Rheumatoid arthritis and tuberculous arthritis: differentiating MRI features

The purpose of our study was to determine the MRI findings of rheumatoid arthritis (RA) and tuberculous arthritis, with emphasis on differential diagnostic features.

MR images of 63 joints in 62 patients with clinically or pathologically proven RA (36 joints in 35 patients) or tuberculous arthritis (27 joints in 27 patients) were evaluated retrospectively with regard to pattern and degree of synovial thickening, size of bone erosions, rim enhancement at bone erosions, degree of bone marrow and periarticular soft-tissue edema, and presence and number of extraarticular cystic masses. MRI findings were compared between RA and tuberculous arthritis by statistical analysis using kappa statistics, the Mann-Whitney U test, linear-by-linear association, and the chi-square test.

Nonuniform and greater degree of synovial thickening was more frequent in RA (p < 0.01); the thicker the synovial membrane, the greater the likelihood of RA (p < 0.01). Bone erosions of tuberculous arthritis were larger (p < 0.01), and the likelihood of tuberculous arthritis increased proportionally to the increment of size of the bone erosions (p < 0.01). Rim enhancement at bone erosion was more frequent in tuberculous arthritis (p < 0.01). Extraarticular cystic masses were more frequently seen and more numerous in tuberculous arthritis (p < 0.01).

Uniform synovial thickening, large size of bone erosion, rim enhancement at site of bone erosion, and extraarticular cystic masses were more frequent and more numerous in tuberculous arthritis. MRI may be helpful in the differentiation between RA and tuberculous arthritis.