What is Medial Collateral Ligament Knee Injury?
The medial collateral ligament (MCL) is a kind of tissue that is like a flat strap. It runs from the large bone in your thigh (femur) to the large bone in your lower leg (tibia), specifically connecting the two from the inside (medial side). The main job of the MCL is to help keep the knee joint steady when it moves side to side. Injuries to the MCL are common in sports, and it’s noteworthy that 60% of knee injuries from skiing involve this ligament.
What Causes Medial Collateral Ligament Knee Injury?
Medial collateral ligament, or MCL, injuries often happen when the knee is suddenly twisted or turned. They can also occur if a sharp blow is delivered to the outer side of the knee, creating what’s known as ‘valgus’ stress (that’s a medical term for force pushing the knee inwards). MCL injuries can happen on their own, but it’s more common for them to occur alongside injuries to other parts of the knee.
For instance, there’s a type of injury known as the “unhappy triad”. This happens when the MCL, the anterior cruciate ligament (that’s another major ligament in the knee), and the medial meniscus (which is a piece of cartilage that acts as a cushion in your knee) are all damaged at the same time.
Risk Factors and Frequency for Medial Collateral Ligament Knee Injury
About 40% of all knee injuries are due to ligament damage. Within this category, the most common type is an injury to the medial collateral ligament (MCL).
Signs and Symptoms of Medial Collateral Ligament Knee Injury
People experiencing a medial knee injury can have sudden or persistent internal knee pain. In situations where the injury was recent, patients usually recall a particular incident triggering the pain or swelling, like an incident during a sports event. Often, they heard or felt a pop when the injury happened. They may also struggle with walking and feel like their knee is unstable.
A physical examination is often how these injuries are identified. This can happen immediately after the incident or can be identified later when the individual seeks medical help.
The doctor might notice swelling in the joint or bruising either at the inner knee or the outer knee from the ligament damage during the examination. The swelling should be concentrated around the medial collateral ligament (MCL) and usually does not involve the entire knee. Often, patients can walk normally, but sometimes they may demonstrate an awkward or pained gait.
The doctor will then feel along the entire length of the MCL. If there’s a specific point of tenderness, it may indicate the locale of the injury. Depending on the precise location of this tenderness, it may be confused with injuries to other parts of the knee. Testing the stability of the MCL is done using a valgus stress test. During this procedure, the patient will lie down and their leg will be positioned off the table. The doctor will move the ankle to the side while applying outward pressure to the knee. From this test, they can classify the injury into the following types:
- Grade 1 – Pain but little or no joint movement
- Grade 2 – Some opening of the joint but with a clear limit
- Grade 3 – Significant joint opening, no limit to movement
The test is then performed again, this time with the knee fully extended. If the knee is still unstable, the injury may not be limited to the MCL.
Testing for Medial Collateral Ligament Knee Injury
If a doctor suspects that a patient has injured their medial collateral ligament, or MCL (one of the ligaments in the knee), they may use a variety of imaging techniques to confirm this and check for any other related injuries. These can include standard X-rays, which can reveal hidden fractures or torn-off bone fragments. In particular, a Pellegrini-Stieda lesion is a calcification near the femoral epicondyle (the bump at the bottom of your thigh bone) where the MCL attaches, and can indicate an old MCL injury.
Stress radiographs may also be done, particularly in younger patients whose skeletons are still growing. This involves taking X-rays while the joint is being stressed or moved in certain ways.
However, the preferred imaging test for MCL injuries is a Magnetic Resonance Imaging (MRI) scan without contrast (a substance used in certain MRI scans to enhance visibility of various structures). Besides examining the MCL directly, an MRI can also provide important details about other soft tissues in the knee and help detect any additional injuries. If the doctor suspects damage to the knee’s meniscus (cartilage) or capsule (a fibrous tissue that encloses the joint), they may use a type of MRI called MR arthrography.
Another option is ultrasound, which is faster, more portable, and cheaper than an MRI. Ultrasound was able to identify the location and severity of MCL injuries in 94% of patients studied, and it also allows for a dynamic valgus stress test, which checks how the knee moves under stress and helps assess the injury.
Treatment Options for Medial Collateral Ligament Knee Injury
In many cases, injuries that are classified as Grade I or II are treated with a gentle approach, unless there is an additional severe injury that needs surgery. Doctors might recommend non-steroidal anti-inflammatory drugs (NSAIDs), which are medications to reduce pain and swelling. For a short period after the injury, the use of a knee brace and crutches might be suggested, with a gradual decrease in their use as the pain and swelling go down and the capacity for physical therapy improves.
The patient may be guided through a series of exercises during physical therapy. These could include strengthening the quadriceps (thigh muscles), cycling, or other resistance exercises. The goal is to gradually increase the difficulty level of the exercises, along with the re-introduction of specific sports movements. People with Grade I injuries generally get back to playing their sport within 10 to 14 days. However, those with Grade II injuries should only return once their legs show equal strength and no pain is experienced during testing for flexibility and movement.
Nearly all athletes with Grade I and II injuries recover well with this conservative treatment.
In the case of Grade III injuries, the treatment might be conservative or it could involve surgery. Surgery is often the chosen route for athletes because these injuries can cause lasting instability in rotation. Grade III injuries often come with additional injuries that require surgery, like an Anterior Cruciate Ligament (ACL) tear. In the case of a fresh tear, repair is typically possible, but if it’s a long-standing tear, reconstruction using allograft (transplant tissue from a donor) or autograft (transplant tissue from the patient) might be required.
Post-surgery, the patient may be advised to wear a specialized brace, which allows for a limited knee bend of 30 degrees, and to put only their toe-weight on the leg for about three weeks. During this time, exercises that move the knee up to 90 degrees could be done, along with strengthening exercises while wearing the brace. After three weeks, the weight on the leg can be gradually increased and the brace adjusted for full range of knee motion. Following this, the patient can progress to more advanced exercises for enhancing strength and stability.
What else can Medial Collateral Ligament Knee Injury be?
Some conditions that can cause pain or inflammation in the knee include:
- Crystal-induced inflammatory arthropathy: a condition caused by crystalline deposits in the joints
- Infection: any viral or bacterial infections in the knee
- Osteoarthritis: a disease that causes the joints to wear down over time
- Overuse syndromes: conditions that arise from using the knee excessively
- Patellar subluxation: partial dislocation of the kneecap
- Patellar tendonitis: inflammation of the tendon connecting the kneecap to the shinbone
- Popliteal cyst: a fluid-filled cyst behind the knee
- Slipped capital femoral epiphysis: a disorder where the thigh bone slips off the hip joint
- Tibial apophysitis: a condition commonly affecting young athletes that causes pain on the front of the knee
- Trauma: any injury to the knee
