Arthritis.

The study of arthritis in the horse is limited to a consideration of joint inflammations which, for the most part, are of traumatic origin.  Unlike the human, the horse is not subject to many forms of specific arthritis—­tubercular, gonorrheal, syphilitic, etc.

A practical manner of classification of arthritis is traumatic and metastatic.

Traumatic arthritis may result from all sorts of accidents wherein joints are contused.  Such cases may be considered as being caused by direct injuries.  Instances of this kind, depending on the degree of insult, manifest evidence of injury which ranges from a simple synovitis to the most active inflammatory involvement of the entire structure and adjacent tissues.

The reactionary inflammation which attends a case of tarsitis caused by a horse being kicked is a good example of the result of direct injury.  Such cases, if the contusion is of sufficient violence, result in arthritis and periarthritis.  In inactive farm horses, during cold weather, this condition becomes chronic, swelling remains for weeks after all lameness and pain have subsided and occasionally hyperthrophy is permanent.

Arthritis occasioned by indirect injury, such as characterizes joint inflammation from continuous concussion, is seen in horses that are worked at a rapid pace on city streets or other hard road surfaces.  Such affections may be acute, as in some cases of spavin, but are usually inflammatory conditions that do not occasion serious disturbance when these affections become chronic.  If the involvement persists with sufficient active inflammation, there may follow erosion of cartilage and incurable lameness.  If extensive necrosis of cartilage takes place, the attendant pain will be sufficient to cause the animal to favor the diseased part and such immobilization enhances early ankylosis—­nature’s substitute for resolution in this disease.

Wounds invading the tissues adjacent to joints, when these wounds are of considerable extent, cause inflammation of such articulations by contiguous extension of inflammation.  As long as an injury remains practically aseptic, or if infected and the septic process does not involve the joint proper by direct extension, no more serious disturbance than a simple synovitis will result.  If, instead, a periarthritic inflammation is serious or destructive in character, the type of arthritis will be grave—­even though due to an indirect cause.

Where a vulnerant body penetrates all structures and invades the interior of the joint capsule the result is that a more or less active disturbance is incited.  The introduction of a sterile instrument into a joint cavity, under strict asepsis, where a perfect technic is executed, does not cause perceptible manifestation of the injury, if the opening so made is small—­such as a suitable exploratory trocar makes.  But a puncture made in a similar manner and with the same instrument without due regard to asepsis is likely to cause an infectious synovitis and arthritis usually follows.