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. 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.