Synovial chondromatosis, also known as synovial osteochondromatosis, is a condition that occurs within synovial-lined joint capsules or bursae and is characterized by metaplasia of cells forming cartilaginous or osteochondral loose bodies. Proliferative and hypertrophic synovial villi undergo metaplastic changes into cartilaginous nodules, forming pedunculated structures within the joint. These nodules remain attached to the synovium via pedicles, which are supplied with nutrients by their vascular connections. The loose bodies continue to grow and may detach into the joint cavity, becoming "joint mice." The ossification centers of the loose bodies may undergo necrosis due to loss of blood supply, while their cartilaginous surfaces can continue to grow, nourished by synovial fluid.
Clinical Features
This condition is most commonly seen in individuals over the age of 40 and can affect any major joint, with the knee being the most frequently involved. The main symptom is sudden locking of the knee joint during movement. Radiographically, multiple calcified loose bodies of varying shapes and sizes can be observed within the joint or adjacent bursae, appearing as round or irregular calcifications. Arthroscopy can provide assistance for both diagnosis and treatment.
Treatment
Extensive synovectomy and removal of intra-articular loose bodies are the primary treatment approaches.