An ACL (anterior cruciate ligament) is one of the four major ligaments in the human knee. It is the ligament that is located between the femur and the tibia (two main leg bones) within the knee. It attaches to the back of the femur, runs through the knee and attaches to the front of the tibia. It consists of two bundles of fibers, called anteromedial and the posterolateral. The ACL prevents forward movements of the tibia form underneath the femur. It essentially keeps the leg in line. It is the ACL, along with the PCL (posterior cruciate ligament) that keeps the knee joint stable.
What causes an ACL tear?
An ACL injury or tear is very common in athletes, particularly those that engage in contact sports or sports that require quick directional changes. The ACL is often torn when the knee bends too far backwards or is pushed too far to the side. Most ACL tears are a result of the knee joint twisting or pivoting whilst the foot is firmly planted on the ground. It may also occur after a jump as the knee joint twists when the foot becomes grounded. ACL tears may also be caused by direct, forceful contact to the knee such as that received in a football or rugby tackle.
Some of the sports that are most commonly associated with ACL tears include skiing, American football, Australian rules football, basketball, rugby, martial arts, artistic gymnastics and soccer. Most ACL tears occur when an athlete lands flat on their heels rather than taking the weight on their whole foot or their toes. The force that travels up the tibia into the knee causing the tibia to sharply move either forwards or backwards, taking it out of line with the femur placing undue stress on the anterior cruciate ligament. Older people may also injure their ACL when they slip and fall. This is due to the normal wear and tear on the knee ligaments.
Did you know?
ACL tears are more likely to occur in female athletes who have about a 2- 8% larger chance of an ACL injury. It is unknown why this is so, some research suggests that the female hormone oestrogen has an effect on the anterior cruciate ligament.