Synovial chondromatosis of the shoulder: imaging findings

Synovial chondromatosis is a benign condition characterized by synovial proliferation and metaplasia, with development of cartilaginous or osteocartilaginous nodules within a joint, bursa or tendon sheath. In the shoulder, synovial osteochondromatosis may occur within the glenohumeral joint and its recesses (including the tendon sheath of the biceps long head), and in the subacromial-deltoid bursa. Such condition can be identified either by radiography, ultrasonography or magnetic resonance imaging, showing typical features according to each method. Radiography commonly shows ring-shaped calcified cartilages and periarticular soft tissues swelling with erosion of joint margins. Ultrasonography demonstrates hypoechogenic cartilaginous nodules with progressive increase in echogenicity as they become calcified, with development of posterior acoustic shadow in case of ossification. Besides identifying cartilaginous nodules, magnetic resonance imaging can also demonstrate the degree of synovial proliferation. The present study is aimed at describing the imaging findings of this entity in the shoulder.