The Role of Quadriceps Contraction in Patellar Repositioning - a Computed Tomography Study

Background Previous studies have a great discrepancy concerning the effects of quadriceps contraction on patellar lateral displacement and tilt in patients with patellofemoral pain syndrome. This discrepancy may be caused by lack of information regarding to classifications of patellofemoral alignment under quadriceps relaxed. We hypothesized quadriceps contraction has different effects on each type of patellofemoral malalignment.

Methods The investigators expect to recruit 150 subjects with patellofemoral pain syndrome to participate in this study. All patients underwent computed tomography imaging of symptomatic knees, with and without quadriceps muscle contraction in 0°, 15° and 30° of knee flexion. Patellar lateral condyle index and patellar tilt angles of Sasaki and modified Fulkerson were measured to investigate the effect of quadriceps contraction on patellar repositioning.