Disease-specific pain and function predict future pain impact in hip and knee osteoarthritis.

The objective of this study is to determine if osteoarthritis (OA) pain and function, persistent low back pain (LBP) and psychosocial factors predict future pain impact (PI) in people with hip and knee OA. In a population-based cohort with hip/knee OA, a standardized telephone questionnaire was used to assess baseline sociodemographics, baseline PI, patient-reported OA severity (Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) summary score), psychosocial factors (fatigue, pain catastrophizing (PC), anxiety, social network, and depression), and self-reported persistent LBP. Two years post-baseline, PI was assessed using the Pain Impact Questionnaire. The association of key independent variables with PI was evaluated through multivariable linear regression, adjusting for covariates (e.g., age, sex, baseline PI, etc.) In 462 participants, the mean age was 76 years (range 58 to 96), 78 % were female and 35 % reported LBP at baseline. Mean scores for PC (9.4), and anxiety (3.7) were low and social network (20.1) high. In multivariable regression analyses, only the WOMAC summary score (unstandardized ß 0.181 95% CI (0.12, 0.24) p < 0.001) was independently associated with greater PI at follow-up. In a population-based cohort with hip/knee OA, only the baseline WOMAC summary score was an independent predictor of future PI. This suggests that treatment needs to be focused on limiting pain severity and functional limitations in individuals with hip and knee OA. However, scores for the psychosocial factors are indicative of a healthy cohort and therefore results may not be generalizable to those with poorer psychosocial health.