Osteochondritis Dissecans (OCD)

What is OCD?

OCD is a condition that occurs in growing puppies of larger breeds, mainly between the ages of 4-9 months, but can occur as late as 12 months or possibly a little older. It is most normally seen in the shoulder joint but can be seen in stifles, elbows, hocks or other joints. In roughly one third of the cases of OCD, the disease is bilateral (in both joints). Sporadically it is present in several different joints in the same individual. It is seen twice as often in males as in females.

OCD is considered to be caused by a problem in the growth rate of the joint cartilage relative to the underlying subchondral bone. The cartilage over the bone in the joint becomes thickened and the growth of the underlying bone is transformed, because the joint is an area of movement and stress, this thickened cartilage is at risk of being torn, particularly in the areas most subjected to trauma, stress and movement, such as the caudal area of the shoulder joint. When repeated trauma causes a flap of cartilage to tear away from the underlying bone, the condition becomes OCD. Because of the tear, the joint fluid can come in direct contact with sensitive areas of the now-exposed underlying bone and can cause pain. Lameness will typically be present in the dog at this time. If the cartilage flap remains attached, it will not re-attach and heal back into its original position. If the cartilage flap tears completely loose from the adjoining cartilage, it becomes a loose body in the joint called a "joint mouse". Once the flap has detached, the torn area where the flap originated typically heals when the lesion is filled in with fibro cartilage, a type of "scar" cartilage. Joint mice may float around in the joint, ultimately being broken down and absorbed, or they may be nourished by the joint fluid and grow to a larger size than the original loose cartilage body. Possible complications arise when joint mice attach themselves to other areas in the joint or become entrapped in the bicipital tendon sheath, causing irritation, obstruction of movement and pain. The breakdown of cartilage from these various processes may cause swelling pain and the eventual development of secondary osteoarthritis in the affected joint.

Is it inherited?

OCD is considered to be a common disease in large and rapidly growing breeds of dogs, with most affected breeds averaging over 27kgs. However, some medium breeds, such as the Border Collie also have a high occurrence rate of this disease. Although the factors that cause OCD are not completely determined, 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 behaviour, which are also influenced by inheritance. Therefore, the genetic link for most types of OCD is considered to be indirect, that is, an inherited tendency. Certain areas for OCD lesions, such as the elbow, appear to have a greater direct genetic contribution and a higher heritability than other areas, such as the shoulder. The most important contributing factor in OCD of the shoulder, the most common area, is thought to be trauma.

Border Collies have a higher occurrence of OCD than might be expected for their size and the weight bearing stress on their joints. It would seem likely that behavioural characteristics common to Border Collies could contribute to the increased occurrence of OCD in this breed. The high energy levels, athletic ability, stamina and quick reflexes for fast turns and speed changes that Border Collies possess, could predispose them to trauma and stress in joints that most other breeds of similar size would not commonly experience. The overall increased occurrence in males for this disease is thought to be due to the increased growth spurt in the male around the susceptible time period for OCD development. It is tempting to speculate that behavioural factors common to males might also be involved in this increased susceptibility.

How can it be prevented?

As in many other developmental skeletal problems, an imbalance of calories, protein and nutrients can increase the occurrence of OCD. In general, rapid weight gain in puppies at the crucial time period between 4-9 months predisposes larger breed dogs to OCD. High intake of calcium and protein has also been implicated in the development of this condition. Therefore, care must be taken in feeding young puppies special "growth formula" puppy foods or high protein diets.