Anterior cruciate ligament reconstruction (ACL reconstruction) is a surgical tissue graft replacement of the anterior cruciate ligament, located in the knee, to restore its function after anterior cruciate ligament injury. The torn ligament is removed from the knee before the graft is inserted. The surgery is performed arthroscopically. The ACL is a strong ligament that runs diagonally through the middle of your knee. It helps to keep your knee stable, especially when you turn, or when your knee joint moves from side to side. The ACL is one of the most commonly injured ligaments. It s usually torn when you slow down very quickly while turning or sidestepping at the same time. You are more likely to injure your ACL if you play sport, particularly basketball, netball, rugby or football, or if you ski. ACL reconstruction involves replacing your torn ligament with a graft. The graft is usually taken from a tendon in another part of your knee, for example, your hamstring or patella tendon. But sometimes it can be a graft from a donor. This is called an allograft. Your surgeon will discuss the different graft options with you. ACL reconstruction is carried out to try to make your knee stable. This means that you may be able to return to playing sport. However, it will depend on whether there are other problems with your knee, such as torn cartilages, other ligament injuries or arthritis.