Treatment - How can I help

Anterior Cruciate Ligament (ACL) Injury

Other popular names

Who does it affect?

All people, but particularly those engaged in sporting activities.

Why does it happen?

The anterior cruciate ligament (ACL) is one of the main restraining ligaments of the knee.  It runs through the centre of the knee from the back of the femur (thigh bone) to the front of the tibia (shin bone).  The main role of the ACL is in controlling stability of the knee during rotational movements such as twisting, turning or side-stepping.

The ACL is one of the most commonly injured knee ligaments. Sports involving running, jumping and landing pose the most potential for injury and an ACL injury is a very common injury in football or other field or racket sports when trying to change direction rapidly or landing awkwardly from a jump, when twisting onto the bent knee. 

It is a very common skiing injury often being injured when the knee is twisted as a binding fails to release.

A popping sensation (or even a popping noise!) is often experienced at the time of injury and the entire knee tends to swell within a few hours or even a few minutes as the ruptured ligament bleeds inside the knee.  The knee can become markedly swollen and painful and it is usually impossible to continue with the game or activity in which the injury occurred.


When the ACL is ruptured (torn) completely, as occurs most frequently, it does not heal effectively and is either absent or is markedly slack.  As a result the knee has abnormal movement and tends to feel unstable or actually gives way when changing direction or performing pivoting/twisting manoeuvres.

Each time the knee gives way, it can cause pain and swelling that interferes with activities.  It will also result in cumulative damage to the articular cartilage (the cartilage covering the ends of the femur and tibia) and can cause tears of the meniscal cartilages.

In addition to painful episodes of giving way preventing return to sports, meniscal tears and continued damage to the articular cartilage lead to the development of wear and tear arthritis (osteoarthritis).


A ruptured or torn ACL can normally be diagnosed from the knowledge of an accident and understanding of the mechanism of injury and ongoing symptoms. This is ratified by specific tests during your clinical examination.

In some cases, particularly when the knee is very painful and swollen preventing a full examination it may be necessary to carry out an MRI Scan.

Non-surgical treatment

Physiotherapy exercises aimed at strengthening and improving the coordination of the hamstring and quadriceps (thigh) muscles can help the muscles around the knee to help to improve the knee’s stability.

The use of a knee brace can also help reduce instability symptoms experienced from an ACL deficient knee.

Many patients who do not wish to return to sports that involve twisting/turning or sudden acceleration /deceleration manoeuvres find that these measures reduce their instability symptoms so that they do not need further treatment.

However patients who do wish to return to these sports, or who live very physically active lives will normally benefit from surgical reconstruction of their torn ACL.

Surgical treatment

ACL reconstruction surgery involves a general or spinal anaesthetic as a day case or overnight stay.

The procedure is usually performed arthroscopically (through keyhole surgery) and is aimed at replacing the deficient ACL with a graft ligament to stabilise the knee.

Most ACL reconstruction procedures  use the medial hamstring tendons (gracilis and semitendinosus tendons) as the graft to replace the torn ligament. Occasionally it is necessary to use the middle third of patella tendon (the tendon just below the kneecap, taken with a small piece of bone from the patella and the tibia).

The hamstring graft is harvested through a small incision (approximately 3 to 5cm) below the knee over the inner (medial) aspect of the shin.

The graft is inserted through drill holes in the femur and tibia so that it lies in the same position as the original ACL. The graft is then held with screws or similar devices that do not require removal.

Post-surgery rehabilitation

Most patients are able to return home on the same day as surgery or the following day.  All patients will need someone to take them home and be with them on the night following surgery.

The anaesthetic will wear off after approximately 6 hours.  Simple analgesia (pain killers) usually controls the pain and should be started before the anaesthetic has worn off. 

Patients need to use crutches for the first 2 weeks following surgery although they can fully weight-bear - the crutches are mainly to prevent falls until good muscle control has been regained to the leg.


The large bandage around the knee is normally removed 24-48 hours after surgery and a tubigrip may then be used to supply gentle compression to reduce post-operative swelling.

The sterile dressings on the wounds may be replaced with clean waterproof dressings .

The larger incision over the site of the hamstring tendon harvest site is closed using dissolving stitches and the paper butterfly sutures overlying this can be peeled away easily after 10 days.

Return to normal routine

Bathing and showering

The wounds should be kept clean and dry until the wound has sealed. Showering is fine and the waterproof dressings can be changed afterwards. Bathing is best avoided until the wounds are sealed, typically 10 days after surgery.

In summary, whilst the wounds are wet - keep them dry and when the wounds are dry, you can get them wet!


Surgery is followed by a prolonged course of physiotherapy. This requires a commitment to undertake this rehabilitation in order to achieve the best possible result (at least half an hour per day for 6 months).  It is vitally important to stay within the post-operative activity restrictions an physiotherapy guidelines to avoid damaging stretching your reconstructed ligament.

Return to work

The timing of your return to work depends on the type of work and your access, however, the following is a general guide:


When you can walk without crutches or a limp and be in control of your vehicle (about 4-6 weeks).


ACL reconstruction is an extremely safe and reliable operation. However there is a risk of problems or complications with any surgery.

These risks include:

All these risks are uncommon and in total, the chance of you or your knee being worse off in the long term is about or less than 1%.

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