Prevalence and trajectory of erosions, synovitis, and bone marrow edema in feet of patients with early rheumatoid arthritis

Despite erosions being as prevalent in feet as in hands in patients with rheumatoid arthritis (RA), their development in relation to synovitis and bone marrow edema (BME) have mainly been studied in hands. This study examines the prevalence and longitudinal trajectory of erosions, BME, and synovitis in metatarsophalangeal joints (MTPJs) in patients with early RA over 2 years of treatment. We also describe correlations between erosions, synovitis, and BME at the joint level. Magnetic resonance imaging (MRI) of the most symptomatic forefoot was acquired at baseline, year 1, and ≥ 2 years. Metatarsophalangeal joints 2-5 were scored by a radiologist for erosions, synovitis, and BME according to OMERACT guidelines. Patients were treated per standard of care. Thirty-two patients with early RA were included. Significant reductions in overall synovitis scores, MTPJ2, and MTPJ3 synovitis scores were seen between year 1 and ≥ 2 years. Overall BME scores improved in year 1 and were sustained at ≥ 2 years. BME improved in MTPJ2, MTPJ3, and MTPJ4. Overall erosions did not significantly change. Positive correlations were seen between changes in synovitis and BME in MTPJ2 and MTPJ5. In patients with early RA, standard of care was associated with overall reductions in synovitis by year 2, BME by year 1, and no progression in overall erosion scores on MRI. MTPJ2 and MTPJ3 appeared to be the most active joints. Improvements in synovitis were noted in MTPJ2 and MTPJ3 and reductions in BME in MTPJ2, MTPJ3, and MTPJ4, while other MTPJs did not progress. Key Points • This is one of the few MRI studies that examined longitudinal changes in imaging outcomes in early RA at the joint level in feet. • Erosions, synovitis, and bone marrow edema (BME) visualized on magnetic resonance imaging were most prevalent in metatarsophalangeal joints (MTPJ) 2 and 3 in patients with early rheumatoid arthritis (RA). • Standard of care was associated with improvements in synovitis in MTPJ2 and MTPJ3 and improvements in BME in MTPJ2, MTPJ3, and MTPJ4 over 2 years of treatment.