Background Cohort studies are essential to provide better understanding of the prognosis of acute monoarthritis, but few studies have focused on this issue.
Objectives To describe the joint distribution in a cohort of patients with new-onset monoarthritis, and to study the outcome after two years, according to the initial joint involved.
Methods 1084 patients (age 18-75 years) with arthritis of less than 16 weeks duration were included in the NOR-VEAC study from 2004 to 2010. Patients with crystal arthritis and osteoarthritis were not included. 354 patients (33%) had monoarthritis (clinical synovitis in one joint) at baseline. Follow-up data were available for 331 patients (94%), and 185 (52%) had 2-year follow-up data.
Results Duration of joint swelling [median (25-75 percentiles)] among the 331 patients with monoarthritis was 22 (7-48) days, mean (SD) age 45 (14) years, 51.2% were females, 5.9% anti-CCP positive, 10.1% anti-CCP and/or RF positive). The most frequently affected joints were knees (50.5%), ankles (17.5%) and wrists (13.9%).
12 patients (3.6%) fulfilled the 2010 ACR/EULAR classification criteria for rheumatoid arthritis (RA) at baseline; these had mostly wrist or small joint involvement. Two patients with clinical synovitis of the knee fulfilled the criteria as a result of one more tender joint. During follow-up 10 additional patients fulfilled the criteria, 8 of whom presented with large joint arthritis (table). No patients with ankle monoarthritis ever fulfilled the criteria, nor progressed to a clinical diagnosis of RA within 2 years of follow-up.
57 patients (17.2%) were diagnosed with reactive arthritis at baseline, 10 patients (3%) with psoriatic arthritis (PsA), and during follow-up only 4 more patients were classified as PsA. The patients diagnosed with PsA had monoarthritis of the knee (n=8), hand (n=2), wrist (n=2), elbow (n=1) and foot (n=1) at presentation. In addition two patients with arthritis of the knee and ankle were diagnosed with axial spondyloarthritis. In 236 patients (71%) the arthritis had resolved at last follow-up without DMARD treatment. 51 patients (15.4%) had DMARDs prescribed, 97 (29.3%) received intra-articular corticosteroids and 73 (22%) systemic corticosteroids.
Conclusions Few patients with acute or recent onset monoarthritis seem to develop chronic inflammatory joint disease over two years. Patients with ankle monoarthritis had an especially low likelihood of developing RA or other chronic rheumatic diseases.
Disclosure of Interest None Declared
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