Associations between pain sensitization and measures of physical function in people with hand osteoarthritis: Results from the Nor-Hand study

Objective To examine whether pain sensitization is associated with hand and lower extremity function in people with hand osteoarthritis (OA) in the Nor-Hand study. Design Pain sensitization was assessed by pressure pain thresholds (PPTs) and temporal summation (TS). Hand function was assessed by Australian/Canadian Osteoarthritis Hand Index (range: 0-36), grip strength and Moberg pick-up test, and lower extremity function was assessed by Western Ontario and McMaster Universities Osteoarthritis Index (range: 0-68), 30-second chair stand test, and 40-meter walk test. We examined whether sex-standardized PPT and TS values were cross-sectionally associated with measures of physical function using linear regression analyses. Beta coefficients were presented per sex-specific standard deviation of PPT and TS. The mediating effect of pain was examined by causal-inference based mediation analysis. Results In 206 participants, higher PPTs at/near the hand, indicative of less peripheral and/or central pain sensitization, were associated with greater grip strength and better self-reported hand function (beta for PPT at finger joint on AUSCAN function: -1.41, 95% CI -2.40, -0.42). Higher PPTs at/near the hand, near the knee and at trapezius were associated with lower extremity function, although not statistically significant for all outcomes. Self-reported pain severity mediated the effect of PPT on self-reported function. TS was not associated with hand or lower extremity function. Conclusion Peripheral sensitization, and possibly central sensitization, was associated with impaired function. Effects of PPTs on self-reported function were mediated by self-reported pain, whereas there might be a direct effect of sensitization or effects through other mediators on performance-based function.