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.