Biomechanical factors associated with patellofemoral pain syndrome in runners

This study was aimed at examining functional variables that were hypothesized to be related to the onset of Patellofemoral Pain Syndrome (PFPS) in runners. These variables included maximal tibial rotation with respect to the foot ($\Delta\rho\sb\max$), maximal tibial rotation with respect to the femur ($\Delta\psi\sb\max$), maximal patellofemoral joint contact force $\rm(F\sb{PF\max})$, Quadriceps-angle (Q-angle), and weekly training distance. Three groups of runners participated in a 3-dimensional kinematic and kinetic evaluation of their running styles. These groups included an asymptomatic group, a group experiencing PFPS and a group who had experienced PFPS in the past with no pain at the time of the study. The third group was added to the study to control for any changes in biomechanics which may be due to pain.

The analysis was divided into a group comparison and a comparison of individual results. Group comparisons performed using a multivariate ANOVA revealed that no variables were different across the groups ($\alpha$ = 0.05). A Discriminant Function Analysis revealed maximal tibial rotation with respect to the femur $(\psi\sb\max)$ was the only variable to have predictive capabilities, properly classifying 54.7% of all cases. Since PFPS is a multifactorial problem, individual subject results were able to show which variables may have been responsible for the onset of PFPS. The most frequent combination of factors for people with PFPS was a high Q-angle and a high maximal tibial rotation with respect to the femur.