Imaging description

The radiographic appearance of primary synovial chondromatosis is that of multiple round or oval calcified loose bodies, usually of similar size, and without underlying diseases that can be associated with loose body formation (Figure 86.1). In about one third of patients the loose bodies are not mineralized and radiographs may be normal or reveal only soft tissue swelling of the affected joint (Figure 86.2). In tight joints such as the hip, elbow, and ankle deep bony erosions are common (Figure 86.2). The extra-articular form of synovial chondromatosis is particularly rare. The hands, feet, and wrists are most commonly affected (Figure 86.3). In the hip joint both intra- and extra-articular involvement has been described; the extra-articular synovial chondromatosis in the hip often involves the iliopsoas bursa (Figure 86.4).

Secondary synovial osteochondromatosis is much more common than the primary type and it is seen in older patients. It typically occurs in conjunction with underlying osteoarthritis. The calcified loose bodies tend to be larger than those seen with the primary type, less in number, and more varied in size (Figure 86.5).

Importance

Primary or idiopathic synovial chondromatosis is a rare monoarticular disease characterized by the formation of multiple cartilaginous or osteocartilaginous loose bodies. The disease is commonly intra-articular but occasionally it can be extra-articular involving a tendon sheath or bursa. Secondary synovial chondromatosis is the more common type and it is seen as a result of other joint diseases such as osteoarthritis, osteochondritis dissecans, osteochondral fractures, and neuroarthropathy. In the literature different names have been used to describe this condition but currently the most frequently used terms are synovial chondromatosis or synovial osteochondromatosis when the loose bodies are ossified. Loose bodies can only become ossified if they have a blood supply and therefore are attached to the synovium.