Functional ability in knee osteoarthritis: role of neuropathic pain and central sensitization

BackgroundPain in osteoarthritis (OA) has been attributed traditionally to local tissue injury causing 'nociceptive pain'. However, recent studies suggest that neuropathic and central sensitization mechanisms may contribute to the pain experience. However, the relationship between these pain mechanisms and physical function has not been thoroughly addressed. This study aimed to assess the association of central sensitization and neuropathic pain with physical function in knee OA.ResultsParticipants with a positive central sensitization inventory score (CSI) (>= 40) had a decreased total Knee injury and Osteoarthritis Outcome Score (KOOS) and its subscales (p < 0.001), a longer timed up and go test time (p = 0.002) and a higher PainDETECT questionnaire (PD-Q) and visual analogue scale (p < 0.001, p = 0.026 respectively). The severity of Kellgren-Lawrence grading (KL) (p < 0.001), depressive and anxiety symptoms (p < 0.001) increased with neuropathic pain severity. In addition, participants with a high PD-Q score (>= 19) had a longer timed up and go test time (p < 0.001) and a decreased total KOOS score (p < 0.001). Moreover, we found that CSI score, KOOS score, and KL grading were significantly predicted the PD-Q score (p = 0.046, p < 0.001, p = 0.007, respectively). Regarding the physical function predictors, multivariate linear regression analysis revealed that pressure pain threshold at right elbow and right knee (p = 0.005, p < 0.001) in addition to PD-Q (P < 0.001) were significantly associated with KOOS score, while CSI and Hospital Anxiety Depression Scale were not.ConclusionKnee OA patients with significant central sensitization and neuropathic pain reported increased pain, more functional impairment, more anxiety and depressive symptoms than OA patients without central sensitization and neuropathic pain. Additionally, neuropathic pain and presence of central sensitization were significant predictors for functional ability.