A study evaluated predictors of poorer one-year pain and functional outcomes in patients with rheumatoid arthritis (RA) who underwent total hip arthroplasty (THA) or total knee arthroplasty (TKA). The single-center study included patients with RA aged 18 years or older undergoing THA or TKA. Preoperative data collection included Hip Osteoarthritis Outcome Score/Knee Osteoarthritis Score (HOOS/KOOS) disability and injury outcome scores and physician assessments of disease characteristics and activity (Disease Activity Score [DAS-28] and Crohn’s Disease Activity Index [CDAI]); patient-reported outcomes (PROs) were collected preoperatively and one-year postoperatively. Postoperative flares were identified weekly for six weeks; flares were defined as the concordance between patient report plus physician assessment. One-year data included 122 patients (85% were female): 56 THA patients and 66 TKA patients. More than half of the patients who reported flare status (n=68; 58.1%) experienced a flare within six weeks of surgery; of these patients, 37 (54.41%) had flare at baseline. Baseline disease activity was higher among patients with flare than those without, including DAS-28 erythrocyte sedimentation rate (3.88 vs. 3.07); HOOS/KOOS scores for pain and function were also significantly worse among patients with flare. There were no significant between-group differences in absolute changes in HOOS/KOOS pain and function from baseline to one year regardless of flare status. A significant negative correlation was observed between baseline DAS28 and one-year HOOS/KOOS function, suggesting that patients with lower disease activity had better pain and function. Functional outcomes did not largely differ between patients who did and did not report postoperative flares. In univariate analyses, white race, body mass index (BMI), flare, DAS28, and baseline HOOS/KOOS pain and function were predictive of one-year HOOS/KOOS pain; in multivariate analyses, when adjusting for clinical characteristics, DAS28 and BMI remained predictive of one-year HOOS/KOOS pain and function.