Predictors of patellar alignment during weight bearing: an examination of patellar height and trochlear geometry.

Background: Patellar malalignment is thought to be an etiological factor with respect to the development of patellofemoral pain. Although previous studies have suggested that the geometry of the femoral trochlea and the height of the patella play an important role in determining patellar alignment, no investigation has systematically examined these relationships during weight bearing. The aim of this study was to determine whether patellar height and/or trochlear geometry predicts patellar alignment (lateral patellar displacement and lateral patellar tilt) during weight bearing. Methods: MR images of the patellofemoral joint were acquired from 36 participants during weight bearing (25% of body weight) at 4 knee flexion angles (0 degrees, 20 degrees, 40 degrees and 60 degrees). Using the axial images, patellar alignment (lateral displacement and tilt) and femoral trochlear geometry (sulcus angle and inclination of the lateral femoral trochlea) were measured. Patellar height (Insall-Salvati ratio) was measured on reconstructed sagittal plane images. Results: Stepwise regression analysis revealed that at 0 degrees of knee flexion, the height of the patella was the best predictor of lateral patellar tilt while the lateral trochlea inclination angle was the best predictor of lateral patellar displacement. Lateral trochlear inclination was the best predictor of patellar lateral displacement and tilt at 20 degrees, 40 degrees and 60 degrees of knee flexion. Conclusion: Similar to a previous study performed under non-weight bearing condition, our findings suggest that lateral trochlear inclination is an important determinant of patellar alignment in weight bearing. Level of Evidence: Level III (C) 2013 Elsevier B.V. All rights reserved.