Synovial chondromatosis is a locally aggressive bone tumor of the cartilaginous type. It consists of several hyaline cartilaginous nodules and has the potential of becoming cancerous. Signs and symptoms
People usually complain of pain in one joint, which persists for months, or even years, does not ease with exercise, steroid injection or heat treatment, shows nothing on X-ray, but shows a definite restriction of movement. There are 3 defined stages to this disease:

early: no loose bodies but active synovial disease;
transitional: active synovial disease, and loose bodies;
late: loose bodies but no synovial disease;In the early stages of the disease it is often confused with tendinitis and/or arthritis. Once it reaches transitional the loose bodies become apparent with X-ray in greater than 70% of cases, with MRI often showing where xray fails. In experienced hands, ultrasound is also useful for the diagnosis.Rare and little known, with currently no known cure, the disease gradually forms blisters in the thin flexible membrane of the synovium, which calcify and enlarge. These nodules eventually break free and float around the joint space becoming larger – these add to the discomfort and stiffness of the joint. The affected tissue will show up as a semi-solid mass in an MRI scan, final diagnosis is usually confirmed by taking a biopsy. The disease generally affects only one of the larger weight bearing joints (hip, ankle, knee) – although the elbow, and wrist can also be affected.
The mutation has high penetrance and variable expression, which means that nearly all people with the gene show signs of the condition, but these signs can range from very mild to very obvious. Diagnosis
Epidemiology
The actual incidence of this disease is not known, but only 243 cases have been reported in the scientific literature, suggesting an incidence of on the order of one affected person in ten million people. References


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