Volkmann pointed out that the abrasion of the bony surfaces is almost certainly aided by some alteration in the structure of the bone itself, which in its earlier stages is probably of the nature of a rare fying osteitis ; he observed that mere mechanical friction does not sufficiently explain the fact that grooving may take place on portions of the bony surfaces which are not yet denuded of their cartilaginous covering ; and he held that this rarefying change is followed later by a hardening process.
True bony ankylosis is an almost unknown result of arthritis de formans. Not entirely unknown, for it has been met with in the vertebral column, where this change has been described by Bowlby ; but in the joints of the limbs with their far greater mobility it never occurs. Neither is there any tendency to the production of fibrous adhesions, a process which is so conspicuous in some forms of artic ular disease, and even in the arthritis of bleeders, which presents in other respects changes closely resembling those of arthritis deformans.
The changes in the shafts of the long bones are far less conspicu ous than those of the articular portions, but, as Adams long ago pointed out, these portions also may exhibit an increase of size and of density.
Like the cartilages and bones, the synovial membranes are the seats of conspicuous morbid changes in arthritis deformans. In some cases in which operations have been performed upon joints thus diseased during the life of the patient, brilliant injection of the syn ovial membrane has been observed; but the most typical changes are the conspicuous thickening of the membrane, and the hypertrophy of the synovial fringes. Such hypertrophied fringes are conspicuous in all museum specimens of this disease. In the hypertrophied tufts fatty changes frequently take place, or they may become converted into cartilaginous masses which remain attached to the Surface of the membrane by slender pedicles. These pedicles are very apt to be ruptured, with the result that the pellets of cartilage become converted into loose bodies lying free in the articular cavity.
Similar cartilaginous masses may also be present in the in the neighborhood of the diseased joint, and are easily and fre quently to be detected by palpation in the bursa over the olecranon. It is not easy to understand how the opinion originated that one of the characteristics of arthritis deformans is the absence of any ten dency to the accumulation of fluid in the cavities of the affected joints ; yet it has frequently been asserted that this is the case, and one of the names assigned to the disease, viz., arihrite seche, was intended to emphasize this view. So far as my own experience goes, and I could support my opinion by quotations from many eminent authorities who have devoted attention to the subject, this statement is quite opposed to the facts, and effusion, often of considerable amount, is frequently present both in the cavities of the joints and in the in their immediate neighborhood, many of which are doubtless in direct communication with the articular cavities. We possess an analysis of the articular fluid from a case of arthritis deformans by no less an authority than Hoppe-Sey ler," which gives the following result : In the ethereal extract cholesterin, lecithin, and traces of fat were detected.
Next to the joint lesions the atrophy of muscles constitutes the most conspicuous change present in arthritis deformans. Post mor tem the affected muscles are obviously wasted and have a brownish tint which is compared by Debove to that of dead leaves. Debove has further shown that the atrophy is of the type met with as the result of nervous lesions, the degeneration of the various component fibres being conspicuously unequal in its degree. Changes of the nature of neuritis have been detected by Pitres and Vaillard" in several cases of this disease which they have examined, and the amount of change which the nerves had undergone appeared to stand in a direct relation to the degree of atrophy of the muscles supplied by them.