An anterior cruciate ligament injury is extreme stretching or tearing of the anterior cruciate ligament (ACL) in the knee. A tear may be partial or complete. Ligaments are strong bands of tissue that attach one bone to another. The ACL connects the thighbone to the shin bone, crossing the knee. For an unknown reason, women are more susceptible to ACL injuries. ACL tears may be caused by contact or non-contact injuries. A blow to the side of the knee, like during a football tackle, may result in an ACL tear. However, coming to a quick stop, combined with a direction change while running, pivoting, landing from a jump, or overextending the knee joint, can cause injury to the ACL. Sports like basketball, football, soccer, and skiing have regular occurrences of ACL tears.