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.~This observational cohort study will enroll 4,800 cadets at the three large U.S. military academies; approximately 50% of those enrolled will be women. Only incoming cadets at the U.S. Naval, Air Force, or Military Academies will be able to participate. Each study participant will undergo a baseline assessment that will include measurement of neuromuscular risk factors using motion analysis, strength testing, and standardized assessment of poor jump-landing technique using the Landing Error Score System (LESS). All participants will be followed for up to 4 years. ACL injuries will be prospectively identified; an injury questionnaire is administered to participants who sustain an ACL injury while they are cadets. Otherwise, there is no further contact.
The anterior cruciate ligament (ACL) is located inside the knee joint and provides stability to the knee. ACL injuries occur more frequently in women than men; the reason for this is unknown. The purpose of this study is to determine gender-specific anatomical, hormonal, and demographic risk factors for ACL injury. This observational cohort study will only enroll incoming cadets at the U.S. Naval, Air Force, or Military Academies.~Study hypothesis: Human movement factors, including key kinetics and kinematics of the knee during a jump-landing task, are associated with the rate of ACL injury.