Synovial osteochondromatosis of the ankle secondary to acute injury to bone.

Synovial osteochondromatosis is a benign lesion characterized by multiple cartilaginous and osteocartilaginous nodules of the synovium, as well as loose bodies within the joint. Present theories of origin include spontaneous metaplastic changes of the synovial cells or bursal tissues, which form foci of cartilage. The cartilage detaches, enters the joint cavity, and ultimately becomes calcified and ossified. Several authors have suggested trauma to the synovial tissues as being causative, but this has never been statistically confirmed. Others have even mentioned the spontaneous metablastic changes of chondrocytes as a possible etiology in some select cases. The origin of these chondrocytes has been assumed to be the synovial tissues. This paper questions the origin of chondrocytes--that they may sometimes originate from damaged interarticular bone. Also, they may form in a fashion similar to the extra-articular, solitary osteochondroma in which trauma plays a role in leading to the metaplasia of chondrocytes in the epiphysis. In the synovial osteochondromatosis, trauma to the interarticular bone may also result in a metaplasia of chondrocytes. The following case presents a history of ankle injury, leading to the formation of synovial osteochondromatosis in a relatively short time span. A pathologic review of osseous fragments removed from the joint revealed that an active reparative process had been initiated, suggestive of trauma to the bone as one possible cause of formation of synovial osteochondromatosis in an adolescent.