Background and Objectives: Sarcopenia is a notable comorbidity of rheumatoid arthritis (RA), affecting about one third of patients. However, the characteristic of muscle function and its association with RA disease remains unknown. Materials and Methods: This cross-sectional study collected clinical data from a real-world Chinese RA cohort. Sarcopenia was defined as both myopenia and low muscle function (LMF). Myopenia was defined as appendicular skeletal muscle mass index (ASMI) < 7.0 kg/m² in men and <5.7 kg/m² in women. LMF was defined as low muscle strength (LMS, hand grip < 28 kg in men and <18 kg in women) or low physical performance (LPP, 6 m gait speed < 1.0 m/s). Results: Among 1125 RA patients recruited in this study, 928 RA patients were eligible for analysis. The prevalence of sarcopenia, myopenia, LMF, LMS, and LPP in all RA patients was 36.5%, 46.1%, 69.0%, 57.8%, and 37.1%, respectively. According to their trends in age and disease activity, there were 111 (11.9%) patients in the young (age < 50 years) and remission (CDAI ≤ 2.8) subgroup, 199 (21.4%) patients in the young and active (CDAI > 2.8) subgroup, 198 (21.3%) patients in the old (age ≥ 50 years) and remission subgroup, and 420 (45.2%) patients in the old and active subgroup. Compared with the two remission subgroups, respectively, the young and active subgroup had significantly lower grip strength, higher prevalence of sarcopenia, LMF, and LMS, and worse activity function. After adjustment for potential confounders, multivariate multinominal logistic regression analysis showed that the young and active subgroup was positively associated with sarcopenia (OR = 3.193, 95%CI: 1.477–6.899), LMF (OR = 2.390, 95%CI: 1.207–4.731), and LMS (OR = 3.520, 95%CI: 1.743–7.110). Conclusions: Worse muscle strength, rather than reduced physical performance, is more common in patients with active RA at a young age. It underscores the critical need for early identification and intervention of muscle dysfunction to improve their quality of life.

Background and Objectives: Hand joint deformity remains a main cause impairing quality of life in rheumatoid arthritis (RA). This study aimed to investigate the association between biologic and targeted-synthetic disease-modifying antirheumatic drugs (b/tsDMARDs) treatment and the prevalence of hand joint deformity in RA patients. Materials and Methods: This cross-sectional analysis included RA patients recruited between 2019 and 2024. Hand joint deformity was defined as the presence of specific deformity in any of 28 hand joints, including the metacarpophalangeal (MCP) joints I-V, proximal interphalangeal (PIP) joints I-V, and distal interphalangeal (DIP) joints II-V. The key exposure was the use of b/tsDMARDs. Multivariable logistic regression was used to assess the association between b/tsDMARDs treatment and hand joint deformity. Results: A total of 1083 RA patients with a mean age of 52.6 ± 12.4 years and a median disease duration of 5 (2,11) years were included. Hand joint deformity was present in 25.4% (275/1083) of patients. The top three deformed joint locations were PIP V (12.9%, 140/1083), PIP III (11.6%, 126/1083), and PIP IV (10.9%, 118/1083). The top three deformity types were ulnar deviation of MCP II-V (8.0%, 87/1083), boutonniere deformity of II-V fingers (6.8%, 74/1083), and swan neck deformity of II-V fingers (6.7%, 73/1083). In total, 17.4% (188/1083) of patients had received b/tsDMARDs. After 1:1 propensity score matching for age, sex, and disease duration, the prevalence of deformity was significantly lower in patients treated with conventional medicine (csDMARDs and/or GCs) add-on b/tsDMARDs compared to those treated with conventional medicine (27.1% vs. 61.7%, p < 0.001). Multivariable logistic regression analysis showed that b/tsDMARDs use was independently associated with a lower prevalence of hand joint deformity after adjusting for confounding factors (OR = 0.211, 95%CI: 0.129–0.345, p < 0.001). Conclusions: The use of b/tsDMARDs was independently associated with a lower prevalence of hand joint deformity in RA.