[A study of MRI diagnosis for rheumatoid arthritis in the knee joint--imaging and pathologic correlation].

We performed MR (magnetic resonance) imaging of 25 knee joints in 20 patients with rheumatoid arthritis (RA) before synovectomy and the findings were compared with the pathological specimens. When based on the findings on T2-weighted images of the examined joints, the degree of joint involvement by RA could be divided into four stages: stage 1 in which only joint effusion was present; stage 2 in which synovial thickening, lower in signal intensity than joint effusion, was present; stage 3 in which cartilage destruction was present; stage 4 in which apparent bone destruction was present. There were eleven joints which appeared unremarkable on conventional X-ray films but three of them were at stage 2 and six at stage 3. In conclusion, MR imaging is of help in diagnosis of early involvement of the knee joints by RA.