  When the MCL is stretched too far, it is susceptible to tearing and injury.

This is the injury seen by the action of “clipping” in a football game.

An injury to the MCL may occur as an isolated injury, or it may be part of a complex injury to the knee.

Other ligaments, most commonly the ACL, or the meniscus (cartilage), may be torn along with a MCL injury.

Symptoms of a MCL injury tend to correlate with the extent of the injury. MCL injuries are graded on a scale of I to III.

Grade I MCL Tear

This is an incomplete tear of the MCL. The tendon is still in continuity, and the symptoms are usually minimal. Patients usually complain of pain with pressure on the MCL, and may be able to return to their sport very quickly. Most athletes miss 2-4 weeks of play.

Grade II MCL Tear

Grade II injuries are also considered incomplete tears of the MCL. These patients may complain of instability when attempting to cut or pivot. The pain and swelling is more significant, and usually a period of 4-6 weeks of rest is necessary.

Grade III MCL Tear

A grade III injury is a complete tear of the MCL. Patients have significant pain and swelling, and often have difficulty bending the knee. Instability, or giving out, is a common finding with grade III MCL tears. A knee brace or a knee immobilizer is usually needed for comfort, and healing may take 6 weeks or longer.

If you have a mild MCL strain, it can heal on its own with rest, ice, and other self-care. You’ll need to raise your sore knee when you put ice on it, keep weight off the joint, and protect and compress the injury with a knee brace or elastic bandage.

To ease pain and swelling, your doctor may have you take NSAIDs (nonsteroidal anti-inflammatory drugs) like aspirin, ibuprofen, or naproxen. Follow the instructions on the label.

For more severe damage, you may need physical therapy to rehab your knee when your MCL pain begins to fade. Your physical therapist will give you exercises to strengthen the leg muscles around your knee so it works properly.

It’s rare for someone with an MCL injury to need surgery, since this ligament can often heal within a few weeks or months with the help of other measures. But you might need it, especially if another part of your knee is also hurt.

Whether or not you need surgery, you may be able to play sports again with a few weeks or months. Your doctor can let you know when it’s OK to get back to those activities, and she may ask you to wear a knee brace when you’re active.