The ACL stabilizes the knee joint by preventing the shinbone (tibia) from sliding forward beneath the thighbone (femur). A hard twist or excessive pressure on the ACL can tear or rupture the ligament, resulting in high levels of short-term disability and extensive rehabilitation. Previous data indicate that women who participate in sports or who are otherwise physically active have higher rates of ACL injury than men; the reason for this is unknown. There are four groups of potential risk factors for ACL injury: environmental, anatomical, hormonal, and biomechanical or neuromuscular. In particular, poor technique when landing from a jump (also known as jump-landing) is proposed as a specific neuromuscular risk factor of interest in this study. This study will determine gender-specific anatomical, hormonal, and demographic risk factors for ACL injury, as well as quantify gender-specific differences in jump-landing technique and other neuromuscular risk factors.