The relatively high risk of noncontact anterior cruciate ligament (ACL) rupture among female athletes has been a major impetus for investigation into the etiology of this injury. A number of risk factors have been identified, both internal and external to the athlete, including neuromuscular, anatomical, hormonal, shoe-surface interaction, and environmental, such as weather. The anatomic and neuromuscular risk factors, often gender related, are the focus of most ACL injury prevention programs. Although studies have shown that biomechanic- centered prevention programs can reduce the risk of ACL injury, many questions remain unanswered. More research is needed to increase our understanding of the risk factors for ACL injury; how injury prevention programs work and can the clinical application of such programs be optimized.