Enhanced Pain Sensitivity Among Individuals With Symptomatic Knee Osteoarthritis: Potential Sex Differences in Central Sensitization

Abstract

Objective: Symptomatic knee osteoarthritis (OA) is a condition commonly associated with increased pain, disability, and functional limitations. Given the poor correspondence between radiographic evidence and clinical pain, central sensitization has been implicated as a potential mechanism underlying pain facilitation in knee OA. Sex may be a moderator of centrally mediated changes in knee OA pain; however, few studies have systematically assessed this. Therefore, the aim of this study was to examine differences in peripheral and central sensitization in men and women with symptomatic knee OA, as well as to determine whether these differences vary across age (middle age versus older age).

Methods: Participants (n = 288) between the ages of 45 and 85 years completed a battery of quantitative sensory pain procedures assessing sensitivity to contact heat, cold pressor, mechanical pressure, and punctate stimuli. Differences in temporal summation (TS) were examined, as well as measures of clinical pain and functional performance.

Results: When compared to men, women exhibited greater sensitivity to multiple pain modalities (i.e., lower heat, cold, pressure thresholds/tolerances, greater TS of pain); however, there were no sex differences in clinical pain, with the exception of greater widespread pain observed in women. Although there were select age-related differences in pain sensitivity, sex differences in pain varied minimally across the age cohort.

Conclusion: Overall, these findings provide evidence for greater overall sensitivity to experimental pain in women with symptomatic knee OA compared to men, suggesting that enhanced central sensitivity may be an important contributor to pain in this group.

Figure 1

Adjusted means and standard errors for punctate pressure across sex. For punctate pressure at the hand, the main effect of sex was non-significant for the single stimulus and temporal summation (TS). For punctate pressure at the knee, women had higher pain ratings for the single stimulus compared to men, and had greater TS of punctate pressure pain.

Figure 2

Adjusted means and standard errors for temporal summation (TS) across sex. Women had overall higher heat pain ratings than men. The Sex × Trial interaction for 46 °C (knee) and 48 °C (arm, knee) was significant indicating that women had greater TS across the 5 repeated trials.