WHAT IS AN ACL? Ligaments are strong bands of tissue that connect one bone to another. The ACL is one of two ligaments that cross in the middle of the knee, connecting your thighbone (femur) to your shinbone (tibia) and helps to stabilise the knee joint. WHAT ARE THE TYPICAL CAUSES OF AN ACL INJURY? It is estimated that 70 percent of ACL injuries occur without any contact from another player while 30 percent result from direct contact. Typical ways to injure the ACL are:
- Suddenly slowing down and changing direction (cutting or stepping)
- Pivoting with your foot firmly planted on the ground
- Landing from a jump incorrectly
- Stopping suddenly
- Receiving a direct blow to the knee or collision, such as a tackle
When the ligament is damaged, there is usually a complete tear across the tissue. Occasionally partial tears occur or a mild injury may overextend the ligament but leave it intact. WHAT ARE THE SIGNS AND SYMPTOMS OF AN ACL INJURY? Most athletes who experience a full tear of the ACL describe a loud sound such as a ‘pop’ or ‘crack’. This is often followed by a few minutes of extreme pain. A torn ACL is often accompanied by haemarthrosis (bleeding into the joint space) which is seen as a large tense swelling of the knee. Examination of the knee is more easily done within the first hour following the injury before the development of haemarthrosis. Presenting for medical assessment as soon as possible after injury is recommended even if significant swelling has occurred. Athletes with a torn ACL often have severe restriction of movement, particularly when straightening the knee. Other knee injuries such as damage to the meniscus (knee cartilage), and the medial or lateral collateral ligaments may also accompany a torn ACL. PROGNOSIS The natural history of an ACL injury varies from person to person and depends on their activity level, degree of injury and instability symptoms. Complete ACL ruptures usually require surgery as people are generally unable to participate in sports or activities which require changing direction, while others have instability even on normal activities, such as walking. The ACL when torn does not heal itself due to a damaged blood supply therefore surgery is nearly always required. SURGERY To repair a full rupture of the ACL it has to be surgically reconstructed using a graft to replace the torn ligament. The graft is usually taken from the hamstring tendons. Other options include patellar tendon and occasionally a synthetic graft referred to as a LARS procedure. Rehabilitation for a reconstructed ACL is conducted under the direction of an orthopaedic surgeon and the supervision of a physiotherapist. Rehabilitation usually takes between six and nine months.
