Damage to the Anterior Cruciate Ligament (ACL)

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What is the ACL?

The ACL is an important ligament in the centre of the knee. It is one of several ligaments that keep the knee in joint and stable. When it is injured, the motion of the knee can become abnormal so that it collapses (gives way) on some movements. The ligament also contains nerves that tell your brain where your knee is. After injury these stop working and cause a feeling of instability. Various terms may be used to describe the injury such as, snapped, ruptured or stretched, but basically the ligament is either completely torn or, where strands are still intact, partially torn.

Why did it rupture?
The knee injury does not have to be particularly violent; it is a matter of the knee being in an awkward position at the time. Some people may have changes in the knee making them prone to this injury.

Is it a common injury?
Yes. As more people are taking part in sports activities, the injury has become more common. Football, rugby, skiing and netball are the usual causes. However, it can occur in any sport, even with a simple stumble.

How can you tell if my ACL is damaged?
It is possible to make a diagnosis from the history of the event as to what happened at the time of injury, the trouble you have had since and from examining your knee. It may be necessary to perform x rays, scan your knee with an MRI scan or examine it under anaesthetic and potentially even inspect inside it with an arthroscopy (key hole surgery).

Is my ACL completely ruptured?
This can be difficult to tell in the early stages. Your surgeon or physiotherapist will explain the details of your injury. Whether the ligament is partially or completely ruptured is less important than the function of your knee.

Could anything else be damaged in my knee?

Other ligaments, the cartilage or menisci and the joint surface on the bone can also be damaged. If this has happened the details of the injury will be explained to you.

Could it have been repaired at the time I injured it?
No. The ligament is like a piece of elastic and when it snaps the ends pull apart. It is impossible to stitch it back together and the ends will not heal, even if your leg is put in plaster.

What will happen in the future?
This is difficult to predict. Some people seem to have no trouble at all; some have a feeling of weakness or instability when playing sport and some have repeated giving way during simple day to day activities.

If it is left alone will my knee come to any harm?
Providing your knee does not keep giving way, you are unlikely to get any serious trouble from it. However, there is no doubt that if you have a very unstable knee or continue in sport at a high level, you are at risk of further ligament injury, torn cartilage and a greater chance of developing wear and tear (osteoarthritis) in later life.

What can be done?
There are three options for treatment:
Physiotherapy. With specific advice and exercises, nearly all people with partial rupture and many with complete rupture can manage very well.
Brace. A simple knee support may give more confidence, but to really stabilise the knee a fairly large and complicated brace is needed. This treatment is suitable for those who cannot have surgery or are awaiting an operation. A brace can also be used during recovery from surgery. Due to the possible risk of injury to other players, some sports do not allow a brace. If necessary, the appliance department can give you advice following referral from your surgeon.
Surgery. It is possible to reconstruct the ACL. Several techniques are used. The surgery is quite complicated and full recovery requires a lot of physiotherapy and home exercise. If surgery is being considered, this will be discussed with you by your surgeon. The operations are successful in 95% (19 out of 20) of people, in that you should be able to return to some sport at about 10 – 12 months after the operation. Recent reports that up to 25 – 30 percent of patients who have a reconstruction of their ACL will need a further knee operation within 10 years.

• Surgery usually requires one night in hospital. Crutches are used for 2 – 3 weeks. No driving for six weeks generally and regular follow-up by physiotherapy and surgical team to ensure progress.