h, 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