A prospective investigation of biomechanical risk factors for patellofemoral pain syndrome: the Joint Undertaking to Monitor and Prevent ACL Injury (JUMP-ACL) cohort.

BACKGROUND Patellofemoral pain syndrome is one of the most common chronic knee injuries; however, little research has been done to determine the risk factors for this injury. HYPOTHESIS Altered lower extremity kinematics and kinetics, decreased strength, and altered postural measurements will be risk factors. STUDY DESIGN Cohort study (prognosis); Level of evidence, 2. METHODS A total of 1597 participants were enrolled in this investigation and prospectively followed from the date of their enrollment (July 2005, July 2006, or July 2007) through January 2008, a maximum of 2.5 years of follow-up. Each participant underwent baseline data collection during their pre-freshman summer at the United States Naval Academy. Baseline data collection included 3-dimensional motion analysis during a jump-landing task, 6 lower extremity isometric strength tests, and postural alignment measurements (navicular drop and Q angle). RESULTS Risk factors for the development of patellofemoral pain syndrome included decreased knee flexion angle, decreased vertical ground-reaction force, and increased hip internal rotation angle during the jump-landing task. Additionally, decreased quadriceps and hamstring strength, increased hip external rotator strength, and increased navicular drop were risk factors for the development of patellofemoral pain syndrome. CONCLUSION Multiple modifiable risk factors for patellofemoral pain syndrome pain have been identified in this investigation. To decrease the incidence of this chronic injury, the risk factors for patellofemoral pain syndrome need to be targeted in injury prevention programs. CLINICAL RELEVANCE Prevention programs should focus on increasing strength of the lower extremity musculature along with instructing proper mechanics during dynamic movements to decrease the incidence of patellofemoral pain syndrome.