The Anterior Cruciate Ligament (ACL) is a tough band of tissue joining the thigh bone (femur) to the shin bone (tibia) at the knee joint. It runs inside the knee and gives the knee joint stability by controlling the backward and forward movements of the knee and lower leg. ACL stops the tibia bone from moving forwards in front of the femur.  ACL injuries are the most common knee joint injury type and can occur during sports such as Football, Basketball, Volleyball and Tennis (accounts for around 40% of all sports injuries). Knee ligament injuries can be unpredictable and can affect anyone, including fit people who do a lot of sport.

You can tear your Anterior Cruciate Ligament (ACL) if your lower leg extends forwards too much (Picture 1) and it can also be torn if your knee and lower leg are twisted (Picture 2). Common causes of an ACL injury include; landing incorrectly from a jump, stopping suddenly, changing direction suddenly or having a collision, such as during a football tackle. If the ACL is torn, your knee will become very unstable and lose its full range of movement. This can make it difficult to perform certain movements, such as turning on the spot. Some sports may be impossible to play.