Post natal development of the canine elbow joint: a light and electron microscopical study.

The elbows of 13 puppy cadavers were dissected, samples were taken for light and electron microscopy, and the thickness of the articular cartilage of the distal humerus and proximal ulna was measured. Throughout post natal development differences were found in the arrangement of the growth plate and articular chondrocytes. At birth, the articular surface had remnants of a fibrous limiting membrane that was continuous with the perichondrium, a finding not previously recorded in dogs. Orientation of the collagen fibrils within the matrix of the articular cartilage was initially lacking but became established by three weeks. In the humerus cartilage canals were present up to 12 weeks old. The articular cartilage of the humeral condyle varied in thickness across the joint surface, being thicker on the medial than on the lateral side; it was also thicker at the apex of the medial coronoid process. These regions of thick cartilage correspond with the sites where cartilage defects arise in elbow osteochondrosis. No histological evidence was found that the medial cornoid process of the ulna is a separate centre of ossification.