Injury to medial collateral ligament of knee (MCL)

Injury to medial collateral ligament of knee (MCL)

Mitsutoshi Hayashi

Mitsutoshi Hayashi

Doctor of Medicine, specialist in the Japanese Society of Rehabilitation Medicine, specialist in the Japanese Society of Orthopaedic Surgery, specialist in the Japanese Society of Rheumatology, staff to strengthen JOC, and sports physician certified by the Japan Sports Association

Medial collateral ligament (MCL) injury

The medial collateral ligament of the knee is easily damaged by tackles, etc.

Disease Overview

The medial collateral ligament of the knee (MCL) gets injured most frequently of all ligament injuries and is often recognized simply as a knee sprain. If it is fixed appropriately in an early stage, it could be repaired more easily (compared with anterior cruciate ligament rupture). But when it becomes chronic (being stretched without treatment in the acute stage), it could cause complications such as meniscal injury, therefore appropriate treatment is essential.

Cause and mechanism of onset


The MCL consists of three layers: the superficial layer, the deep layer, and the posterior oblique ligament. The MCL runs from the medial femoral epicondyle to the medial tibia of the medial knee joint, with the range of a length of 10 cm and a width of 3 cm.

Cause of the injury

In contact sports, such as rugby, American football, football (soccer) , and basketball, external forces (tackles) from the lateral to the medial aspect of the knee may cause the MCL to become overly tense and eventually more susceptible to rupture when valgus or external rotation forces are applied to the joint. The injury may also occur when falling in skiing, jump landing or twist.


In tenderness, swelling, a feeling of warmth and load on the medial joints, valgus laxity (as like X leg) are identified. Immediately after the injury, joint hematoma is present. On the other hand, when it becomes chronic, edema is present.
In general, the injuries are classified into three types and the classification is utilized for treatment guide.
Grade I: no laxity (compared to the unaffected side), and ligament tenderness is predominant
Grade II: valgus laxity in extension (-), valgus laxity (+) in 30 degrees flexion
Grade III: valgus laxity (+) in extension and valgus laxity (+) in 30 degrees flexion



As the X-ray does not show the ligaments, the purpose is to check for fractures. Stress X-rays (Photo 1) and instrumental checks are helpful to determine the degree of injury. Magnetic resonance imaging (MRI) is the most helpful inspection and enables to confirm not only MCL injuries, but also ACL and meniscal injuries as well as hemorrhage.

MCL rupture on X-ray

Photo 1: Distraction of the medial joint by an X-ray with MCL rupture

Combined injury

Although also the isolated injuries occur in common, the injuries on the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), or medial (lateral) meniscus could be caused. Combined injury of the ACL, MCL and medial meniscus is also called the unhappy triad.

Treatment and rehabilitation


RICE therapy is usually given in grade I and conservative treatment by immobilization is done in grade II. Anti-inflammatory analgesics and physical therapies such as ultrasound and low-frequency therapy are used to control pain. Primary suturing of the ligament is performed for grade III injuries and combined anterior cruciate ligament (ACL) and meniscal injuries. Conservative treatment with cast immobilization and nowadays brace immobilization has been used for isolated injuries with good results.

Posttraumatic rehabilitation

In the initial stage, trainings on unaffected side and trunk of upper extremity are performed such as isometric training, straight leg raising ( SLR training) and simultaneous contraction exercises of flexor and extensor around the knee. Because a pain tends to be relieved three weeks after injury, the person may gradually begin to perform range of motion (ROM) of the knee joint and gait exercises with a brace.


Isolated injuries are relatively stable with appropriate immobilization in the initial stage, but they are more likely to loosen when being associated with ACL injury. Loosening of the MCL may occur meniscal injury afterward.

Important point

Accurate diagnosis based on injury level and appropriate fixation are important at the time of injury.

Yoshizumi Iwasaki

Yoshizumi Iwasaki

NATA certified athletic trainers, certified athletic trainers from the Japan Physical Education Association, and chairman of the Japan Core Conditioning Association (JCCA)

Trainer's edition


The medial collateral ligament of the knee is the ligament that is located on the medial side of the knee joint and connects the femur to the tibia. It is important to be ready to protect the knee joint from strong external forces as the athletes with malalignment of their knees are more likely to get injured. For example, the following countermeasures can be done to align with specificity of each athletic event:
・ Strengthen the knee by conditioning
・ Protect with supporters , braces, etc.
・ Reinforce the knee by taping in rainy weather

On-site evaluation and first aid

Many people tend to get injured when the joint is forcibly produced eversion by strong external force to the knee joint from lateral side. The athletes would describe “the knee gets to set in medially”. If there are obvious deformities, swelling, discoloration or a feeling of warmth at the time, treat with icing or splinting and transfer to a medical facility where MRI is available. Even if there is no visible abnormality, make sure to seek medical attention immediately in case that below the knee is apparently immobilized (a positive valgus stress test, Photo 2). Even an athlete who feels a twisted and swollen knee may sometimes try to return to practice or a game. Be sure to restart after the doctor permits . Then, after taking measures such as taping, make sure to do the resumption test to confirm whether the person can practice. In the knee resumption testing, let the person do the following movements after implementing preventive measures of recurrence such as taping: (1) standing with one leg with closure eyes, (2) jumping in place, and (3) hopping on one leg. If these can be accomplished, the person can go to the athletic field and gymnasium to test by (4) making a dash, (5) doing side step and (6) changing direction. In addition, check the movements according to the type , level, and player’s position with a manager or coach to determine if the player should resume while finally returning to practice and game.


Make sure to follow instructions of doctors or physical therapist for rehabilitation immediately after the injury. Even after the person returns to the sports scene, medical professions will prescribe training that is close to the actual movement in sports while continuing the basic menu. In the hospital, strengthening of the surrounding muscles would be done with SLR, Proprioceptive Neuromuscular Facilitation (PNF) and isokinetic exercise.

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