The diagnostic dilemma of undifferentiated inflammatory synovitis of the knee joint/joints: a comprehensive approach

Can Magnetic Resonance Imaging Differentiate Undifferentiated Arthritis Based on Knee Imaging?

Objective.

To compare findings as observed on enhanced magnetic resonance imaging (MRI) of the knee joints, in oligoarticular-undifferentiated arthritis (UA) in those with established rheumatoid arthritis (RA) and spondyloarthropathy (SpA).

Methods.

A total of 55 patients with knee arthritis were consecutively recruited for the study, including 25 with undifferentiated oligoarthritis of the knee joint(s), 15 fulfilling the American College of Rheumatology criteria for RA and 15 with SpA. Laboratory investigations included erythrocyte sedimentation rate, C-reactive protein, complete blood count, aspartate aminotransferase, alanine aminotransferase, serum creatinine, and urine analysis. In all patients in the UA and in the RA group, rheumatoid factor and anti-CCP2 antibody (ELISA) were tested. All patients underwent enhanced MRI of the more symptomatic knee. All groups were compared in terms of demographics, laboratory investigations, and MRI findings.

Results.

Synovial thickness differed significantly in the RA group compared to UA and SpA groups (p < 0.001). The RA group showed a higher rate of bony and cartilaginous erosions and bone marrow edema compared to UA and SpA groups (p < 0.001). Enthesitis was found in all patients in the SpA group (100%) and differed from RA and UA groups (p < 0.001).

Conclusion.

Patients with RA showed more destructive changes in terms of synovial thickening, bone marrow edema, cartilaginous and bone erosions compared to UA and SpA groups. Enthesitis is a common feature on MRI in SpA, while absent in the RA and UA groups. This latter finding may have important clinical implications for classification purposes, and can help to determine the evolving pattern of patients with UA of the knee joint.

Enhanced MRI in early undifferentiated oligoarthritis of the knee joints: improvements already visible after 2 months of DMARDs treatment

To describe (1) the findings with MRI in a series of patients with early undifferentiated oligoarthritis of the knee joint(s) and (2) the early effect after 2 months of treatment with only methotrexate (MTX) and hydroxychloroquine (HCQ) as disease-modifying antirheumatic drugs (DMARDs), 15 consecutive patients with undifferentiated oligoarthritis of the knee joint(s) were recruited. The mean age was 31.7 years (SD = 8.1 years), and the mean disease duration was 15.3 months (SD = 12.2 months). In all patients, synovial fluid analysis, RF, anti-CCP2 antibodies, ANA, CRP, ESR, and routine laboratory investigations were performed. Enhanced MRI was done at initial evaluation and after 2 months treatment. Four of the 15 patients had positive RF and 6 had positive anti-CCP2. After treatment with DMARDs, a regression was seen regarding effusion and synovitis in all patients; in one of three patients, the bone edema had regressed. Synovial thickening as measured by enhanced MRI decreased significantly (p < 0.01) and correlated significantly with the improved ESR and CRP (p < 0.01). After 2 months treatment with MTX and HCQ, the MRI improved considerably especially regarding synovial thickening.