Anterior cruciate ligament injury is when the anterior cruciate ligament (ACL) is either stretched, partially torn, or completely torn.[1] The most common injury is a complete tear.[1] Symptoms include pain, a popping sound during injury, instability of the knee, and joint swelling.[1] Swelling generally appears within a couple of hours.[2] In approximately 50% of cases, other structures of the knee such as surrounding ligaments, cartilage, or meniscus are damaged.[1]