Knee joint bursal abnormalities in rheumatoid arthritis.

Twenty-five patients with rheumatoid arthritis presented with knee joint bursal abnormalities. Nineteen patients presented with symptoms simulating thrombophlebitis. Sixteen had a rupture of the posterior joint capsule without a communicating semimembranosus-gastrocnemius bursa (S-G), with extension ventrally between the soleus and gastrocnemius muscles or between the skin and muscle. Nine had an enlarged S-G bursa with or without rupture. Two patients had additional cephalad ruptures: one from the posterior compartment and the other one from the suprapatellar bursa.