Relation of pain sensitization to self-reported and performance-based measures of physical functioning: the Multicenter Osteoarthritis (MOST) study

Objective: It is unclear if alterations in nociceptive signaling contribute to poor physical functioning in persons with knee osteoarthritis (OA). We aimed to characterize the relation of pain sensitization to physical functioning in persons with or at risk for knee OA, and determine if knee pain severity mediates these relationships.

Materials and methods: We used cross-sectional data from the Multicenter Osteoarthritis Study, a cohort study of persons with or at risk for knee OA. Pressure pain thresholds (PPTs) and temporal summation (TS) were assessed with quantitative sensory testing. Self-reported function was quantified with the Western Ontario and McMaster Universities Arthritis Index function subscale (WOMAC-F). Walking speed was determined during a 20-m walk. Knee extension strength was assessed with dynamometry. Relations of PPTs and TS to functional outcomes were examined with linear regression. The mediating role of knee pain severity was assessed with mediation analyses.

Results: Among 1560 participants (60.5% female, mean age (SD) 67 (8), body mass index (BMI) 30.2 (5.5) kg/m²), lower PPTs and the presence of TS were associated with worse WOMAC-F scores, slower walking speeds, and weaker knee extension. The extent of mediation by knee pain severity was mixed, with the greatest mediation observed for self-report function and only minimally for performance-based function.

Conclusions: Heightened pain sensitivity appears to be meaningfully associated with weaker knee extension in individuals with or at risk for knee OA. Relations to self-reported physical function and walking speed do not seem clinically meaningful. Knee pain severity differentially mediated these relationships.