Diagnosis is to be based largely on the variability of the lameness at different times, its propensity to shift from place to place, its manifest association with exposure to cold, and with the immanence of electric storms or change in the barometric pressure, and its improvement under genial weather, warmth and comfort.
SYMPTOMS OF MUSCULAR RHEUMATISM IN HORSES.
Under usual causes, muscles tender, stiffness, groaning, loins, quarter, shoulder, neck, chest.
Developed under conditions similar to those causing rheumatism of the joints, rheumatism of the muscles tends to attack those of a particular region, and to continue in these throughout the attack rather than change to others. The affected muscles are very tender to the touch, but usually show no swelling nor heat. The muscles are relaxed and tend to atrophy, fever is little marked, there is comparatively little tendency to the implication of the heart, and the suffering and stiffness vary with the variation of the weather, or with electric or barometric changes. When generalized, however, fever may supervene, and the joints may be implicated (Thompson).
When the loins are affected they become extremely tender to the touch, and the horse shows great stiffness, and groans when made to walk and above all when turned or backed. He does not, however, show the unsteadiness in gait and tendency to stagger that is shown in sprain of the loins, and there is no history of a slip, fall or injury, but an unmistakable connection with cold, exposure, change of weather, or overfeeding on grain.
When the gluteal muscles are attacked there is intense lameness, and dragging of the hind limb, with an acute sensitiveness of the skin of the region, which characterizes neither disease of the hip nor of the trochanterean bursa.
When the scapulo-humeral muscles are the seat of disease, there is a marked stiffness, shortness of step, drooping of the head, and great tenderness of the skin and muscles to manipulation or the use of the currycomb. Like the other cases named it occurs suddenly, without evidence of accident, but bearing a relation to cold or other change of the weather, and is better or worse as the weather is more or less genial.
When the cervical muscles are affected (torticolis), the same features are noted, the absence of traumatic cause, the presence of a meteorological one, or at least of cold or wet, the responsiveness of the disease to the state of the weather, and to revulsive agents applied to the part. The neck may be held rigidly in one position, to one side or elevated so that there is great difficulty in getting the nose to the ground.
The costal muscles are less frequently attacked (pleurodynia), but the same general principles guide in diagnosis.
Seidamgrotzky alleges the constant existence of acidity of the urine in muscular rheumatism. This may be attributed to the active trophic changes going on in the muscles.