Synovial Chondromatosis of the Shoulder without Calcification on Plain Radiograph

Abstract

Synovial chondromatosis is a rare metaplastic condition that comprises a proliferation of cartilaginous bodies within the synovial membrane, bursa, or tendon sheath. It is characterized by the formation of multiple cartilaginous foci within the synovium that eventually break free to form loose bodies. It is often monoarticular and most commonly affects the knee joint and, to a lesser extent, the hip, elbow, wrist and ankle joints. There have been reports of synovial chondromatosis within the shoulder joint and, less commonly, extra-articular disease within the subacromial bursa. In reported cases, there is evidence of ossification on plain radiograph, as confirmed by magnetic resonance imaging (MRI). We present a histologically confirmed case of subacromial synovial chondromatosis, with evidence to confirm the diagnosis on MRI, but without evidence of calcification visible on plain radiographs.