Background/Purpose: Arthritis in the lower extremities has a major impact in many patients in rheumatoid arthritis (RA), but has not been extensively studied. The objective of this study was to investigate the relation between inflammatory joint involvement and disability related to the lower extremities in early RA.

Methods: An inception cohort of patients with early RA (symptom duration ≤12 months), recruited in 1995-2005, was investigated and followed in a structured program. All patients were examined by the same rheumatologist. To estimate disability based on self-reported activity limitations, we used the Health Assessment Questionnaire Disability Index (HAQ-DI). In order to more specifically address disability of the lower extremities, we calculated a sub score, HAQ-DI lower extremities (HAQ-DI-LE), based on the 10 questions that cover activities that are mainly dependent on function of the lower extremities (Ekdahl et al. J Clin Epidemiol 1989; 42: 947-54). HAQ-DI LE scores in those with vs without current synovitis of individual joints were compared using the Mann Whitney test.

Results: A total of 233 patients with early RA (70 % women, mean age 60.5 years, median symptom duration 7 months) were investigated. The median HAQ-DI LE at inclusion was 0.6 (interquartile range 0.2-1.2). Knee synovitis, ankle synovitis and MTP joint synovitis was present at inclusion in 18 %, 26 % and 39 %, respectively. Proportions with synovitis in the lower extremities declined over time (Table). Knee synovitis was associated with significantly higher HAQ-DI-LE scores at inclusion (p<0.001) and after 6 months (p=0.01), but not at later follow-up visits (Table). Patients with ankle synovitis had higher HAQ-DI-LE at 6 months (p=0.02), 1 year (p=0.006) and 2 years (p<0.001). MTP joint synovitis was also associated higher HAQ-DI-LE, in particular at baseline (p=0.045). However, differences in HAQ-DI-LE for those with vs without synovitis were numerically smaller at 1 year and at 2 years for MTP joint synovitis compared to ankle synovitis (Table).

Conclusion: Knee synovitis was associated with disability related to the lower extremities, in particular in very early RA, whereas ankle synovitis had a greater impact after 1-2 years than at diagnosis. Large joint synovitis may be more important for lower extremity function compared to synovitis of the MTP joints. These findings underline the importance of assessment of the joints of the lower extremities in patients with RA.