A clinical and biomechanical profile of female athletes with and without patellofemoral pain

Female athletes may exhibit unique risks and orthopedic presentations when engaging in physical activity. Gender differences have been noted in the incidences of particular knee injuries, with female athletes/runners reported to be two times more likely to present with patellofemoral disorders as their male counterparts. Unfortunately, the etiology of patellofemoral pain (PFP) remains elusive and multifactorial. The purpose of this study was to examine the clinical and biomechanical profiles of female athletes with and without PFP during walking and running to determine if there is a set of variables that differentiates the groups. Forty-three subjects with moderate PFP and forty-five control subjects with no history of PFP participated in one 60 minute testing session. Each participant completed a series of questionnaires and was assessed for height, weight and activity level. A Modified Thomas test, Modified Ober test and straight leg raise assessment were performed bilaterally looking for differences between the right and left limbs. Pelvis and hip range of motion, maximum vertical ground reaction force, contact time, and center of pressure variability (COPx) were measured during 30 second treadmill walk and run trials utilizing a 9-camera motion analysis system and a Pedar insole system. The symmetry index (SI) (Robinson et al., 1987) was used to characterize asymmetry of kinematic and kinetic variables of both groups. Two clinical indices [Tightness Index (TI) and Pelvic Symmetry Index (PSI)] were established based on results of the Modified Thomas and Ober tests. Based on logistic regression results, we found that the TI and PSI clearly differentiated the two groups with the PFP group displaying significantly greater numbers of positive signs within both indices (p<.001). Biomechanical variables did not clearly define the groups, however, there was some evidence that measurement of the mediolateral variability of the COPx/gait line might indicate lower extremity kinetic chain instability as seen at the foot and ankle during activity (p=.07 during walking; p=.013 during running). The results of this study suggest that there is a significant association between the results of the TI and PSI and PFP. Clinically, the tests are quick and easy to perform and may be helpful in distinguishing those at risk for PFP.