Prospective Evidence for a Hip Etiology in Patellofemoral Pain.

    Patellofemoral Pain Syndrome has been a topic of debate for some time now.  With limited diagnostic evidence, clinicians don't have much to go off of for definitively ruling in PFP.  More often than not, clinicians use a long subjective history and ruling out other pathologies to aid in their diagnosis of PFP.

    PFP has two primary contributors: increased reaction force and decreased contact area.  Goodfellow & Hungerford ('76) described the PFP mechanism as: patellar malalignment----reduced contact area/uneven distribution of PFJRF----increased PFJ stress/articular cartilage degeneration-----subchondral bone subjected to abnormal stress.

    Fulkerson (2002) described the assumed relationships of PFP mechanism.  The 6 structures that were possible pain generators: subchondral bone, retinaculum, synovial lining, muscle, nerve, skin.  In 1976, subchondral bone was considered the main source of pain, and in 2002 it was still considered the primary source of pain.  
The hypotheses of biomechanical reasons for PFP consider both structural malalignment (ex: femoral anterversion) and dynamic malalignment.   There are two theories for the dynamic malalignment. 
Theory 1: Patella moving within trochlear groove.  The potential lateral displacement and/or tilt of the patella especially during terminal extension and therefore pain is potentially generated by inappropriate tracking during functional movements. Theory 2:  Femoral movement under the patella--tibiofemoral rotation (transverse plane) (Power 2003, Lee 2003, Wilson & Davis 2008, Bolga 2008, Souza 2009).

    All of this brings up the question of whether certain running mechanics can contribute to PFP.  This study prospectively looks at female runners for 2 years, tracking them for injuries after studying their gait.  The results of the study confirmed significant hip adduction was found in those who developed PFP.  Hip internal rotation angle and rearfoot eversion were not found to be significantly different.  What we can take away from this study is that those who develop PFP can have altered hip neuromuscular mechanics and therefore we need to consciously work on correcting that during treatment or before injury.  

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