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Knee Ligament Injury

MCL Injury

Minute Read


Posted 10 months ago


Last updated: 29/11/2022


by James McCormack

Ligaments are fibrous connective tissue that attach bones to bones and limit the movement at that joint in a particular direction. The MCL of the knee is the medial collateral ligament, attaching the femur and tibia on the inside of the knee. The MCL is made up of a superficial band and a deep band, both generally speaking are attached to the femur and the tibia.

The superficial MCL is attached superiorly to the medial femoral condyle and inferiorly has two insertion points, one into the semimembranosis tendon (one of the hamstrings) and the second into the upper medial surface of the tibia. The deep MCL is also divided into two, the meniscofemoral and meniscotibial ligaments. The meniscofemoral part attaches from the femur near the superficial MCL attachment, and to the medial meniscus, and the meniscotibial is attached to the medial meniscus and the medial tibial plateaux.

Diagram of medial collateral ligament injury

The Function of the MCL Explained

The main function of the MCL  is to restrict inward movement of the knee, known as valgus movement and it also helps the smooth movement of the knee when a tension force is applied. The superficial MCL also helps stabilise external rotation at 30º of knee flexion, and the deep MCL helps stabilise medial rotation when the knee is 0-90º flexed. There is also some assistance of the MCL in preventing hyperextension of the knee, and the backward movement of the tibia on the femur. An additional function of the MCL is feedback about the joint position to the brain, known as proprioception.

photo of ski injury

What is an MCL Injury?

An MCL injury is when the ligament is stretched its capacity. The fibrous connective tissue is damaged as a result. The most common mechanism of injury is an excessive inward force of the knee, this is commonly the cause when the MCL injury occurs while skiing or with a tackle in rugby, football/soccer. Twisting the knee or hyperextension are other frequent mechanisms of MCL injury, seen in sports. Other sports with a high incidence of MCL injury include jiu-jitsu and wrestling.

Not all injuries occur through sport, a fall or direct blow to the area can cause damage to the ligament. And some people are more at risk than others. If your knee moves inwards when walking, or if you are overweight there will more stress on the MCL and this can cause a chronic injury. During pregnancy, hormones are released that make all ligaments more lax or stretchy so during pregnancy ligament injuries are more common.


It is essential to take a thorough history to hear the symptoms, lifestyle and activity levels of the individual, and if there was a specific mechanism of injury. The examination of the knee should include a general assessment of the person’s movements, strength and mobility, and more specific orthopaedic tests. A valgus stress test is the best MCL injury test that can be used. It should assess the laxity and pain provocation of passively moving the knee into a valgus position with the knee at 0º and 30º of flexion. The measure of excess movement coupled with pain can help to determine the classification and severity of the injury. Other tests should be performed to rule in or out other possible diagnoses. Differential diagnoses include medial meniscus injury, Pes Anserine Bursitis and osteoarthritis


Grade 1 – mild ligament tear

Grade 2 – moderate to severe ligament tear

Grade 3 – complete tear or disruption of function

MCL Injury Symptoms

The signs and symptoms of an MCL injury will vary depending on the severity, mechanism of injury and if any other structures were injured at the same time. The most common symptom is pain location, on the inside of the knee, this may be more intense pain when bending the knee. It might feel like an ache with minor injury or more intense, sharp or burning with more severe injuries. If there is a moderate to severe injury to the ligament there may be bruising and swelling around the inside of the knee. But in many cases, there can be no swelling.

MCL injuries can present with symptoms that include instability or the knee giving out, clicking or popping sensations, or feeling unable to bend or straighten the knee due to pain. The joint pain can be worse at night and many people find it difficult to find a good sleeping position that is comfortable.


In addition to clinical assessment, imaging with MRI,  ultrasound and x-ray can be helpful to rule in the diagnosis of an MCL injury and rule out other conditions. Sensitive imaging such as MRI or ultrasound can also help with the classification of the injury.

Picture of MRI Machine

How long does it take an MCL injury to heal?

Typically ligaments, including the MCL take 6 weeks to heal. In severe cases this can take longer. A clinical diagnosis is needed and an experienced clinician can guide you through the best treatment and management plan. You can read more about treatment in our related article: MCL Injury Treatment.

Physiotherapy with James McCormack

This is not medical advice. We recommend a consultation with a medical professional such as James McCormack. He offers Online Physiotherapy Appointments for £45.

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