Is synovial osteo-chondromatosis a proliferative disease?

In a case of synovial osteo-chondromatosis of the knee joint, foci of hyaline and calcified cartilage in the synovial membrane exhibited neither MIB-1-positive cells nor mitotic figures. Loose bodies of the synovial fluid showed a different proliferation behavior. In addition to cartilaginous nodules without MIB-1-positive cells, some of the bodies contained nearly 17% cells with MIB-1 activity. Besides the huge number of cells expressing the proliferation-associated antigen, no mitoses, except for a rare, possibly pycnotic mitosis, could be detected. It is assumed that owing to delayed fixation of the chondrocytes surrounded by a broad hyaline cartilaginous matrix, mitoses of these cells can be completed even in the absence of physiological nutrition. The observation described may explain the occurrence of multiple loose bodies in osteo-chondromatosis. According to Milgram's theory, pedunculated nodules of the synovial membrane can become detached, and thereafter appear in the synovial fluid. In this nourishing environment, they can grow to a certain degree; larger ones perhaps become fragmented because of the force of movement, resulting in smaller particles that grow again. This indicates a vicious circle that leads to a myriad of loose bodies.