An ACL (anterior cruciate ligament) damage happens when the ACL—the tissue bands that connect your knee bones—stretches or rips. ACL injuries are common in sports, particularly when athletes make abrupt stops, fast spins, or land awkwardly. Other factors also may play a role in whether you suffer an ACL injury. For example, if an athlete is more prone to ACL tears, they may suffer more often or later in their career because of this risk factor. The most common site for an ACL tear is at its junction with the tibia (shin). However, it can happen at any point where the ligament crosses from one bone to another. These points include the anterior side where it connects with the top of the femur (thigh), as well as the posterior side where it attaches to the bottom of the tibia. A tear can also occur between these two points. Other muscles and tissues around the knee may be injured in conjunction with an ACL rupture. These other injuries include meniscus tears and fractures to surrounding bones such as the tibia and fibula. An ACL tear can cause severe pain, instability, and loss of function of the knee. In addition, there is evidence that repeated trauma to the unstable knee may lead to osteoarthritis later in life. There are two types of ACL repairs: replacement surgery and reconstruction.