Giant intraosseous cyst-like lesions in rheumatoid arthritis report of a case.

The term "intraosseous synovial cyst" is used to designate both the epiphyseal cyst-like lesions seen in patients with rheumatoid arthritis (RA) and mucoid cysts, which occur in a different setting. We report the case of a patient in whom a 4-cm cyst-like lesion developed in the left tibia 18 years after onset of RA and 6 years after osmic acid synovectomy of the left knee. Positive contrast arthrography and magnetic resonance imaging visualized a communication between the lesion and the joint space.