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What is a medial collateral ligament (MCL) injury?

The medial collateral ligament (MCL) is located on the inner aspect, or part, of your knee, but it’s outside the joint itself. Ligaments hold bones together and add stability and strength to a joint.

The MCL connects the top of the tibia, or shinbone, to the bottom of the femur, or thighbone.

An injury to the MCL is often called an MCL sprain. Ligament injuries can either stretch the ligament or tear it. MCL injury of the knee is usually caused by a direct blow to the knee. This type of injury is common in contact sports.

It’s usually the result of a hit or blow to the outer aspect of the knee, which stretches or tears the MCL.

MCL injuries can be grades 1, 2, or 3:

  • A grade 1 MCL injury is the least severe. It means that your ligament has been stretched but not torn.
  • A grade 2 MCL injury means that your ligament has been partially torn. This usually causes some instability in your knee joint.
  • A grade 3 MCL injury is the most severe type of ligament injury. It occurs when your ligament has been completely torn. Joint instability is common in a grade 3 MCL sprain.

The symptoms of an MCL injury are similar to symptoms of other knee problems. It’s important for your doctor to examine your knee to determine the problem.

The symptoms of an MCL injury may include:

  • a popping sound upon injury
  • pain and tenderness along the inner part of your knee
  • swelling of the knee joint
  • a feeling that your knee is going to give out when you put weight on it
  • locking or catching in the knee joint

Problems with knee stability typically indicate grade 2 or grade 3 injuries.

Your doctor can often tell if you have an MCL injury by examining your knee. During the examination, your doctor will bend your knee and put pressure on the outside of it. They’ll be able to tell if your inner knee is loose, which would indicate an MCL injury.

It’s important that you relax your leg muscles during the examination. This makes it easier for your doctor to test the stability of your ligaments. You may feel some pain and tenderness in your knee during the examination.

Your doctor may order imaging tests to help diagnose your knee injury. An X-ray will give your doctor an image of the bones in your knee. This can help them rule out other knee problems.

During an X-ray, a technician will position your knee so that the machine can record images. This may cause some pain if your knee is tender or swollen. However, the process will only take a few minutes. The X-ray will tell your doctor if there’s an injury to the bones in your knee.

Your doctor may also order an MRI scan. This is a test that uses magnets and radio waves to produce images of the body.

For an MRI scan, you’ll lie down on a table and a technician will position your knee. The MRI machine often makes loud noises. You may be given earplugs to protect your ears.

The table will slide into a scanner and images of your knee will be recorded. During the MRI scan, you’ll be able to communicate with your technician through a microphone and speakers in the machine.

The images from the MRI will tell your doctor if you have a problem in the muscles or ligaments of the knee.

Treatment options vary depending on the severity of the MCL injury. Most MCL injuries will heal on their own after a few weeks of rest.

Immediate treatment

Immediate treatment is necessary to ease pain and help stabilize your knee. Immediate treatment options include:


As you recover from your injury, the goal is to regain strength in your knee and prevent further injury. Treatments may include:

  • physical therapy to strengthen muscles and improve your knee’s range of motion
  • wearing a protective knee brace during physical activity
  • limiting activities that can cause further injury, such as contact sports


Rarely, an injury to the MCL will require surgery. Surgery is necessary when the ligament is torn in such a way that it can’t repair itself. It’s also done when the MCL injury occurs with other ligament injuries.

Before your surgery, your surgeon may use arthroscopy to thoroughly examine the extent of your injury and to look for associated injuries inside your knee. Arthroscopy involves inserting a small, thin camera through a tiny incision, or cut.

After the arthroscopic exam, your surgeon will make a small incision along the inner aspect of your knee. If your ligament is torn where it attaches to either your shinbone or your thighbone, your surgeon can use one of these to reattach it:

  • large stitches
  • bone staples
  • a metal screw
  • a device called a suture anchor

If the tear is in the middle of the ligament, your surgeon will stitch the ligament together.

The outlook is usually good regardless of whether or not surgery is needed. Recovery times vary depending on the severity of your MCL injury. Since grade 1 MCL injuries are minor, they only take a few days to heal.

Grade 2 injuries, however, can take up to four weeks. Grade 3 injuries are the most severe and have the longest recovery time. It typically takes eight weeks or more for these types of injuries to heal.