1. Excision of part or the whole patella in the dog results in progressive abnormalities consistent with advanced hypertrophic arthritis; the alterations are least in magnitude when the superior or inferior half of the patella is spared.

2. When these alterations are severe, pain and dysfunction result.

3. The regions of the joint most severely affected are those comprising the patellofemoral joint.

4. It is reasonable to assume that the changes are the result of abnormal friction of soft tissues against cartilage and bone and impairment of the mechanism whereby the articular cartilage on the anterior surface of the femur is adequately nourished.

5. It is reasonable to assume that similar alterations in the configuration of the knee joints of other animals, including man, may be followed by similar changes. However, the differences in anatomical construction of the knee joint of the dog and that of man preclude accurate assessment of the severity of such alterations.

6. Whenever possible, the patella or at least its superior or inferior pole should he preserved, and that in those instances in which deletion appears mandatory, new methods should be designed whereby the normal mechanics of the joint are restored.