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Medial Collateral Ligament (MCL) Tear

What is the MCL?

The medial collateral ligament (MCL) is a major ligament (a thick band of tissue that connects bones and joints) located on the inside of your knee. It is one of four ligaments that stabilize the knee joint. The other primary ligaments include the anterior cruciate ligament (ACL), lateral collateral ligament (LCL), and the posterior cruciate ligament (PCL).

The main function of the MCL is to prevent the leg from turning inward, while also allowing it to rotate. Since the MCL runs from your femur (thigh bone) to the top of your tibia (shin bone), it can be extremely painful when the ligament is torn or overstretched.

If the outside of the knee joint takes a direct hit (such as when playing sports), the ligament on the inside of the knee may stretch too far. This can cause the MCL to tear. A partial MCL tear is an incomplete but significant tear, while a complete tear is a severe tear where the MCL is completely torn. An MCL tear can happen in conjunction with an ACL tear, and possibly other ligaments in the knee.

For people who play sports that require frequent turning and pivoting, such as skiing, football, and basketball, damage to the MCL is a common injury. The sudden and forceful turns (called “cutting” in sports) involved in these types of activities can cause an MCL tear. It can also happen when the outside of the knee takes a direct hit, such as during a football tackle, causing the ligaments on the inside of the knee to stretch too far or tear.

Other situations that can lead to a torn MCL include:

  • Repeated stress injury, which causes the MCL to lose its normal stretch and elasticity, similar to a stretched out rubber band.
  • Hyperextending (overstretching) your knee, which can occur when you land wrong after a jump.

Your healthcare provider will conduct a physical exam to check for pain and tenderness along the inside of the knee. They will also put pressure on the outside of the knee, while both bent and straight, to check the integrity of the MCL. After determining the degree of pain and laxity of the joint, your injury will be described as one of three grades:

  • Grade 1: A grade 1 MCL tear would likely involve tenderness and minor pain. This would be a mild tear where less than 10% of the ligament is torn, and your knee is still stable.
  • Grade 2: A grade 2 MCL tear involves major pain and tenderness along the inside of the knee, and potentially some swelling. The superficial part of the MCL is partially torn, and the knee opens up approximately 5 milliliters when the doctor moves your leg around.
  • Grade 3: A grade 3 MCL tear is when your MCL is completely torn, often in combination with an ACL tear and sometimes in conjunction with a PCL tear. The pain is intense, and there may be some swelling and marked joint instability (approximately 10 milliliters when manipulated).

If the pain and swelling from a recent injury interfere with your doctor’s ability to make an immediate diagnosis, they may ask you to wear a light splint, keep the knee elevated, and apply ice. Once the pain and swelling have gone down, your healthcare provider will be able to make a diagnosis.

Your doctor may order one of the following tests to determine if there are other injuries or damage associated with the MCL tear:

  • X-ray: An x-ray is useful for showing broken bones or other injuries in the knee.
  • Stress X-ray: In this type of x-ray, the technician will hold the knee open from the side to measure the amount of side-to-side gapping. This can be compared with the healthy knee, which is helpful since there can be considerable variance between patients in the amount of normal gapping that can occur.
  • Magnetic resonance imaging (MRI): An MRI is 90% accurate in diagnosing and classifying an MCL tear. This is the imaging test most often ordered for a suspected MCL tear, and also helps determine if there are other soft tissue injuries in your knee.
  • Ultrasound: This test uses sound waves to help your provider see the severity of your MCL tear, and if there are related injuries.

To determine a treatment plan, your doctor will ask you about your medical history (such as previous knee injuries), how you injured your knee, and about your physical and athletic goals after recovery.

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