Part 95

The articular cartilages and the fibro-cartilages may be the seat of congestion, with ramified or uniform redness, and areas of swelling, softening, absorption, erosion and ulceration, the ulcers varying in size from a millet seed upward. The nuclei increase in size and the cartilage cells multiply. In chronic forms calcification is not uncommon.

The articular lamella and subjacent bone may show inflammation with increased vascularity, softening and even ulceration. In the chronic forms on the parts denuded of cartilage, the surface of the bone may show the clear, polished condition known as eburnation.

The binding ligaments may show congestion, thickening, exudation, softening, with increased rigidity, or in some cases relaxation. Calcification is not uncommon in chronic cases. The soft parts around the joints are often extensively infiltrated and swollen.

In horses these lesions are specially common in the fetlock, but occur also in the knee, elbow, shoulder, hips, stifle and hock. In cattle they tend to attack the same parts with a preference perhaps for the hocks and fetlocks.

Changes in the blood. The blood becomes profoundly altered, the albumen reduced, the fibrinogenous elements increased (5 to 10 parts per 1000 instead of three), the red blood globules disappear (in man 2,850,000 per cubic millimeter instead of 4,500,000), the hæmoglobin and oxidizing power of the blood are reduced by about 50 per cent., the leucocytes are relatively increased, and coagulation takes place with unusual firmness, a cupped surface and an excess of buffy coat. No excess of urea, uric acid, nor lactic acid, has been found, nor has acidity been found save in very rare cases. In rare and severe cases petechiæ have appeared on the skin and mucosa.

Lesions of the heart. The implication of the fibrous structures of the pericardium and heart and especially of the valvular structures is a common lesion, and to be dreaded more than all others. In all animals this tendency to cardiac lesion is well marked, but especially in solipeds in which the great demands made on the heart during rapid paces, heavy draught, jumping, etc., severely strain the cardiac mechanism. In dogs there is not only the violent exertion and high blood pressure, but also the great irritability of the nervous mechanism presiding over the heart and the tendency to irregularity and intermissions in the rhythm and palpitations even when the organ is sound. There is every reason to conclude with Trasbot, Megnin, Heu and Laurent that in many cases the heart is primarily attacked, and that this heralds the articular rheumatism. In other cases undoubtedly the cardiac affection is secondary, following the articular attack.

Endocarditis is the most frequent, being found in a large proportion of fatal cases, and thickening of the valves, wart-like exudates and coagula are especially common. The clots may fill nearly the entire ventricular cavity, or at times the auricular, and show a preference for the left side, probably because of the more vigorous systole and the higher blood tension. The clots as a rule are firmly adherent to the diseased valve. Ulceration of the valve is rare in rheumatism. Other parts of the ventricular endocardium may be involved, becoming red, congested, rough or thickened, with adherent blood clots.

Pericarditis is less common though it may exist on either or both the cardiac and visceral folds. It is shown by vascularization, thickening, fibrinous exudate, and serous effusion. Haycock found in a horse a quart of reddish serous exudate with floating fibrous shreds and false membranes. Pus has been found in exceptional cases manifestly indicating a complex infection. Like endocarditis it may precede, follow, or coincide with an articular attack (Leblanc, Cadeac).

Myocarditis is usually seen as a complication and extension of rheumatic inflammation of the visceral pericardium, or of the ventricular endocardium. The muscular tissue may appear parboiled and friable, and shows granular or fatty degeneration.

Pulmonic and pleuritic lesions. Embolism of the lungs and pleura may occur from the transference of clots from the right heart, yet the sequence is much more commonly an articular rheumatism following infective disease of the lungs. Cadeac suggests that the impaired nutrition in pneumonic and pleuritic animals predisposes to the rheumatic arthritis, and again that the microbes of the infectious chest affection, colonizing the joints and other synovial sacs, determine the rheumatism. This last theory has the weakness of identifying influenza and contagious pneumonia with articular rheumatism, and is negatived by the experience that these two pulmonary affections never develop de novo from simple rheumatism. The rheumatism which follows influenza and contagious pneumonia therefore must either be considered as a pseudo-rheumatism, or a rheumatism occurring only concurrently and accidently with the pulmonary affection. Apart from this, pleurisy or even pneumonia occurs as a simple extension from a rheumatic pericarditis.

The occurrence of the rheumatoid affection as a complication of influenza and contagious pneumonia in the horse, usually appears not earlier than 15 days after the outset of the pulmonary affection and may be delayed, according to Palat, for 102 days. Palat who had excellent opportunities for observation in army horses found that about one in ten was the ratio in which the rheumatic affection followed these pulmonary diseases.

The pulmonary lesions in these affections are essentially those of uncomplicated influenza, or contagious pneumonia.

Cerebro-Spinal Lesions. Nervous disorders are occasionally seen in rheumatism in man (dullness, prostration, delirium, coma, spasms) and traced in different cases to hyperthermia, congestion, exudation, embolism and toxins. In a few cases in the horse, cerebral complications have been observed. Olivier saw a horse with lachrymation, closed eyelids and hot, tender forehead, which showed at the necropsy articular inflammation, and sanguineous effusion in the cranium, encephalon, frontal and maxillary sinuses and ethmoid cells. Jacob records two cases (mare and horse) in which rheumatism was complicated by meningo-encephalic congestion but without necropsy as both recovered.

Digestive system. In man rheumatism has been exceptionally preceded by pharyngitis, dysphagia, and diarrhœa. In the horse Haycock has seen concurrent congestion of the pharyngeal mucosa, Olivier congestion of the stomach and intestine, and Jacob diarrhœa and abdominal pain, Leblanc and Palat record cases of peritonitis accompanying articular rheumatism in the horse.

SYMPTOMS OF ACUTE ARTICULAR RHEUMATISM IN THE HORSE.

Chill, hyperthermia, lameness in fetlock, hock, knee, shoulder, stifle, hip, elbow, tendons, sheaths, bursæ, bilateral, shifting, swelling, heat, tenderness, decubitus, joint semi-flexed, pain on extension or flexion, signs of cardiac disease. Course: rapid to recovery, improvements and relapses, metastasis, debility.

The attack is usually sudden and marked by a slight chill, shivering or staring coat with hyperthermia and lameness. The temperature may vary from normal to 107° or 108° F. in severe attacks. In many cases the fever and lameness appear simultaneously, the former being in ratio with the extent and severity of the latter, but not infrequently the elevation of temperature precedes the articular symptoms, and then it is to be considered as concurrent with the internal lesions—cardiac, pericardial or otherwise. In other cases the articular lesions and lameness precede by several days the appearance of the fever. So far as we know the fever never antedates the occurrence of some local lesion, external or internal.

The joints affected are very varied. The fetlock is the most frequently attacked, but some of the other larger joints, the hock, knee, shoulder, stifle, hip and elbow are often involved or exclusively affected. The adjacent tendons and their synovial sheaths are very often implicated; the attack is very prone to show a bilateral symmetry, the same joints (right and left) on the corresponding fore or hind limbs, suffering at once, or, as in the case of the fetlocks, all four are simultaneously attacked. A joint that is weak by reason of previous injury or disease is especially liable to suffer, and is then less likely than joints that had been previously healthy to undergo speedy improvement. When the symptoms wander from joint to joint or from joint to muscle, or fascia or tendon, the disease in its earlier seat seeming to undergo almost complete resolution, while it advances with great intensity in the newly affected joint or part, the occurrence is highly significant. These transitions often take place with great rapidity. Thus the centre of suffering may shift from one joint to another in an hour, (Megnin, Cadeac), or from a limb to the loins in a quarter of an hour (Lewis). The fact that the inflammation remains fixed in one or several joints, is not, however, proof of the absence of rheumatism. A joint with a primary weakness or injury may remain the seat of disease through even a chronic rheumatism.

The affected joint is usually swollen, hot and tender; the tenderness being as a rule greatest where the capsular ligament is pressed upon. These symptoms are very evident in joints that approach the surface, and obscure in such as are thickly covered by muscle (shoulder, hip). The swelling is soft, or tense and elastic (especially over the synovial membrane), or œdematous and pitting on pressure. On white skins sparsely covered by hair there is marked redness and congestion, the veins standing out prominently and the arteries above the joint pulsating strongly. When the tendinous sheaths are involved, they stand out as elastic lines following the course of the tendons, and with more or less pasty swelling adjacent.

In some cases, however, the swelling may be entirely absent, and the trouble is to be located only by the local tenderness and pain during motion.

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.