Etiology and Occurrence.—­Inflammation of the scapulohumeral articulation results from injuries of various kinds, including punctures which perforate the joint capsule, bruises from collars, metastatic infections and involvement as a result of direct extension of infectious conditions situated near the joint.

Classification.—­Acute arthritis may be septic or aseptic, and there seems to be a remarkable tendency for recovery in cases of septic arthritis involving this joint in the horse.

Chronic arthritis with destruction of articular surfaces and ankylosis, is seldom observed.  It is only in cases of severe injury, where the articular portions of the bones are damaged at the time of infliction of the injury, and where the articulation remains exposed for weeks at a time, together with immobility of the parts because of attending pain, that permanent ankylosis results.

Scapulohumeral arthritis may result then from infections, local or metastatic; from injuries, such as contusions of various kinds; from wounds, which break the surface structure or perforate the joint capsule; or from luxations.

Infectious Arthritis.

Infectious arthritis of the scapulohumeral joint the result of local causes other than produced by septic wounds, seldom causes serious inconvenience to the subject.  Where such occurs, however, there is manifested mixed lameness and complete extension of the extremity is impossible.  Local swelling is present and manifestations of pain are evident upon palpation of the affected area.

Treatment.—­During the first stage of the infection, local applications, hot or cold, are indicated.  A hot poultice of bran or other suitable material contained within a muslin sack, may be supported by means of cords or tapes which are passed over the withers and tied around the opposite fore leg.  Such an appliance may be held in position more securely by attaching it to the affected member.  Following the acute stage of such an infection, any local counter-irritating application or even a vesicant is in order.

Where abatement of the infectious process does not take place, and suppuration of the structures in the vicinity of the joint occurs, it is necessary to provide drainage for pus.  In some cases of strangles, for instance, large pus cavities are formed and drainage is imperative.  However, metastatic inflammation of this joint is seldom observed except in cases of strangles.  The animal should be kept perfectly quiet until recovery has taken place.

Injuries.

Injuries to the scapulohumeral joint may be the result of kicks, runaway accidents or bruises from the collar, and there may result, because of such injuries, reactionary inflammation which will vary in intensity from the mildest synovitis to the most severe arthritis, causing more or less lameness.

Treatment.—­The general plan of treatment in this form of arthritis is the same as has been outlined under the head of infectious arthritis, with the exception that there is seldom occasion to provide for drainage of pus.