Last updated: November 4, 2014
ICD-9 Code: 727.82.
Definition: Synovial osteochondromatosis is a benign monarticular process characterized by intraarticular calcific bodies that mainly affects large arthrodial joints.
Etiology: Although the majority of cases are idiopathic, synovial osteochondromatosis has also been suggested to be associated with other preexisting articular conditions, such as OA, RA, neuropathic arthropathy, osteonecrosis, and trauma.
Pathology: Metaplastic changes in the synovium result in the formation of cartilaginous bodies that protrude into the joint space. Bone formation in the cartilage and calcification subsequently develop. Detachment from the synovium leads to multiple intraarticular loose bodies. Although considered benign from a clinical standpoint, clonal proliferation has been demonstrated within lesions, suggesting a neoplastic process. However, malignant transformation to chondrosarcoma appears to be a very rare event.
Demographics: Men are affected about twice as often as women. Diagnosis is usually made between 20 and 40 years of age.
Cardinal Findings: The knee is affected in >50% of cases. Other joints commonly involved include the hip, elbow, and shoulder. Small joints are uncommonly involved. Patients typically complain of pain in the affected joint, sometimes associated with loss of motion or catching. Physical examination findings are nonspecific.
Diagnosis/Imaging: The diagnosis is almost always made by radiography, with characteristic multiple, rounded, intraarticular calcified nodules of similar size. The diagnosis can be confirmed by MRI, particularly in cases in which calcification is less prominent.
Differential Diagnosis: Synovial sarcoma, gout, CPPD crystal deposition disease, hydroxyapatite disease, scleroderma (with calcinosis).
Therapy: Surgical removal of symptomatic intraarticular bodies, via arthroscopy if possible, is the standard treatment.
Ozark L, Demos T, Lomasney L, et al. Synovial osteochondromatosis. Orthopedics 2000; 23:513–516.PMID:10825102