The influence of patellofemoral joint loading on patella strain and patella water content in females with patellofemoral pain

2012-11-21Recent research has suggested that patellofemoral pain (PFP) may be the result of elevated loading of highly-innervated subchondral bone during weight-bearing activities. Furthermore, excessive bone strain level resulting from elevated patellofemoral joint stress is believed to cause bone injury, increased bone water content, and patellofemoral symptoms. The purpose of this dissertation was to study potential mechanism(s) of PFP by exploring the influence of patellofemoral joint loading on pain, patella bone strain, and patella water content. To accomplish this objective, 3 studies were undertaken. ❧ The purpose of Chapter III was to determine whether individuals with PFP exhibit elevated patella bone strain magnitudes when compared to pain-free controls. The secondary objective was to determine the influence of patella cartilage thickness on patella strain magnitude. Findings revealed that individuals with PFP demonstrated increased magnitudes of peak and average minimum and maximum principal strain values within the patella. Additionally, decreasing cartilage thickness was associated with higher levels of peak minimum principal strain and peak maximum principal strain. ❧ The purpose of Chapter IV was to compare patella water content between female runners with and without PFP using chemical-shift-encoded water-fat magnetic resonance imaging (MRI). Results indicated that subjects with PFP demonstrated significantly greater total patella water content when compared to pain-free controls. ❧ The purpose of Chapter V was to quantify changes in pain and patella water content following an acute bout of loading in female runners with PFP. Findings revealed that persons with PFP demonstrated significant increases in pain and patella water content immediately following a running protocol. Pain and patella water content decreased to pre-running levels following 48 hours of rest. ❧ The primary finding of this dissertation was that PFP was associated with increases in patella bone strain magnitude and patella water content. The higher resting patella water content observed in female runners with PFP is suggestive of venous engorgement and elevated extracellular fluid due to chronic overloading. Additionally, transient changes in patella water content associated with repetitive impact loading (i.e., running) may contribute to patellofemoral symptoms