Recent research suggests that altered patellofemoral joint mechanics may be the result of femur motion as opposed to patella motion. The purpose of this dissertation was to clearly define the role of hip/femur motion in contributing to patellofemoral joint dysfunction. To accomplish this objective, three studies were undertaken.

The purpose of study #1 was to determine whether individuals with patellofemoral pain (PFP) demonstrate abnormal hip kinematics during functional tasks and to determine if such motions could be explained by hip muscle weakness and/or abnormal muscle activation patterns. Results revealed that PFP subjects demonstrated increased hip internal rotation, hip muscle weakness, and increased gluteus maximus EMG when compared to pain-free controls. These findings suggest that subjects with PFP were attempting to recruit a weakened muscle, perhaps in an effort to stabilize the hip joint.

The purpose of study #2 was to determine if hip muscle performance and femoral morphology differ between females with PFP and pain-free controls, and to determine to what degree these measures predict hip internal rotation during running. Females with PFP demonstrated deficits in eight of ten hip strength measurements and increased femoral inclination. Step-wise regression analysis revealed that isotonic hip extension endurance was the only predictor of hip internal rotation.

The purpose of study #3 was to determine if individuals with PFP demonstrate excessive medial femoral rotation and to determine whether femur motion contributes to altered patellofemoral joint kinematics (as opposed to patella motion). Findings revealed that females with PFP demonstrated greater lateral patella displacement & tilt and medial femoral rotation, with no differences in patella rotation. Based on these results it was concluded that altered patellofemoral joint kinematics in persons with PFP appears to be more related to excessive medial femoral rotation as opposed to lateral patella rotation.

A common finding across all studies was the observation of increased internal rotation of the hip/femur in females with PFP. The tendency for the hip to internally rotate was associated with diminished hip muscle performance as opposed to femoral structure. Taken together, these studies suggest that the etiology of patellofemoral joint dysfunction may have a proximal origin.