Pigmented villonodular synovitis of the hip presenting as a buttock mass treated by total hip arthroplasty.

Pigmented villonodular synovitis (PVNS) of the hip is a relatively uncommon benign but locally aggressive disease that should be considered in younger patients presenting with monoarticular joint symptoms. Pigmented villonodular synovitis begins in and usually remains confined within a synovium-lined joint, but rarely, it may extend beyond the joint capsule and present as a soft tissue mass. The authors report a previously unrecognized presentation of PVNS of the hip in a 36-year-old man, who presented with a buttock mass arising from the right hip joint. The patient was treated by synovectomy and total hip arthroplasty.