Pain Variability and Subjective Function in Individuals With Patellofemoral Pain: A Short Report

Individuals with patellofemoral pain (PFP) experience discomfort during various functional activities. Long-term pain is a common consequence of PFP, yet little is known about daily pain variability. Our study consisted of 25 individuals with PFP who completed the Anterior Knee Pain Scale (AKPS) and recorded their daily pain over 10 days. Pain was evaluated using 2 measures of intensity (baseline pain, 10-day average pain) and 2 measures of variability (mean square of successive differences, probability of acute change). Associations between AKPS and the 4 pain measures were calculated with Pearson correlations. We calculated a linear regression to examine the amount of variance in the AKPS explained by the 4 pain measures. Greater mean square of successive differences values were moderately associated with lesser AKPS scores (r= -0.648, P < .001). Mean square of successive differences and 10-day averaged pain were the strongest predictors of AKPS (R-2 = 0.565, P < .001). Pain variability provided a unique perspective on the pain experience and predicted patient-oriented function in individuals with PFP.