Effects of high frequency strengthening on pain sensitivity and function in female runners with chronic patellofemoral pain

Objective: To investigate the effects of a high frequency strengthening program on function, pain, and pain sensitization in female runners with chronic patellofemoral pain (PFP). Design: Cross-sectional study. Setting: University laboratory. Participants: Thirty female runners (mean age 32 ± 8.1 years) with chronic PFP completed an 8-week home strengthening program. Main outcome measures: Variables assessed at baseline, 8-weeks, and 12 weeks included single leg step down test (SLSD), pain, Anterior Knee Pain Scale (AKPS), University of Wisconsin Running Injury and Recovery Index (UWRI), and quantitative sensory testing. Results: There was large and statistically significant improvement at 8 and 12 weeks for average knee pain (η_p² = 0.334, p < 0.001), worst knee pain (η_p² = 0.351, p < 0.001), SLSD (η_p² = 0.161, p = 0.001), AKPS (η_p² = 0.463, p < 0.001), and UWRI (η_p² = 0.366, p < 0.001). A medium to large effect and statistically significant improvement in pressure pain threshold testing was found for all local and remote structures (η_p² range, 0.110 to 0.293, range p < 0.001 to p = 0.009) at 8 and 12 weeks. Conclusions: There was a significant decrease in local and remote hyperalgesia via mechanical and thermal pain sensitivity testing in female runners with chronic PFP. There was a large effect and significant improvement in self-reported pain and function.