[Intra-articular rheumatoid nodules of the knee joint]

Intra-articular rheumatoid nodules found in 6 knee joints of 4 patients with rheumatoid arthritis were reported with histological findings. All patients were women, ranging in age from 32 to 61 years, with 6 to 41-year history of rheumatoid arthritis. The masses were exclusively in the anterolateral aspect of the joint. Snapping occurred when the joint was flexed by 20 degrees in four joints and by 60 degrees in two. The masses had the sizes of a thumb tip to index-finger tip, and were elastic and soft. Histologic examination of the masses revealed the typical formation of rheumatoid nodule in two joints. Myxomatous degeneration and granulation tissue consistent with rheumatoid arthritis were found in two joints. Perivascular fibrosis and myxomatous degeneration were mainly demonstrated in two joints which had developed masses two months before excision.