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Objective: Pain persistence following knee replacement (KR) occurs in ∼20–30% of patients. Although several studies have identified preoperative risk factors for persistent post-KR pain, few have focused on post-KR contributing factors. We sought to determine whether altered nociceptive signaling and other peripheral nociceptive drivers present post-operatively contribute to post-KR pain. Design: We included participants from the Multicenter Osteoarthritis Study who were evaluated ∼12 months after KR. We evaluated the relation of measures of pain sensitivity [pressure pain threshold (PPT), temporal summation (TS), and conditioned pain modulation (CPM)] and the number of painful body sites to post-KR WOMAC knee pain, and of the number of painful sites to altered nociceptive signaling using linear or logistic regression models, as appropriate. Results: 171 participants (mean age 69 years, 62% female) were included. TS was associated with worse WOMAC pain post-KR (β ​= ​0.77 95% CI:0.19–1.35) and reduced odds of achieving patient acceptable symptom state (aOR ​= ​0.54 95%CI:0.34–0.88). Inefficient CPM was also associated with worse WOMAC pain post-KR (β ​= ​1.43 95% CI:0.15–2.71). In contrast, PPT was not associated with these outcomes. The number of painful body sites present post-KR was associated with TS (β ​= ​0.05, 95% CI:0.01, 0.05). Conclusions: Post-KR presence of central sensitization and inefficient descending pain modulation was associated with post-KR pain. We also noted that presence of other painful body sites contributes to altered nociceptive signaling, and this may thus also contribute to the experience of knee pain post-KR. Our findings provide novel insights into central pain mechanisms and other peripheral pain sources contributing to post-KR persistent knee pain.

Summary: Objective: With adults working to older ages, occupation is an important, yet less modifiable domain of physical activity to consider in the risk of knee osteoarthritis (OA). This study aimed to investigate the association between predominant lifetime occupation and prevalent knee OA. Design: Participant-level data were used from five international community-based cohorts: Johnston County Osteoarthritis Project, the Hertfordshire Cohort Study, the Multicenter Osteoarthritis Study, the Tasmanian Cohort Study and Framingham Osteoarthritis Study. Self-reported predominant occupation was categorized into sedentary, light, light manual and heavy manual levels. Cross-sectional associations between predominant lifetime occupation and knee OA outcomes including prevalence of radiographic knee OA (RKOA), symptomatic RKOA and knee pain, were assessed using logistic regression, accounting for cohort clustering. Results: Data for 7391 participants were included. 24.7% reported sedentary lifetime occupation, 30.0% light, 35.9% light manual and 9.4% heavy manual. 43.3% presented with RKOA, 52.1% with knee pain and 29.0% with symptomatic RKOA. There was over a two-fold increase in the odds of having RKOA, knee pain and symptomatic RKOA in those whose with heavy manual compared to sedentary occupations ((odds ratio (OR): 2.14; 95% confidence interval (CI): 1.79, 2.58), (OR: 2.19; 95% CI: 1.78, 2.70), (OR: 2.41; 95% CI: 1.94, 2.99) respectively). Conclusion: This large international multi-cohort study demonstrated an association of heavy manual work with RKOA, symptomatic RKOA and knee pain. Measures that protect workers and are designed to reduce heavy manual related activities remain a priority to reduce the risk of knee OA.