What is the ACL?

The ACL is one of the four main ligaments around the knee. It is located in the middle of the knee and lies in front of the posterior cruciate ligament (PCL). It helps to stabilise the knee, particularly with regards to rotational movements and preventing the knee from slipping forwards on the femur (thigh bone).

How is it injured?

It is commonly injured during sport, often when twisting or turning on the leg, but can be injured during any activity. Patients who injure their ACL often describe hearing a ‘pop’ in the knee and a sensation of the knee ‘jumping’ out of place. Typically the knee will swell straight away and be difficult to walk on.

What problems might arise when the ACL is damaged?

Sometimes there may be no symptoms at all after the initial injury has settled. This could be because it was not an ACL injury, or, possibly it was only a partial tear of the ligament. Most patients find walking on the flat and in a straight line comfortable. However symptoms tend to arise when twisting on the knee, walking on uneven ground or returning to rotational activities and sports. Patients typically complain of a lack of confidence in the knee, a sensation of the knee giving way, or episodes where the knee collapses.

How can it be diagnosed?

The knee should be assessed early on by a specialist surgeon, to diagnose any injury that has been sustained. This will include taking a detailed history, a clinical examination of the knee and usually a MRI scan to ascertain the extent of any damage.

How can it be treated?

The initial treatment following a suspected ACL injury is to protect the knee from further injury and allow the surrounding soft tissues to settle. Often this may require a combination of treatments including RICE (rest / ice / compression / elevation) and crutches to protect the weight through the knee. Physiotherapy can help restore movement to the joint and strengthen the muscles around the knee. For some less active patients, physiotherapy is the only treatment required. In others, a knee brace to help provide stability for specific activities may give adequate support to the knee. Most patients with knee instability symptoms who wish to return to sporting activities will require ACL reconstruction surgery.

How is the ACL reconstructed?

The ACL is reconstructed with keyhole surgery requiring only small incisions around the knee. Tendons from the back of the thigh (hamstrings) are removed to provide the new graft to reconstruct the ACL. The knee is then examined by arthroscopy to address any other damage, before tunnels are made in the bones to thread the ligament through. The new ACL is secured in place by a metal button that sits on the outside of the thigh bone, and a screw that holds it in place in the shin bone.

How long is the recovery?

The surgery is undertaken as a day case and strong pain killing medication is provided to ensure you remain comfortable when back at home. The initial recovery is directed at reducing swelling from the operation, restoring movement back to the knee and strengthening the muscles. Your rehabilitation is guided by the physiotherapist ,who will progress your activities as your knee function returns. For most patients this will take at least 6 months.

Are there any risks?

ACL reconstruction is a minor surgical procedure and so therefore the risks are low. There is however a small risk of developing infection in the knee, bleeding, joint stiffness, damage of the nerves around the knee and residual pain after the operation. There is a risk of on-going instability in the knee as well as a possibility of re-rupturing the ligament in the future. Fortunately the risk of developing leg clots or more life threatening conditions is very rare. The procedure will be discussed with you during your appointment.

Anterior Cruciate Ligament (ACL) Reconstruction