Anatomy of Canine Shoulder Disorders

Canine shoulder problems are relatively common and include Osteochondritis Dessicans (OCD) instability and biceps tendon disorders. Instability and bicipital tenosynovitis occurs in middle to older aged dogs (Labrador retrievers are the most common breed affected). Canine OCD is the most common problem and occurs in young (8-12 month old), large to giant breed dogs.

Osteochondrosis is a failure endochondral ossification. A region of cartilage which was destined to turn to bone, does not. Thus, a focus of overly thick cartilage remains (versus the surrounding joint surface cartilage)(fig. 1). The deepest layer of this thickened cartilage is inadequately nourished from joint fluid (squishing into cartilage with weight bearing), dies, and detaches from the underlying bone (fig. 2). Eventually this fissure propagates to the joint surface and a “flap” develops (dessicans)(fig. 3). Cartilage debris and inflammatory mediators are released into the joint fluid and inflammation ensues. With time, arthritis/degenerative joint disease occurs.