The anterior cruciate ligament (ACL) is a tough, flexible band of tissues running through the knee joint. An ACL injury occurs when the anterior cruciate ligament is torn or overstretched. Women are about two to eight times more prone to ACL injuries than men. There are increased cases of ACL injuries among teenagers involved in organized sports and recreational activities. The number one indication of an ACL injury is a popping noise combined with pain and swelling. Symptoms also include grinding sensations of your bones and kneecap and being unable to put weight on your affected leg. Partial tears can be treated at home or with over-the-counter medicine. Other options include bracing and physical therapy, but reconstruction surgery may be best for some complete ACL tears.