OCD is a condition that occurs primarily in puppies between the ages of 4-9 months, but can also be found in older puppies. It is considered to be a common disease in rapidly growing dogs of large breeds. However, medium breeds such as the Border Collie can also have a high incidence of this disease. It is seen twice as often in males as in females. The shoulder joint is the most commonly affected site but it can be seen in stifles, elbows, hocks or other joints. The diagnosis is usually confirmed by x-ray of the involved joints. In approximately one third of the cases of OCD, the disease is bilateral (in both joints). Occasionally, it is present in several different joints in the same individual. OCD is thought to be caused by a problem in the growth rate of the joint cartilage relative to the underlying subchondral bone. Although the factors that cause OCD are not completely understood, direct factors considered to be involved in the development of OCD are rapid growth and trauma to the joint. Indirect factors affecting rapid growth include nutrition, hormones, and genetic predisposition to rapid growth and large size. Indirect influences that may lead to increased trauma to the joint include conformation and behavior, which are also influenced by heredity. Therefore, the genetic link for most types of OCD is considered to be indirect, that is, an inherited tendency. Certain sites for OCD lesions, such as the elbow, appear to have a greater direct genetic contribution and a higher heritability than other sites, such as the shoulder. The most important contributing factor in OCD of the shoulder, the most common site, is thought to be trauma. OCD can best be prevented in growing puppies by controlling the main precipitating factors, over nutrition and activities that could result in injury to the joints. Because factors involved in the heritability of OCD are considered to be indirect, and therefore not easily controlled by selection, ABCA has no breeding recommendations for OCD at this time.