Anterior Cruciate Ligament Rupture

Anterior Cruciate Ligament Rupture

The anterior cruciate ligament or ACL is one of the major stabilisers of the knee. It is a strong ligament that is important in controlling twisting movements of the knee particularly during sports and in any activity involving quick change of direction. The injury usually happens when the foot is planted on the ground and the upper body twists away from the direction in which the foot is facing with the knee slightly bent. (See diagram below)

Body Part Many patients describe hearing something ‘pop’ in their knee. The injury is followed by pain and rapid swelling and one is unable to continue playing. Instability of the knee persists usually with difficulty returning to the sport even after a few weeks.


The ACL controls the forward movement of the lower leg on the thigh bone. It allows for rapid change in direction when walking or running.


With an acute ACL injury you typically have pain and swelling. Normally you are unable to return to sport and avoid turning movements. After a few months you may be able to resume sport but you often have further episodes of the knee giving way. Pain may suggest further damage to the knee and should always be assessed by an orthopaedic surgeon.


The goal of treatment is to provide a stable knee that allows participation in desired activities. In active individuals the return to sports is important. However, even in some non sporting individuals the feeling of instability often requires further attention.

Immediately following injury, pain and swelling normally limits most things including a full assessment. The knee is allowed to settle down by resting, elevation and the application of ice.

After the full assessment gentle rehabilitation should start to work on the front and back thigh muscles to improve knee control and reduce swelling. With good physiotherapy supervision many people return to good function without residual instability.

If after supervised rehabilitation with physiotherapy there is still persisting instability or pain, you will need to see an orthopaedic surgeon to discuss reconstruction of the ACL.

After surgery it normally takes 9 – 12 months before you are able to return to sports.