Radiographic measures in subjects who are asymptomatic and subjects with patellofemoral pain syndrome

Lateral tilt and displacement of the patella are considered characteristic features of patellofemoral pain syndrome. It has been suggested that abnormal patellar tilt and displacement are detected best with the knee near full extension, which requires computed tomography or magnetic resonance imaging. The objective of the current study was to determine whether alignment abnormalities could be detected in subjects with patellofemoral pain syndrome from axial radiographs obtained at 35degrees knee flexion using a new, standardized radiographic technique. Thirty-three subjects with patellofemoral pain syndrome and 33 matched control subjects were recruited from a military population. Lateral and axial (unloaded and with quadriceps contraction) radiographs were taken using the Patellofemoral QUESTOR(TM) Precision Radiograph system. Measures of patellar tilt and displacement, and anatomic measures (sulcus angle, patellar facet angle, patella alta) were obtained from the radiographs. No significant differences in patellar tilt or displacement were detected between the groups (paired t tests) in either the unloaded or loaded (quadriceps contracted) condition, suggesting that these measures, obtained at this knee angle are not useful diagnostic or outcome measures in patellofemoral pain syndrome. Patellar angle, sulcus angle, and patellar height also did not differ between groups suggesting that these are not etiologic factors in patellofemoral pain syndrome.