In this disease we recognize a local expression of a constitutional disorder arising out of some as yet undefined noxious principle in the blood.

Aged animals are more especially its victims, but it sometimes also affects the young.

In the former it assumes a chronic type, while in the latter the attack is more frequently of the acute variety.

Causes

These are predisposing and exciting. Most if not all subjects of this affection inherit a constitutional condition which predisposes them to suffer when exposed to one or another of the various exciting causes. Of these the principal are exposure to wet, and cold easterly and northeasterly winds, hard and continuous work, sprains, concussions, blows and other injuries to the joints, influenza, and strangles.

Symptoms

The disease may be confined to a single joint, but more often it invades two or more. The large joints, as the knee, the hock, the stifle, and the fetlock, are those most frequently involved. In its chronic form rheumatic arthritis commences with stiffness, observed more particularly after exertion. For some time it may continue without materially interfering with the animal's movements. Then a slowly progressive enlargement appears - at first resulting from distension of the capsular membrane with synovia, but later the bones of the joint throw up irregular nodular swellings around and about their articular ends, and these, encroaching on and irritating the surrounding ligaments and tissues, provoke additional enlargement. Pain and lameness are now more or less marked, and the action of the affected joint becomes not only restricted but difficult.

In long-abiding cases the cartilage may be removed from the articular ends of the bones, whose rough surfaces, when brought into contact with each other, impart to the hand and the ear a crepitating sensation or sound. In this disease there is no tendency to the formation of abscess, but the morbid action is expended in provoking enlargement and condensation of the extremities of the bones and tissues connected with the joint.

Treatment

In this connection much importance attaches to an early recognition of the disease, when a dose of physic, followed by a short course of iodide of potassium, and a brief rest, will usually check its progress. Where it has been allowed to advance so far as to produce considerable swelling, massage and friction should be freely applied to the joint two or three times a day, and in the intervals it should be enclosed in a warm flannel bandage. The food should include a liberal amount of carrots or other succulent roots or grasses, with bran and a small ration of scalded corn and sweet hay.

With this may be given an ounce of linseed-oil night and morning, with a full dose of iodide of potassium and carbonate of potash. If the joints are very painful they may be anointed with belladonna liniment twice a day. Should this not have the desired effect, a mild iodine blister repeated at short intervals may yield good results.

Horses giving evidence of this affection should have a dry lair and be protected as far as possible from cold and wet, especially while heated.