Abstract In the present study, 49 knee joints of 26 patients with rheumatoid arthritis and 17 knee joints of 17 healthy subjects were ultrasonographically examined. Lateral, superior, and medial aspects of the patella were scanned using an ultrasonograph with a 7.5-MHz annular array transducer to evaluate the thickness of synovial effusion and the synovial proliferation pattern. The overall mean thickness of synovial effusion (mean of all three sites) in the knee joints was 4.9 - 3.4 mm for rheumatoid arthritis patients and 1.4 - 0.5 mm for healthy subjects. In rheumatoid arthritis patients, the mean thickness of synovial effusion at the superior aspect of the patella (6.5 - 4.1 mm) was significantly greater than that at the lateral aspect (4.5 - 4.8 mm) (P < 0.05) and the medial aspect (4.0 - 3.1 mm) (P < 0.01). Patients with the villonodular pattern of synovial proliferation had a shorter duration of disease than those with uniform thickening or an overlapping pattern.
