Pain Variability Predicts Subjective Function in Individuals with Patellofemoral Pain: A Short Report.

Individuals with patellofemoral pain (PFP) experience pain during various functional activities. Long-term pain is a common consequence of PFP, yet little is known about daily pain variability. Twenty-five individuals with PFP completed the Anterior Knee Pain Scale (AKPS) and recorded daily pain over 10-days. Pain was evaluated by two measures of intensity (baseline pain, 10-day average pain) and two measures of variability (mean square of successive differences [MSSD], probability of acute change [PAC]). Associations between AKPS and the four pain measures were calculated with Pearson correlations. A linear regression was performed to examine the amount of variance in the AKPS explained by the four pain measures. Greater MSSD values were moderately associated with lesser AKPS scores (r =-.648, p<.001). MSSD and 10-day averaged pain was the strongest predictor of AKPS (R2=.565, p<.001). Pain variability provides a unique perspective in the pain experience and predicts patient-oriented function in individuals with PFP.