Female Adults with Patellofemoral Pain Are Characterized by Widespread Hyperalgesia, Which Is Not Affected Immediately by Patellofemoral Joint Loading
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Objective. Compare pressure pain thresholds (PPTs) at the knee and a site remote to the knee in female adults with patellofemoral pain (PFP) to pain-free controls before and after a patellofemoral joint (PFJ) loading protocol designed to aggravate symptoms. Design. Cross-sectional study Setting. Participants were recruited via advertisements in fitness centers, public places for physical activity and universities. Subjects. Thirty-eight females with patellofemoral pain, and 33 female pain-free controls. Methods. All participant performed a novel PFJ loading protocol involving stair negotiation with an extra load equivalent 35% of body mass. PPTs and current knee pain (measured on a visual analogue scale) was assessed before and after the loading protocol. PPTs were measured at four sites around the knee and one remote site on the upper contralateral limb. Results. Females with PFP demonstrated significantly lower PPTs locally and remote to the knee, both before and after the PFJ loading protocol when compared to control group. Following the loading protocol, PPTs at knee were significantly reduced by 0.54 kgf (95% CI = 0.33; 0.74) for quadriceps tendon, 0.38 kgf (95% CI = 0.14; 0.63) for medial patella, and 0.44 kgf (95% CI = 0.18; 0.69) for lateral patella. No significant change in PPT remote to the knee was observed -0.10 kgf (95% CI = -0.04; 0.24). Conclusions. Female adults with PFP have local and widespread hyperalgesia compared to pain free controls. A novel loading protocol designed to aggravate symptoms, lowers the PPTs locally at the knee but has no effect on PPT on the upper contralateral limb. This suggests widespread hyperalgesia is not affected by acute symptom aggravation.