•  Tumor is composed of cartilaginous tissue.

•  Note the bosselations and the hard but pliable appearance typical of cartilage.

•Unknown.

•Appears to be a metaplastic disorder.

•Fibroblasts in the synovial stroma convert to a developmental program of chondrocytes instead of fibroblasts.

•They are nourished by synovial fluid and stimulated to proliferate, giving rise to a tumor like mass attached to the synovium.

•At the center of the chondroblastic mass, further metaplasia results in the formation of osteocytes, which form bone.

•Most cases occur after 40 years of age.

•Predominantly found in males.

•Could affect range of movement of a joint.

•Long term can cause degenerative joint disease.

•Can recur after resection.

•Knee is the joint most commonly affected.

•Also referred to as synovial chondromatosis and synovial chondrometaplasia.

•The most appropriate term seems to be the last, since this lesion seems to represent a metaplatic rather than neoplastic disease.

•Chondrocytes appear at the tips of synovial villi.

•Proliferation results in the formation of small masses.

•Grossly, there are cartilagenous masses attached to the synovial membrane.

•Subsequent detachment results in the formation of free chondromatous bodies lying free in the joint space.

•These are called joint mice.

•Composed often of a core of normal bone, surrounded by cartilage
.

•Both the cartilage and bone are histologically benign.

•E. Aegerter and J.A. Kirkpatrick, Jr. Orthodpedic diseases, 4th Edition. Philadelphia: W.B. Saunders, 1975. pp 682.

• Current literature from PubMed at National Library of Medicine