Giant synovial cyst of the hip joint.

Synovial cysts are known to occur in patients with rheumatoid arthritis. Their presentation in the hip joint, however, continues to be a diagnostic challenge. A case is presented involving a patient with a large synovial cyst of the hip, emphasizing the need for the orthopaedic surgeon to include synovial cyst in the differential diagnosis of a painless groin mass, particularly in patients with rheumatoid arthritis.