The primary ulcer commences towards the centre of the cartilage, and always on its free surface. It is accompanied with much pain, but when exposed to view exhibits no sign of inflammation. There is no vascularity to be observed, no granulations, frequently no pus, nor any unhealthy appearance of the synovial membrane. Should the ulcer, however, have extended itself quite through the cartilage to the bone, the latter usually becomes carious, pus is secreted abundantly, and the synovial membrane sympathizes. The surface of the ulcer differs very much in different cases ; in some it appears smooth, and of the colour of healthy cartilage, as if a portion were chiselled out. In others, and more generally, it is a little yellowish, dull looking, and slightly irregular. The edges are often irregular, never elevated nor undermined. The ulceration sometimes spreads superficially over a large extent ; at other times it is small and deep, or it may destroy all the cartilage and expose the bone, which will also be found diseased. Most generally the remaining cartilage, if any, retains its healthy structure to the very edge of the ab sorbed portion.
Another appearance is often observed; a part of the cartilage is reduced to a fibrous state, the fibres being attached at one extremity to the bone, while at the other they are free, and have no lateral connexion. This condition of carti lage is said, by Sir B. Brodie, to be frequently, but not constantly, the first stage of ulceration ; and he conceives it may often exist where no ulceration is ever to follow. Mr. Key looks on it as " a disease of a. peculiar character." And we have frequently found it in the dissecting room, where there was not the slightest mark externally or internally of any other morbid action. The writer has observed it oftener on the patella than elsewhere ; and as this is so seldom the part first involved in the ulcerative process, it probably depends on an action of a different nature. The writer has also seen it oftener in joints long dead than in the more recent, and has therefore thought it might possibly be caused, in some cases at least, by the action of the synovial fluid, or by decomposition.
Secondary ulceration may commence in the bone or in the synovial membrane. (a).When the bone is previously diseased, that side of the cartilage which was turned to it is first affected. The adhesion of the two tissues is diminished ; we find it riaore easy to separate them. After some time a separation actually takes place, and a vascular net-work, sometimes a layer of granu lations, occupies the interval. The surround
ing cartilage is softened. The ulcer, with cha racters differing little from the primary form, goes on more or less rapidly, until an opening is made quite through into the cavity of the joint. When this opening is effected, the mat ter, which in this form of ulcer is always pre sent, finds its way into the synovial sac, and ex cites inflammation there.
The disease of the bone commonly giving rise to this ulcer is the slow strumous affection of the spongy extremities, so accurately de scribed by Sir B. Brodie, the symptoms of which are familiar to every surgeon. A more acute inflammation of the osseous tissue is oc casionally to be seen, and may be followed by a disease of the same nature, or differing only in the quickness of the course it pursues.
(b) Secondary inflammation extending from the synovial membrane is most apt to attack the edges of the cartilages in the first instance. These are thinned, as if abraded, and over lapped by the vascular or disorganized mem brane. The bone remains sound, as in the primary ulceration. For further particulars on the ulceration of cartilage, see JOINT.
Does fractured cartilage ever unite by cartilage ? It probably never does. The costal cartilages, when broken, unite by lymph, which soon after is converted in bone, but never appears to form true cartilage. When a fracture extends into a joint, as we often see in the condyles of the humerus and femur, the divided cartilage is united by a cicatrix, which is not truly car tilaginous. Neither does it appear that car tilage is ever regenerated. Laennec believed it was : " in examining a knee-joint, he found in the centre of the articulating surfaces, in place of the natural cartilage, a thin cartilaginous lamina, semitransparent, adherent to the bone ; the old cartilage formed around it a projecting border, as if fimbriated." This observation certainly was not enough to establish its power of regeneration. We often find in cases of gout and rheumatism, and especially in the disease designated morbus coxte senilis, that the cartilage is removed, and in its place a compact shining layer of osseous sub stance like ivory deposited. This is not owing to an ossification of the cartilage, for the cartilage is often found completely absorbed, and the rough bone exposed, which, if seen at a later period, would doubtless be covered with this deposit to prevent the disintegration of its cancellated structure.