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What is an MCL Injury?

The medial collateral ligament (MCL) is located on the inner side of your knee and connects the thigh bone (femur) and the shinbone (tibia). It's one of the major ligaments connecting the bones in your knee and providing stability to the joint.

The MCL ligament allows the knee joint to move but at the same time remain stable, preventing it from moving side to side. An injury to your MCL can range from a mild sprain or partial tear to a complete grade 3 rupture. A torn MCL can be painful, impair your ability to walk, and make it feel like you can’t hold your weight.

What are MCL tear symptoms?

The most noticeable MCL tear symptom is pain on the inside of your knee directly over the ligament. You may also hear and feel a “popping” sensation in your knee at the time of injury. Other common symptoms include bruising, knee instability, swelling, and the inability to hold your weight.

What are the grades of an MCL injury?

MCL injuries are categorized based on the severity of the injury.

A grade 1 MCL injury is a mild sprain that can be caused by direct trauma to the knee. MCL sprains are common injuries for athletes playing sports such as football, soccer, and tennis. In this type of tear, the knee remains stable but will likely be painful and tender.  

With a grade 2 MCL tear, the ligament is moderately damaged with a partial tear, and you might notice your knee is loose. This type of injury is usually quite painful and accompanied by tenderness and swelling of your knee. In some cases, you might need surgery to recover from a grade 2 tear.

A grade 3 tear is the most severe MCL injury when your ligament is completely torn. With a grade 3 tear, your knee will be loose and painful. This type of tear can often accompany other damage to your knee, such as an ACL tear.

Risk factors and causes of MCL injuries

You are at a higher risk of a torn MCL if you play high-impact sports such as football or martial arts. Sports that involve lots of jumping, sprinting, and quickly changing directions are also high-risk.

MCL injuries are usually caused by getting struck in your knee or by bending or twisting the joint too forcefully, causing the ligament to stretch and tear. Wear and tear of the ligament over time through repeated stress and pressure, such as lifting heavy objects, can also cause injury to the MCL.

How are MCL injuries diagnosed?

Your doctor will conduct a physical exam to determine your injury and the extent of the damage to the ligament. They will test the stability of your knee and check if the joint is loose and unstable. MCL injuries are often diagnosed from a physical exam alone, but your doctor may also complete the following tests to see how bad the sprain or tear is:

  • X-rays, which can help rule out further damage such as a broken or fractured bone.
  • Magnetic resonance imaging (MRI) or ultrasounds, which generate images of the tissues in your knee to show ligament tears or damaged cartilage.

How are MCL injuries treated?

Most MCL injuries do not require surgery to make a full recovery unless other ligaments such as the ACL are also significantly damaged. Unlike the ACL, the MCL has a good blood supply, making it easier for the ligament to heal.

Depending on the severity of your injury, your MCL should be able to heal on its own with adequate time and care. Nonsurgical treatment options include:

  • Resting
  • Icing and elevating the injured knee to reduce swelling and pain
  • Using crutches for extra support as you heal 
  • Wearing a knee brace to provide compression and extra stability
  • Engaging in physical therapy exercises to regain strength and mobility in your knee

While most MCL injuries do not require surgery, your doctor may recommend a procedure for severe tears or injuries that include other structures in your knee. If you’re an athlete, your doctor may also recommend surgery to ensure the ligament can handle the ongoing pressure and stress of sports.

Depending on your injury grade, surgery involves either reattaching the torn MCL or reconstructing the ligament using a tissue graft.

Mass General Brigham Sports Medicine physicians work on the most cutting-edge sports medicine research, technology, and treatment. We specialize in various nonsurgical and surgical treatment options for the full spectrum of knee conditions.

Preventing MCL injuries

The best way to prevent an MCL injury is to condition the muscles in your leg that protect your knee. Strength training combined with stretching can improve your flexibility and the stability of the ligaments surrounding the knee joint.

Other tips for avoiding MCL injuries include:

  • Warming up and cooling down before and after exercise to prepare your body for strenuous activity and promote recovery
  • Wearing proper footwear for better cushioning and support 
  • Using a knee brace during training to increase knee stability and reduce the chance of it buckling or bending incorrectly

Recovering from MCL injuries

The best way to recover from a torn or sprained MCL is to give your body adequate rest and avoid high-impact activity. Physical therapy focused on strengthening your knee and improving flexibility is especially vital for athletes that want to keep playing sports.

Recovery time for a mild MCL sprain is typically about 3-4 weeks, while more severe grades of MCL tears can take up to 12 weeks to heal. If you underwent surgery, your recovery time might take longer.

If you need help recovering from and preventing future MCL injuries, Mass General Brigham Sports Medicine team can develop a customized treatment plan tailored to your unique needs and goals. Request an appointment or call us at 617-726-0500 to learn more. Same-day telehealth virtual visits are often available to speak with one of our specialists.


The MCL is a ligament on the inner side of your knee.

The ligament often makes a distinct popping sound or sensation during injury. Your knee will likely be painful, you may feel unstable, and walking will be difficult. The area will likely swell up and feel tender shortly after the injury.

You might be able to walk on a grade 1 tear, although it will likely be painful. The knee often comes loose during serious MCL injuries, making it difficult to put weight on your leg and hold yourself upright without the help of crutches.

Your knee will likely swell, bruise, and be tender after an MCL injury, making it difficult to bend your knee or do routine activities such as climb stairs or sit in a chair. Stiffness and pain are common symptoms of a torn MCL.

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