Characteristics of functional impairment in patients with long-standing rheumatoid arthritis based on range of motion of joints: Baseline data from a multicenter prospective observational cohort study to evaluate the effectiveness of joint surgery in the treat-to-target era

<p><b>Objective:</b> To explore the characteristics of functional impairment in patients with established rheumatoid arthritis (RA) based on the range of motion (ROM) of joints in a prospective observational study of RA patients undergoing joint surgery.</p> <p><b>Methods:</b> We collected data on demographics, Health Assessment Questionnaire Disability Index (HAQ-DI), and the ROM of large joints including the shoulder, elbow, wrist, hip, knee, and ankle. Associations between the ROM of each joint and disability in the eight HAQ-DI categories were determined using receiver operating characteristic (ROC) and logistic regression analyses. ROM cut-off values of each joint for the absence of disability in each HAQ-DI category were determined using ROC curves.</p> <p><b>Results:</b> A total of 460 patients were enrolled and analyzed in this study. Based on ROC analysis, the ROM of each joint was significantly associated with disability in each category. After adjusting for disease activity, age, and sex, shoulder abduction had the highest independent impact on disability in activity [cut-off: 139 degrees (OR: 5.26)], elbow flexion-extension in dressing [121 degrees (OR: 2.22)], wrist flexion-extension in reach [86 degrees (OR: 2.71)], hip flexion-extension in walking [126 degrees (OR: 3.42)], and knee flexion-extension in walking [134 degrees (OR: 2.97)].</p> <p><b>Conclusions:</b> Limited ROM of multiple joints was significantly associated with functional impairment in patients with long-standing RA. Motion in daily activity involves multiple joints, and at least two joints were independently involved in disability.