Pain, Sensitization, and physical performances in patients with chronic painful knee osteoarthritis or chronic pain following total knee arthroplasty: an explorative study.

Background The aim of this study was to assess clinical pain, pain sensitization, and physical performances to profile patients with chronic painful knee osteoarthritis (OA) or pain after total knee arthroplasty (TKA). Examining the interactions between pain mechanisms and physical performances would enable us to investigate the underlying explanatory relationships between these parameters. Methods In this explorative study, 70 patients with chronic painful knee OA (N=46) or chronic pain after TKA (N=24) were assessed for clinical pain, quantitative sensory profiling (mechanical pinprick pain sensitivity, temporal summation (TS), and conditioned pain modulation), physical performances (chair stand, walk, and stair climb tests), and self-reported outcomes. Between-group comparisons were made using ANCOVA tests and associations between outcomes were analyzed using multivariate linear regression models. Results Overall, no differences between groups regarding clinical pain and quantitative sensory profiling outcomes were observed. Physical performances were lower in the TKA group compared with the OA group with moderate-to-large effect sizes, and a tendency towards better scores in self-reported outcomes for the OA group was observed with small-to-moderate effect sizes. Self-reported function seems to be associated with physical performances in the TKA group. Sensitization (TS) appears to be associated with poorer physical performances in the OA group. Conclusions Similar profiles for pain intensity, signs of sensitization, and conditioned pain modulation were observed. Patients with TKA seem to have impaired physical performance compared with the OA group, underlining the importance of targeting physical performances. Only the OA patients showed an association between sensitization (TS) and physical performance.