Patellofemoral pain syndrome (PFPS) is the most common injury sustained by runners. In females, abnormal hip and knee mechanics during running, squatting, and step descent have been associated with PFPS. While the mechanics of PFPS in female runners have been studied extensively, the mechanics of males with PFPS have not. Additionally, current treatment methods for PFPS have been shown to be ineffective at decreasing the chronicity of PFPS, most likely because the underlying faulty mechanics are not addressed. However, realtime kinematic gait retraining has shown promise at reducing both pain and the abnormal mechanics associated with PFPS in female runners. Unfortunately, realtime kinematic retraining has limited clinical utility as it requires an expensive motion capture system. Therefore, the overall purpose of this dissertation was to contribute to the literature with the aim of improving the evaluation and treatment techniques for PFPS.

The purpose of Aim 1 was to determine if males with PFPS run, squat, and descend steps differently than healthy male controls and females with PFPS. We hypothesized that males with PFPS would move in greater genu varum than male controls and females with PFPS. It was found that males with PFPS indeed move in greater genu varum during running and squatting compared with healthy male controls xviiind females with PFPS. These mechanics were not explained by static alignment of the lower extremity.

In Aim 2 we sought to determine if these differences in mechanics translated into changes in measures of PFJ alignment and cartilage contact during a single leg squat in males with and without PFPS. We hypothesized that during a single leg squat, males with PFPS would demonstrate a more medially aligned patella. It was further hypothesized that this alignment pattern would result in more contact on the medial aspect of the PFJ and an overall decrease in total contact area. While males with PFPS demonstrated a more medially tilted patella in moderate knee flexion, there were no differences in cartilage contact profiles between groups. However, total contact had a moderate reduction at 30 degrees knee flexion, which could contribute to excessive PFJ stress in males with PFPS.

The final aim sought to determine if a simple gait retraining technique, using a full length mirror and treadmill, was effective at reducing abnormal alignment and pain in female runners with PFPS. We hypothesized that females with PFPS would demonstrate a reduction in abnormal running mechanics and pain following gait retraining. We further hypothesized that subjects would transfer these movement skills to the untrained tasks of a single leg squat and step descent. Finally, we hypothesized that all changes in mechanics and pain would persist through 3 months. Following gait retraining, subjects reduced their abnormal proximal mechanics during running and reported a reduction in pain. This new movement skill transferred to the single leg squat and step descent. Interestingly, subjects were able to maintain all changes through 1 month post retraining. However at 3 months post retraining, subjects began to drift towards baseline measures for hip mechanics. Despite this drifting, pain was still reduced at 3 months. Further study is required to determine if subjects continue to drift towards baseline mechanics. If so, periodic retraining sessions may be required.

These studies provide further insight into the mechanics and treatment of PFPS. By recognizing sex differences, sex-specific treatments may now be developed. Further, mirror gait retraining for PFPS may be an effective clinical treatment for PFPS, requiring only a mirror and a treadmill. These retraining approaches may also be applied to other gait-related injuries in future studies resulting in a broader application to the general public.