ACL tear

Anterior Cruciate Ligament (ACL) injuries


What is it?

The ACL is one of the main stabilising ligaments of the knee joint.  The ACL is in the centre of the knee and helps control rotation and front to back movement of the shin bone on the thigh bone.  When torn, the lack of this control can lead to the knee giving way when twisting or changing direction.  If this instability is allowed to continue further damage can be done to other structures within the knee such as the articular or meniscal cartilages. 


Why does it occur?

The ACL can be torn when the knee is twisted or hyperextended suddenly during sports such as football or netball.  It is also commonly injured in ski accidents. 


What are the symptoms?

Classically when someone tears their ACL they hear or feel a pop in the knee which is often associated with pain and fairly rapid onset of significant swelling within the knee joint.  Patients are normally unable to carry on doing the activity they were doing at the time of injury. Often they will limp due to pain and restricted range of movement within the knee for a few weeks before things calm down.


With rehabilitation, 20-30% of people with an ACL tear will be able to return to normal activities and sports potentially with the assistance of a brace.  The majority of people however will have some ongoing symptoms such as knee instability or giving way or recurrent pain and swelling.


How is it diagnosed?

As with all musculoskeletal injuries it is important to get an early expert opinion which should include a full history and examination.  This will include specific tests for the ACL to ascertain whether or not your knee is unstable.  It is often possible to diagnose an ACL rupture with these tests alone but normally these findings will be confirmed with an x-ray and MRI scan.  These images will also allow your treating doctor to rule out any potential other injuries to the bone or cartilage.


How is it treated?

  1. Non-surgical treatment

    All patients with an ACL rupture will require physiotherapy in order to reduce the swelling in their knee, regain a full range of movement, strengthen their muscles and to help improve proprioception.  In some instances this may be enough to provide the knee with sufficient stability to return to activity.

  2. Surgical treatment

If non-operative management is ineffective at stabilising the knee or if your aspirations are to return to a very high level of sport, your treating doctor may recommend an ACL reconstruction.  This involves recreating your ACL with a donor graft placed across your knee in an anatomical position to replicate the function previously carried out by your ACL.  There are many graft options including hamstrings, quadriceps tendon, patellar tendon and allograft tendons.  This procedure may sometimes be augmented with an internal brace or lateral extra-articular procedure to further enhance the stability of your knee.  It is advisable to have a full discussion with your treating surgeon as to the best choice of graft and procedure combination for your knee.