Small, hard, pea like, subcutaneous nodosities were first noticed by Floriep, in 1843, in rheumatism in man, and have been met with in different cases in the horse. Rodet fils met with great numbers of these nodules crepitating under pressure, in a horse that had suffered for months from chronic rheumatism.
Acute pain on moving the affected joint or tendon is a most characteristic symptom. The horse goes dead lame, walks on three legs, or with great stiffness, and avoids as far as possible all flexion of the joint. If left alone the animal stands stock still, never moving from the place, or in the worst cases lies down and refuses to rise. If compelled to walk his suffering is shown by hastened breathing, dilated nostrils, anxious, pinched countenance and low plaintive neighing. The affected joint is held semi-flexed, to relieve the tension, the pastern is habitually more upright, and if the foot is lifted and the affected joint bent or extended, the animal winces, or resists, and tries to draw away the limb and groans. The movements of the affected joint in walking or under manipulation, are often attended by cracking which may be both felt and heard. It has been variously attributed to lack of synovial lubrication (Cadeac), and ulceration of the articular cartilage (Lafosse), yet it may occur from the constrained position assumed, as in the case of a man attempting to walk noiselessly on tip toe, and in other cases from the extension of false membranes, or of rigid or contracted binding ligaments.
Rheumatism of the fetlock and sesamoid pulley, as the most common form in solipeds, demands a special notice. The swelling of one fetlock, of the two fore, of the two hind or of all four at once, extends beyond the limits of both joint and sesamoid pulley and may form a general engorgement or stocking which serves to hide the synovial distension. Pressure however shows that while all is tender, the extreme tenderness is referable to the joint, the synovial sheath of the flexors, to the flexors or suspensory ligaments. As the general swelling subsides the rounded or ovoid synovial distensions become more patent. The swelling and tenderness may extend to the knee in which case the synovial membrane of the carpal arch is especially distended and tender from the carpus down, or in the hind limb the synovial membrane of the tarsal arch is distended showing in this case on the inner and outer sides in front of the calcis, and not infrequently implicating the summit of that bone as a capped hock.
In rheumatism of the shoulder the coraco-radial tendon and pulley may be involved, causing a diffuse swelling on the point of the shoulder. If the hip is the seat of disease the median gluteal may suffer, causing an indefinite swelling over the joint. If the stifle is affected the patellar capsule suffers and not infrequently the tendon and pulley of the flexor metatarsi are involved.
The most important internal complications, pericarditis and endocarditis, are manifested by their usual symptoms, sharp, variable, irregular, unequal or intermittent pulse, blowing murmur usually with the first heart sound, oppressed breathing, and it may be muffled heart sounds, or dropsies.
Course. This is exceedingly uncertain. Some cases make a rapid progress to complete convalescence; others make partial improvements interrupted by relapses; others have the morbid process subside in great measure in one joint or organ only to reappear in full force in another; others leave complications on the part of the heart especially and are rendered permanently useless. Even should the heart escape, the health often suffers so much in connection with the destruction of the red globules, the malnutrition, and the local disease, swellings and distortions of the joints that a perfect recovery seems distant and problematical.
SYMPTOMS OF CHRONIC ARTICULAR RHEUMATISM IN THE HORSE.
Larger joints, muscles, heart, false membranes, indurations, thickenings, calcifications, remittent, weather changes, cold, damp beds, winds, open windows or doors, draughts, cold sponging, clipping. Diagnosis: lameness variable, shifting, electric and meteoric storms.
Chronic rheumatism may be a sequel of the acute, or it may occur from the same causes acting with lessened force, or on a less susceptible animal. It tends to attack the larger joints especially, though it may implicate the muscles as well. Coincident affection of the heart is less common than in the acute, and when it does arise seems to advance slowly. It is liable to cause permanent distensions of the affected joint capsules, as well as false membranes, articular abrasions, degenerations and ulcerations and less frequently bony enlargements and calcifications, the latter implicating the soft tissues in the vicinity.
The attendant lameness is liable to be remittent or intermittent, subsiding in warm buildings and during genial, clear sunny weather, and relapsing in connection with cold, raw nights and mornings, exposure in the dew or rain, and before and during great changes of weather. Cold, damp beds, chilling draughts between open doors or windows, washing with iced water, sudden intense cooling of the body after perspiration, clipping during cold weather, any cause of sudden rigor, when followed by stiffness, lameness and articular swelling, serves to identify the latter as rheumatic. Even the warmth induced by judicious exercise, may cause improvement, so that a horse, starting out stiff or lame, may drive out of it after going a mile or two. The formation of subcutaneous nodules, though rare, appears to be more frequent than in acute rheumatism.