OBJECTIVE: Exercise has beneficial effects on pain in knee osteoarthritis (OA), yet the underlying mechanisms are unclear. The purpose of this study was to investigate the effects of exercise on pressure-pain sensitivity in patients with knee OA.

METHODS: In a randomized controlled trial, participants were assigned to 12 weeks of supervised exercise therapy (ET; 36 sessions) or a no attention control group (CG). Pressure-pain sensitivity was assessed by cuff pressure algometry on the calf of the most symptomatic leg. The coprimary outcomes were pressure-pain thresholds (PPTs) and cumulated visual analog scale pain scores during constant pressure for 6 minutes at 125% of the PPT as a measure of temporal summation (TS) of pressure-pain. Secondary outcomes included self-reported pain using the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire. Analyses were based on the "per-protocol" population (participants following the protocol).

RESULTS: Sixty participants were randomized (31 in ET group, 29 in CG), and the per-protocol population included 48 participants (25 in ET group, 23 in CG). At followup, mean group differences in the change from baseline were 3.1 kPa (95% confidence interval [95% CI] 0.2, 6.0; P = 0.038) for the PPT, 2,608 mm × seconds (95% CI 458, 4,758; P = 0.019) for TS, and 6.8 points (95% CI 1.2, 12.4; P = 0.018) for KOOS pain, all in favor of ET.

CONCLUSION: Pressure-pain sensitivity, TS, and self-reported pain are reduced among patients completing a 12-week supervised exercise program compared to a no attention CG. These results demonstrate beneficial effects of exercise on basic pain mechanisms and further exploration may provide a basis for optimized treatment.