Hypothesis 2

Abnormal Ossification of Articular Cartilage

Jocelyn is a 9 month old rottweiler who is allowed to free feed a large breed food.  This increase nutritional supply is allowing the cartilage to grow at a faster rate than it can be ossified.  This  leads to the articular cartilage of a joint becoming thicker than normal because the endochondral ossification does not keep pace with the cartilage growth.  The vascular supply can not support the deep layer of cartilage, so it dies.  Necrosis of the deep layer of the articular cartilage keeps the surrounding cartilage from being able to mineralize.  This leads to a thickened layer of cartilage around the joint.  It is possible for the cartilage to tear away from the bone causing a flap or a joint body in the joint space.  This results in joint pain. .The healing of the joint body results in granulation tissue and fibrosis which can lead to a reduction in joint mobility.

We would expect to see a  lameness or a gait abnormality that persisted for weeks or months in an animal with this problem.  This is normally a unilateral lameness.  Jocelyn has a bi-lateral hindlimb lameness that has been ongoing for two weeks.  The lameness in Jocelyn is more pronounced in the right hind limb and it may be possible that the apparent lameness in the left hindlimb is a result of compensation.

In radiographs of a dog with this condition we would expect to see irregular subchondral cartilage with different levels of mineralization around the bone.  It may also be possible to see a flap of cartilage or a joint body.