Findings: This is a single radiograph of the left hip demonstrating multiple calcifications located within the region of the synovium. These are rounded ossific densities with central lucencies. In addition, there is erosion of the femoral head. The ossific densities demonstrate a rather uniformity in shape and size.

Diagnosis: Synovial osteochondromatosis.

Discussion: Idiopathic synovial osteochondromatosis is an uncommon entity characterized by the formation of multiple cartilaginous nodules within the synovium. The exact pathogenesis of synovial osteochondromatosis is not entirely known. Synovial osteochondromatosis nearly always occurs within joints, but occasionally it occurs within bursa and tendon sheaths. One theory is that idiopathic synovial ostechondromatosis is a disease caused by hypometaplasia of the synovial connective tissue. Synovial osteochondromatosis occurs primarily in patients from the third through fifth decades, but it may affect any age group. It is somewhat more common in males than females and almost always affects large joints. The most common affected joints are the knee, hip, elbow, and shoulder. Extra-articular locations are uncommon. Patients generally present with chronic pain, stiffness, and swelling. The symptoms are slowly progressive with the eventual development of secondary degenerative osteoarthritis. In approximately 5 to 30% of cases there may be no identifiable calcifications within the joint. Well defined bony erosions may be identified. The most common finding is multiple rounded calcified or ossified loose bodies within the expected position of the synovium. These rounded densities often have central lucencies. The densities are often uniform in size as well as distribution throughout the joint. There have been a few reported cases of malignant transformation to synovial chondrosarcoma.

Reference:
Crotty JM. Synovial Osteochondromatosis. Radiologic Clinics
of North America 1996;34(2):327-341.

Return to Musculoskeletal Teaching File Page