Medial Collateral Ligament (MCL) Sprain


The medial collateral ligaments are the most common ligaments to be sprained in the knee. They are found in the inside part of the knee between the femur (thigh bone) and the tibia (shin bone).

The MCL works predominantly with the ACL (anterior cruciate ligament) to resist valgus stress (forces pushing outside of the knee inwards or forces pushing the lower end of the shin bone and foot outwards). It’s especially vulnerable when the knee is flexed (bent). A good example of this can be seen when a footballer gets kicked in the inside of his foot or leg. The MCL also restricts external rotation of the lower leg (actions which turn the foot out). This is why this ligament is commonly injured during skiing; when the ski moves away from the body it creates a significant torsion (twisting) force at the knee. The MCL acts with the ACL to resist such forces and they are frequently injured together in skiing and contact sports. If an individual is very unfortunate, they may damage three knee structures at once – this is commonly known as the ‘unhappy triad’ and involves interruption of the MCL, ACL and meniscus (pad of cartilage).

It’s also important to understand that the MCL can be injured by repetitive lower grade trauma. These are often more difficult for the patient to realise and can be as subtle as sitting in a certain position or running on sloped or soft surfaces such as beaches. A very important job of any manual therapist is to first prevent this mechanism of injury from reoccurring to allow the ligament to repair.


A thorough history from the patient is taken, which often gives a good indication as to which knee structures may be damaged. This dictates the specific orthopaedic test performed during the initial assessment. The knee will also be examined to see if there is any tenderness or swelling around the ligaments.


Grade I

• Able to fully bear weight (stand) through the knee with negative instability on the valgus stress test.

• No/mild swelling on the inside of the knee.

• Mild/moderate tenderness over ligament.

• Mild pain.

Grade II

• Able to bear weight through the knee with positive instability on the valgus stress test and slightly increased movement.

• Mild to moderate swelling on the inside of the knee.

• Moderate/marked tenderness over ligament.

• Moderate/severe to marked pain.

Grade III

• May be able to bear weight through the knee, but aware of significant instability (feeling of giving way) with positive instability on the valgus stress test.

• Mild to moderate swelling on the inside of the knee.

• Moderate/marked tenderness over ligaments.

• Moderate/severe pain.

Ligaments cannot be seen on x-ray and, due to their close proximity to bone, ultrasound imaging is often of little use in this region. Therefore, MRI scans tend to be utilised when assessing suspected severe ligamentous injuries.

(The list of conditions given above and subsequent explanations are intended as a general guide and should not be considered a replacement for a full medical examination. Furthermore, we do not purport to treat all the conditions listed. Should you wish to discuss any of these conditions with our chiropractors, please do not hesitate to phone the clinic on 020 7374 2272 or email

Our team of chiropractors and massage therapists are on hand to answer any questions you may have, so get in touch today via or on +44 (0)20 7374 2272.

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