ACL Tear

Anterior cruciate ligament (ACL) injuries

The ACL is one of the main stabilising ligaments of the knee joint. It 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 knee can give way when twisting or changing direction. If this instability is not treated, further damage can be done to other structures within the knee, such as the articular (end of bone) or meniscus (between the bones) cartilages.

Why does it occur?

The ACL can be torn when the knee is twisted or hyperextended suddenly, often during sport sporting activities such as football or netball. It is also a common skiing accident injury. 

What are the symptoms?

When someone tears an ACL, they often hear or feel a pop in the knee, followed by pain and swelling of the joint, stopping them from continuing with the physical activity. Often those who have torn their ACL will limp because of the pain and  restricted range of movement.

With rehabilitation, 20 to 30 per cent of those 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, without treatment, will have some ongoing symptoms, such as knee instability, the knee 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 the 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 surgeon to rule out any potential other injuries to the bone or cartilage.

How is it treated?

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.

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 surgeon may recommend an ACL reconstruction. This involves recreating your ACL with a donor graft, placed across your knee, to replicate the function of the damaged ligament. There are many tendon graft options, including hamstrings, quadriceps, patellar and allograft (transplanted from a donor). This procedure may sometimes be augmented with an internal brace or an extra procedure to further enhance the stability of your knee. It is advisable to have a full discussion with your surgeon as to the best choice of graft and procedure combination for your knee.

Treatment options

ACL reconstruction


Knee arthroscopy


Non-surgical treatment

The One Orthopaedics team specialists

Mike Lemon

Consultant Orthopaedic Surgeon FRCS (Tr&Orth), Knee and Hip

Oliver Templeton-Ward

Consultant Orthopaedic Surgeon FRCS (Tr&Orth), Knee

Kerry Acton

Consultant Orthopaedic Surgeon FRCS (Tr&Orth), Hip and Knee