BACKGROUND: We aimed to evaluate the prevalence of foot and/or ankle arthritis (FAA) and its impact on clinical indices in patients with rheumatoid arthritis (RA). METHODS: This cross-sectional study used data from the Korean College of Rheumatology Biologics & Targeted therapy registry to observe clinical outcomes of patients undergoing biologics therapy and conventional therapy. FAA was defined as ≥1 tender or swollen joint in the ankle and/or 1st-5th metatarsophalangeal (MTP) joints. Disease Activity Score 28 (DAS28), Routine Assessment of Patient Index Data 3 (RAPID3), Simplified Disease Activity Index (SDAI), and Clinical Disease Activity Index (CDAI) were assessed. RESULTS: Among 2046 patients, 598 had FAA. The ankle joint was the most commonly involved joint in FAA (tender joint, 71.4%; swollen joint, 59.5%), followed by the third and second MTP joints. Patients with FAA showed higher DAS28, RAPID3, SDAI, and CDAI scores. FAA presence was significantly associated with non-remission as per DAS28-ESR (odds ratio, 3.4; 95% confidence interval, 2.0-5.8), DAS28-CRP (3.6, 2.4-5.3), SDAI (6.3, 2.8-14.6), CDAI (7.6, 2.4-24.3), and RAPID3 (5.6, 2.7-11.5) indices on adjusting for age, sex, disease duration, presence of rheumatoid factor, presence of anti-cyclic citrullinated peptide antibody, lung disease, use of methotrexate, and previous use of biological disease-modifying anti-rheumatic drugs. Patients with FAA were less likely to achieve remission of SDAI (n = 6, 1.0%) and CDAI (n = 3, 0.5%) than that of DAS28-ESR (n = 21, 3.5%), DAS28-CRP (n = 38, 6.4%), and RAPID3 (n = 12, 2.0%). CONCLUSIONS: FAA represents a severe disease activity and is an independent risk factor for non-remission in patients with RA.