Synovial cyst presenting as forearm mass

A 43-year-old man with rheumatoid arthritis that involved primarily the hands and feet was seen at Veterans Administration Wadsworth Medical Center, Los Angeles, for a painless mass on the left forearm. An antecubital synovial cyst was diagnosed on the basis of results of ultrasonography and arthrography. Arthrocentesis of the elbow joint yielded 5 ml of serous fluid. Intraarticular injection of a corticosteroid resulted in complete resolution of the mass within three days, thus surgery was avoided.