Lower extremity osteoarthritis in elderly patients with rheumatoid arthritis: prevalence, radiographic-clinical discordance, and functional impact - a cross-sectional study.

INTRODUCTION/OBJECTIVES: Osteoarthritis (OA) is common in rheumatoid arthritis (RA), but its radiographic distribution and functional impact in elderly patients remain poorly characterized. We aimed to determine the prevalence of radiographic and symptomatic lower extremity OA, characterize radiographic-clinical discordance, identify factors associated with knee OA, and assess its functional impact in elderly patients with RA. METHOD: In this single-center cross-sectional study, 230 patients with RA aged ≥ 60 years underwent standing full-length lower extremity radiography, joint-based clinical assessment by an orthopedist, and Lower Extremity Functional Scale (LEFS) evaluation. Radiographic OA was defined as Kellgren-Lawrence grade ≥ 2, and symptomatic OA as radiographic OA with corresponding clinical findings. Multivariable logistic and linear regression analyses were performed. RESULTS: Radiographic OA was present in 62.2% of patients and symptomatic OA in 22.2%, with the knee most frequently affected. Of 261 joints with radiographic OA, 72.4% lacked corresponding clinical findings. Older age, female sex, and higher body mass index were independently associated with both radiographic and symptomatic knee OA, while higher time-averaged Simplified Disease Activity Index and greater hip-knee-ankle angle were associated only with symptomatic knee OA. Radiographic OA was not associated with LEFS or Health Assessment Questionnaire Disability Index, whereas symptomatic OA at the hip, knee, and ankle was independently associated with worse function and disability. CONCLUSIONS: Lower extremity OA is highly prevalent in elderly patients with RA, with marked radiographic-clinical discordance. Symptomatic, rather than radiographic, OA was associated with functional impairment; cumulative inflammatory burden and limb malalignment may contribute to its expression. Key Points • Lower extremity OA affects over 60% of elderly RA patients, with marked radiographic-clinical discordance. • Symptomatic, not radiographic, OA is associated with functional impairment and disability in elderly RA patients. • Cumulative inflammatory burden and lower limb malalignment may contribute to symptomatic knee OA in RA.