The effect of rheumatoid arthritis on patient-reported outcomes following knee and hip replacement: evidence from routinely collected data.

OBJECTIVES: To compare outcomes of total knee replacement (TKR) and total hip replacement (THR) for individuals with RA and OA. METHODS: We performed a cohort study using routinely collected data. Oxford Knee Score, Oxford Hip Score, and EuroQol 5-dimension 3-level (EQ-5D-3L) questionnaires were collected before and 6 months after surgery. Multivariable regressions were used to estimate the association between diagnosis and post-operative scores after controlling for pre-operative scores and patient characteristics. RESULTS: Study cohorts included 2070 OA and 142 RA patients for TKR and 2030 OA and 98 RA patients for THR. Following TKR, the median Oxford Knee Score was 37 [interquartile range (IQR) 29-43] for OA and 36 (27-42) for RA while the median EQ-5D-3L was 0.76 (0.69-1.00) and 0.69 (0.52-0.85), respectively. After THR, the Oxford Hip Score was 42 (IQR 36-46) for OA and 39 (30-44) for RA while the EQ-5D-3L was 0.85 (0.69-1.00) and 0.69 (0.52-1.00), respectively. The estimated effect of RA, relative to OA, on post-operative scores was -0.05 (95% CI -1.57, 1.48) for the Oxford Knee Score, -0.09 (-0.13, -0.06) for the EQ-5D-3L following TKR, -1.35 (-2.93, -0.22) for the Oxford Hip Score, and -0.08 (-0.12, -0.03) for the EQ-5D-3L following THR. CONCLUSION: TKR and THR led to substantial improvements in joint-specific scores and overall quality of life. While diagnosis had no clinically meaningful effect on joint-specific outcomes, improvements in general quality of life were somewhat less for those with RA, which is likely due to the systemic and multijoint nature of rheumatoid disease.