Impact of disease duration on forefoot involvement in rheumatoid arthritis remission: clinical, ultrasound, and radiographic insights

BACKGROUND: Rheumatoid arthritis (RA) frequently affects the forefoot, causing pain and deformity even in remission. Subclinical inflammation may persist and vary with disease duration. This study aimed to compare clinical, ultrasound, and radiographic features of the forefoot in RA remission with metatarsalgia according to disease duration (< 10 vs. ≥ 10 years). METHODS: Cross-sectional study including 84 RA patients in remission (DAS28 < 2.6) with metatarsalgia: 33 with < 10 and 51 with ≥ 10 years of disease duration. Clinical, biomechanical, ultrasound (B-mode and Power Doppler (PD), and radiographic variables were assessed by blinded evaluators. RESULTS: The ≥ 10-year group showed greater structural burden. Total synovitis was similar between groups, more frequent at central metatarsophalangeal joints (MTPs) (particularly MTP2 in < 10 years), and PD was rare (6%). The overall pattern was consistent with early MTP1/5 involvement and progressive structural accumulation at MTP2-4, with higher odds of erosions (OR 3.5-5.0), joint space narrowing (JSN; OR 2.8-4.4), and subluxations (MTP2 OR 5.31; MTP3 OR 2.50) in the ≥ 10-year group. CONCLUSIONS: In RA remission with metatarsalgia, our findings are consistent with early structural involvement at MTP1/MTP5 and more frequent B-mode synovitis at central joints, with progressive structural burden at MTP2-4 as disease duration increases. PD positivity was uncommon (6%), whereas ultrasound remained essential to detect synovitis. Our findings support systematic assessment of all MTP joints (MTP1-5), with particular attention to MTP1/MTP5 in earlier disease and careful structural evaluation of central rays in longer disease duration. As a cross-sectional study, temporal or causal sequences cannot be inferred.