[Classification and growth of loose bodies in joints (author's transl)]

A loose body in a joint can be attributed to various factors, such as osteochondritis dissecans, osteochondral fracture, synovial chondromatosis, or fracture of osteophytes in osteoarthritis. Some of the cases involving loose bodies in joints have evident etiological factors identified on the basis of radiographic and/or operative findings, while the others have etiological factors which have not yet been clarified. We have therefore investigated loose bodies taken from joints at arthrotomy and attempted to establish the process involved in their growth by histopathological, microradiographic and fluorescence-microscopic, and scanning electron microscopic means, and tried to clarify whether it is feasible to assess the etiological factors from these findings. The results revealed that the loose body in the joint is surrounded eventually by fibrous tissue, the lower layer of which forms osteo-cartilaginous tissue and that, in the center of the loose body, degenerated osteocartilaginous tissues from which etiological factors can be suspected are located, and the author mentioned that etiological diseases of the loose body could possibly be suggested from the studies on their microfine structures. It was furthermore clarified that the loose body is fed by synovial fluid and grows, and yet the rate of the growth is extremely slow.