Synovial cyst of the hip in a patient with rheumatoid arthritis.

A 67-year-old woman with rheumatoid arthritis (RA; Steinblocker stage IV, class 4) who had RA onset at 34 years of age had anterior thigh pain, femoral neuropathy and lower abdominal pain. Physical examination showed multidirectional limit of motion, and radiographic examination showed destruction of the hip joint. MRI and arthrography indicated a cystic lesion that communicated with the hip joint. The rheumatoid synovial cyst was removed during total hip arthroplasty. The symptoms were relieved, and the mass was reduced in size.