Effect of Restricted Hip Flexors on Biomechanical Risk Factors for ACL Injury

Anterior Cruciate Ligament injuries are devastating on patients and society. It has been theorized that hip flexor restriction may affect muscles distally in the kinetic chain with no supporting literature. We hypothesized that those with hip flexor restriction will display biomechanics linked to ACL injury. Forty subjects completed functional tasks, range of motion measurements, and strength testing of gluteal muscles. Independent t-tests were run to determine the difference between control subjects and those with restricted hip flexors. Subjects with restricted hip flexors were observed to have less dorsiflexion, and less hip abduction and external rotation. There were no differences in gluteal strength. Restricted subjects were observed to have less anterior pelvic tilt at rest, less gluteus maximus activation during squatting, and exhibited differences in kinematics and kinetics during functional tasks. This indicates hip flexor restriction may lead to biomechanics identified as risk factors for ACL injury, and warrants further examination.