The patient is a 43 year old man without significant past medical history who has noted increasing discomfort and progressive “loss of flexibility” in his right shoulder over the last several months. He does not recall any recent trauma, and denies any fevers, night sweats, skin rashes, fatigue, or other systemic symptoms. His general physical examination is unremarkable, but examination of the right shoulder reveals marked swelling, mild erythema, and highly restricted range of motion in several planes. Radiographs of the shoulder are obtained.
Plain X-rays of the shoulder reveal multiple large intra-articular calcified cartilaginous bodies of roughly equal size (red arrows) without significant joint space narrowing, erosions, or osteopenia. They are noted throughout the glenohumeral joint.
Diagnosis and Discussion
Correct Diagnosis: Synovial Osteochondromatosis
Synovial osteochondromatosis (SO) is a rare condition characterized by the gradual ossification of intra-articular cartilaginous structures. It is more commonly seen in men, and often appears in the 4th and 5th decades of life. The disease is usually monoarticular, with the knee being most commonly affected site. Several small series and case reports, however, have described involvement in many locations, including the shoulder, hip, ankle, and temporomandibular joints.
While primary idiopathic SO is a rare condition, secondary SO is more commonly seen in patients with osteoarthritis. In these patients, SO manifests radiographically as multiple osteocartilaginous loose bodies in the setting of characteristic OA changes in the adjacent joint. The pathology of these lesions is that of chondroid metaplasia, and though extremely rare, malignant transformation to synovial chondrosarcoma can occur. Because of the presence of foreign bodies in the joint, treatment of the pain, swelling, and motion restriction is usually treated surgically with synovectomy and loose body removal. When possible, these procedures can be done arthroscopically.
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