As a rule, complete disarticulation immobilizes the affected joint and
in most instances there is noticeable an abnormal prominence in the
immediate vicinity--in patellar luxation, the whole bone. In other
instances the articular portion only, of the affected bone is
malpositioned. Usually, luxation and fracture may be differentiated in
that there is no crepitation in luxation and more or less crepitation
exists in fracture.

It is evident, when one considers the symptomatology and nature of the
affection, that fixed luxation is usually caused by undue strain or
violent and abnormal movement of a part. Joints having the greater
freedom of movement are apt to suffer luxation more frequently.


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