The fundamental basis for knee trauma prevention research is that injuries occur in patterns reflecting the underlying causes. Understanding the underlying causes or risk factors for one of the more severe sport-related knee injuries, an anterior cruciate ligament (ACL) disruption, is important for developing intervention strategies, identifying those at increased risk of this injury, and allowing targeted interventions. The risk factors for ACL injury have been considered either internal or external to an individual. In the following review, we focus on what is known about 2 categories of internal risk factors: an athlete's anatomy and menstrual cycle phase
