There are many varieties of foreign bodies in joints.

The foreign osteocartilaginous bodies are, more often, of pathological origin, formed either from the synovial membrane or from the ends of the bones. Foreign bodies purely traumatic may exist, but undoubtedly are rare.

The traumas to the articulations play an important part in the production of the pathological processes which end in the formation of foreign bodies. The larger number of the articular foreign bodies arise from the processes in the dry arthritis deformans, of which these lesions are characteristic. Another important cause is the condition of that so called osteochondritis dissecans, of which the nature is not understood,—perhaps less distinctly than that of the dry arthritis. We do not admit the reality of the arthritic neoplasia, so called osteochondromatosis, as the origin of foreign bodies.

The pathological findings can best serve to recognize the different varieties of these articular foreign bodies.

The postoperative prognosis of these foreign bodies in joints is good, excepting certain cases in which there are pathological joint lesions which are definitely marked. The traumatic foreign bodies, and many of the pathological as well, may be removed with success and the joints remain normal.

The surgery of the articular foreign bodies is extremely useful.