Anterior Cruciate Ligament (ACL) Rupture & Reconstruction

ACL Knee Injury & Reconstruction Explained

An Anterior Cruciate Ligament (ACL) tear is a fairly common knee injury in sports that involve changing direction and turning. The ACL lies deep within the knee joint, connecting the thigh bone with the shin bone. The function of the ACL is to prevent excessive forward movement of the shin in relation to the thigh and also to prevent excessive rotation at the knee joint. The ACL plays a major role in maintaining knee joint stability.

An ACL injury can occur in several different ways, most notably by landing from a jump onto a bent knee then twisting, or landing on a knee that is over-extended. In collision sports, direct contact to the knee from opponents can cause an ACL injury. Because of the amount of force that is required to damage the ACL it is not uncommon for other structures within the knee such as the meniscus or medial ligament to also be damaged.

A moderate impact against the inner side of the knee joint causes the Lateral Collateral Ligament to rupture. A more violent impact causes the Anterior Cruciate Ligament to also rupture. In severe cases the Posterior Cruciate Ligament ruptures.

ACL injuries have been reported to occur more often now than ever before, which may be due to the increased intensity of sporting activity. In soccer, it is reported that for every 1000 hours of football (soccer) played (training and matches) there are between 4 and 7 ACL injuries.

ACL Knee Injury Signs & Symptoms

At the moment of injury the person may experience a snapping sensation deep within the knee joint. There will be pain, proportional to the force and degree of damage to other structures within the knee joint. The Medial Collateral Ligament and Menisci (Cartilage) are often damaged together with the ACL.

In some cases, the person may feel able to continue playing but, as soon as the knee is put under strain during sports activity, the knee joint will become unstable.

The reason the person is unable to carry on is that the restraining function of the ACL is absent and there is excessive rotation and forward movement of the shin in relation to the thigh, making the knee joint unstable. After a couple of hours the knee joint will become painfully swollen due to what is called a haemarthrosis (bleeding within the joint). This swelling provides a protective function by not allowing the person to use their knee but, if it persists, it can cause complications during the rehab.

ACL Knee Injury Treatment

During the acute stage of the injury (the first 48-72 hours) exact diagnosis is very difficult due to the gross swelling around the joint. The initial goals of physiotherapy treatment are to reduce knee pain and knee swelling. Ice packs can be applied for periods of twenty minutes every couple of hours (never apply ice directly to the skin as it can cause an ice burn) to relieve pain and reduce bleeding within the tissue.

Once the initial treatment for the swollen knee has taken effect, the clinical diagnosis may be possible. This may be achieved by a physio performing stress tests on the knee ligaments - the degree of laxity within the joint will allow the clinician to estimate the degree of damage. If there is any doubt, or to confirm the clinical tests, the patient is sent for further investigations. Most commonly an MRI scan is used to ascertain the level of knee injury. In some cases the MRI scan may not give a clear picture of the damage and it may be necessary to survey the joint with an arthroscope. The combination of these findings allows the orthopaedic consultant to build a picture of the extent of the damage.

The treatment of the ACL injury is dependent upon the amount of damage and the subsequent functional impairment, the age of the patient and the level of sporting activity. If the diagnostic investigations reveal only a partial tear of some of the fibres of the ACL, and there is minimal instability, then a conservative approach with a physiotherapist and knee brace is usually indicated. This option is also more likely for more sedentary individuals. In the case of individuals who are involved in a high level of sport where a degree of instability is functionally unacceptable, then ACL reconstruction knee surgery is the surest way to restore normal function.

A knee brace can restore a degree of knee joint stability, preventing the feeling that the knee is going to ‘give way'. Together with physiotherapy treatment, a knee brace can be perfectly sufficient in less active individuals. A knee brace is also helpful in more active individuals, who decide to have ACL reconstruction knee surgery. Modern knee braces provide stability without compromising knee movement, so can be used during rehabilitation and on return to sporting activities.

ACL reconstruction knee surgery has evolved beyond recognition since the first ACL repair in 1963. Development has continued since then and the latest surgical technique uses a strip of the patella tendon from the patient's knee or a strip of the patient's hamstring tendon as a graft to replace the ACL. In addition to advances in the surgical procedure, there have been advances in post-operative rehabilitation that have seen a return to sports activity, in most cases, in less than six months.

Your local IPA physiotherapist will be able to provide you with an outline of the post-operative rehabilitation process, and give you an approximate time to resume your normal functional activity. Simply phone 1300 PHYSIO to be transferred directly to their practice.

ACL Knee Injury Prevention

Research by Dr Donald Shelbourne, the world expert on ACL injury, has shown that there is a relationship between the size of the ACL and injury. Specifically, if you have a small ACL then you are more likely to suffer an ACL injury. Obviously you can't do much about the size of your ACLs, we'd recommend proprioception training (balance and limb/joint awareness) using a wobble board, as well as avoiding sport when you are in a fatigued state as this can increase the risk of injury.