When the disease begins with swelling, which is of a chronic character, and produces but little inconvenience, and when the more urgent symptoms supervene after the swelling has continued for a considerable time, there is every reason to suppose that the disease has originated in the synovial membrane, or perhaps in the osseous cancelli, and this is generally met with in poorly fed and strumous subjects. But when the first symptoms have been pain and stiffness of the joint, without change of its appearance, and when the swelling has occurred after these symptoms have been of some duration, then it is probable that the cartilages are the primary seat of mischief. For the most part, however, the symptoms have a general resemblance in most chronic affections of the joints, and all the apparatus is sooner or later involved. When the cartilage has been extensively absorbed, a grating sensation is felt in moving the articular surfaces of the bones upon each other. In consequence, also, of the softening and disorganisation of the lateral and other ligaments, the affected articulation at length becomes unnaturally loose, which is owing in some measure, also, to the muscles being wasted and paralysed from pain and disuse. At an earlier stage of the disease, the joint may be rigid from deposition of lymph into the contiguous cellular tissue, and contraction of the muscles.

Purulent matter not unfrequently collects in the substance of the bones, which in all cases ultimately become softened in a remarkable manner. In many subjects, without actual disease of the osseous tissue, the heads of the bones are so altered in consistence, are so deficient of earthy matter, as to be easily cut with a knife. It has been a matter of dispute, whether, in this affection, the articulating extremities of the bones are enlarged or not; and the supposition that they are always more or less increased in size, or hypertrophied, has arisen from the extensive effusion and indurated state of the soft parts being mistaken for this enlargement. In the first stages of the disease, they are seldom, if ever, enlarged; but when ulceration of the bone has occurred, new osseous matter is deposited to a greater or less degree in the neighbourhood of the ulcer,—an attempt by nature towards a cure, but too often an ineffectual one. The bones, in strumous subjects, are often much enlarged, from collection of purulent matter in their substance giving rise to a sort of spina ventosa. I removed the upper extremity of a boy lately on account of extensive disease about the elbow. The ulna to near the wrist was swollen enormously by purulent collections in its medullary canal. In cases when the whole of the articulating extremity of the bone is not enlarged, still that portion which is more immediately concerned in the articulation is often considerably expanded.

Frequently when the knee is the seat of the disease, the lymphatic glands in the groin are enlarged; and when the elbow or wrist joints are affected, there is often a similar enlargement of the glands in the axilla: such glandular tumours have not rarely been confounded with those accompanying malignant disease, and measures which were absolutely necessary for the salvation of the patient, have thus been delayed or neglected.

When the disease is extensive, and has endured for a considerable period, hectic fever supervenes, and is aggravated after the abscesses give way. The patient becomes much weakened and emaciated, and loses his appetite; the pulse is rapid, with night sweats, diarrhœa, &c.; and from a continuation of the hectic cause, the life is endangered. In some cases, however, the health is restored, and the disease abates spontaneously; in others, the disease is arrested, and a complete cure accomplished, by the careful employment of such means as will be afterwards mentioned.

The appearances produced by inflammation and consequent disease of the synovial membrane, are the following. In the first stage, the internal surface of the capsular ligament, and the rest of the synovial membrane, is found of a red hue, its formerly colourless vessels being now made apparent, from enlargement and consequent injection with a greater quantity of red blood; and the serum within the cavity of the joint is more abundant than in the natural state. When the disease has been of longer continuance, the membrane is found considerably thickened, its usual smooth glossy surface is destroyed, it is irregularly flocculent, and frequently of a light yellow colour.

The interarticular adipose tissue also seems to be increased in volume, from being infiltrated with a serous fluid, by the discharge of which the diseased bloodvessels may have attempted to relieve themselves. When the inflammation has been intense, or of long duration, lymph is secreted, and deposited on the external surface of the membrane, forming an intimate union between it and the ligaments, and producing thickening of the external apparatus. Or the lymph is also effused on the inner surface of the membrane, to which it adheres and becomes organised; this is generally accompanied by the formation of purulent matter; the organised effusion is often so extensive as to conceal almost the whole of the synovial membrane, excepting portions of its delicate reflexions which invest the articulating cartilages. By the lymphatic deposit, to a less degree, the folds also of the synovial membrane adhere to each other, whereby the motion is still farther impeded, and the pain, when attempted, increased. Occasionally the synovial membrane is found enormously thickened, much softened in texture, and of a brown hue, when the disease has been of a very chronic character. Along with these appearances, serum is generally found effused, in a greater or less quantity, into the cellular tissue exterior to the ligamentous covering. In cases in which the matter has formed and remained long within the cavity of the articulation, the synovial membrane and the ligaments become blended into one soft mass, the internal surface of which is lined with a thick coating of lymph, as in the case of common abscess. If purulent matter is effused externally, and communicate with the joint, the capsular ligament will be found to have ulcerated and given way at certain points, forming apertures, usually of small size, and with ragged margins.

All these appearances may exist without disease of the cartilages

or extremities of the bones; but generally they are also affected at the same time. At first the surface of the cartilage is slightly irregular and rough, and the change is not observed, unless on minute inspection. Afterwards the surface is marked with small depressions, which may be numerous, and are surrounded with irregular and somewhat serrated margins. They gradually increase in depth and extent, and the subjacent bone is ultimately exposed at one or more points, as here shown. Often the greater part of the cartilage is removed by absorption; the bone is exposed, opened out in its texture, softened, of an irregular surface, and in some places excavated, containing a thin ichorous fluid; the process of ulceration has also extended to the osseous tissue. Sometimes scales of cartilage of considerable size are either completely detached, having become dead, and been thrown off by the natural process, and are found lying loose in the cavity of the articulation; or they are all but separated, adhering by one or more very slender attachments.

The incipient stage of such disease may exist without the synovial membrane being much, if at all, affected; but when the ulceration has made farther progress, all the articulating apparatus is more or less diseased. It may be here remarked, that the synovial membrane may be affected for a long period, thickened portions may extend over the cartilages, and these may have lymph upon them and yet remain intact.