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.
_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.