MCL Knee Ligament Injury in Depth AKA: Medial Collateral Ligament Injury

Common Signs & Symptoms
Pain Swelling Stiffness Weakness Instability Locking

MCL Injury

The medial collateral ligament is the primary stabiliser of the inner (medial) side of the knee. It is a thick fibrous band and is designed to resist valgus (side-on) forces to the knee.


Pain, swelling and instability are all common with this injury. It is possible that you will lose some joint range of motion and struggle to weight bear initially, if it is a substantial injury.


The onset is usually traumatic and can happen via a direct blow to the outside of the thigh. Or the MCL can be torn when the foot is planted and there is a valgus strain put on the knee. This often happens in football tackling injuries. Occasionally this injury can happen when there is a valgus stress placed upon the knee in conjunction with the femur externally rotating. This type of injury often occurs while skiing.

Tears to the MCL are classified as follows:

Grade 1: Tearing of a few fibres but no ligament laxity or joint instability is present.

Grade 2: Tearing of a substantial amount of fibres, with mild ligament laxity and joint instability present.

Grade 3: A complete tear of the mcl fibres, ligament laxity and joint instability are both present

Aggravating factors:

Valgus knee forces, walking on uneven ground and changing direction sharply when running.

Easing factors:

Avoiding the aggravating factors, using ice and a supportive brace.


Most MCL injuries are successfully managed non-operatively using the principles of POLICE (protection , optimal loading , ice, compression and elevation) under the guidance of a physiotherapist. In cases where there is chronic instability or if there are multiple ligament injuries, surgical intervention may be required.

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