The Anterior Cruciate Ligament (ACL) of the knee is located within the joint capsule, originating from the femur (thigh bone) and attaching onto the tibia (shin bone). Functionally it is one of the most important structures within the knee joint as it is crucial for providing stability during weight-bearing.
The term ‘anterior’ highlights the primary role of the ACL, which is to prevent forward movement of the tibia in relation to the femur. It is also important for stabilising the knee during pivoting movements.
ACL injuries usually occur in sports involving twisting, pivoting and sudden deceleration, such as football, netball and gymnastics, and are more common in female athletes. It is uncommon for an ACL tear to occur in isolation – due to the mechanism of injury, associated meniscal tears, medial ligament tears or articular cartilage injuries may occur at the same time. Most ACL tears are sustained by:
Hyperextension of the knee on a fixed foot – e.g. an athlete landing from a jump.
Rotation or pivoting manoeuvres – e.g. rapidly changing direction during running (side-stepping or cutting).
Some clinical features of an ACL tear include hearing an audible ‘crack’ or ‘pop’ at the time of injury and an inability to continue participating in sport, immediate pain, swelling, and the sensation of the knee “giving way” during daily activities.
In the 12 months following an ACL tear, progressive rehabilitation in Physiotherapy is essential and must directly focus on regaining function, strength, proprioception, neuromuscular control and sport-specific physical fitness. This will determine both the risk of re-injury and whether surgery is needed to repair the ligament. Current evidence suggests that 40% of people who tear their ACL will cope without surgery, but for those wishing to return to sports involving running, pivoting and change of direction, surgery may be required.
It is absolutely possible to return to sport following an ACL tear (or reconstruction) but it is strictly determined by time and function. Most evidence suggests undergoing intensive Physiotherapy for a period of 9-12 months before returning to sport gives an athlete the greatest potential to succeed without re-injury. A recent study by Grindem et al (2016) showed that for every month return to sport was delayed, the risk of re-injury was reduced by 51% per month up to 9 months. Functional rehabilitation is undoubtedly the most important aspect of achieving safe return to sport, so see your Physiotherapist as soon as possible to give yourself the best outcome!