The origin of degenerative joint disease development in the scapulohumeral joint may be a traumatic event or develop slowly over a period of time. It is almost exclusively diagnosed in ponies and Mini Shetland ponies.
The animal shows a chronic lameness and, in long standing cases, partial atrophy of the shoulder muscles. The animal shows a shortened protraction phase of the limb during walking.
Radiographs usually show the nature of the problem.
The craniocaudal view (left) depicts a defect in the humeral joint surface which is presently occupied by the medial edge of the glenoid resulting in a subluxation of the joint.
The lateral view (right) shows superimposition of the scapular and humeral joint surfaces (arrow).