Osteochondrosis is a disease that affects the joints of young horses, pigs and dogs.
In a normal, healthy joint, a thick layer of cartilage lines the joint surface, allowing smooth movement for the ends of bones to glide past each another. A thick layer of bone is normally located immediately below this joint cartilage. The bone in this area supports the overlying cartilage and distributes concussive forces generated from movement.
In young animals, the junction between cartilage and bone functions as a growth plate and is essential for allowing the bone to grow in length and diameter.
Osteochondrosis develops when the bone underlying the joint cartilage doesn’t properly form during growth. The cartilage is unsupported and with time and activity, becomes damaged.
In the worst manifestation of this disease, the joint cartilage cracks through completely, creating large flaps that detach from the underlying bone. The flaps themselves, and the small pieces that break off, can get in the way of normal joint movement. And when the disease is this severe, it becomes extremely painful with animals limping as a result.
The severe cartilage damage sets up a vicious cycle of inflammation within the joint that further destroys the remaining cartilage and can progress to arthritis.
The cause of this disease in animals is not completely understood. Some type of disruption to the blood supply to the bone under the joint cartilage during growth is thought to be a main underlying mechanism.
In horses, diet has been also implicated as a contributing factor. Young horses fed high carbohydrate diets and diets that are deficient in certain minerals seem to have higher rates of this disease.
Other contributing factors include fast growth rates in young animals and repeated trauma to the joint, which can occur with activity.
In dogs, large and giant breeds can be affected and in pigs, it affects those lines that are selected for rapid growth.
Osteochondrosis is also a possible cause of wobbler syndrome, where the neck vertebrae are improperly formed and movement pinches the spinal cord, causing neurological disease.
Many animals have mild changes to the bone but these do not necessarily progress to severe disease. Horses with cartilage damage may have joint swelling, show lameness and have reduced mobility. Diagnosis is based on the breed, clinical exam and X-rays.
In horses and dogs, mild, early cases are treated with supportive care, often with good success. Confinement to a small pen or stall will limit exercise and minimize damage to the joint, allowing time for healing to occur.
Growth can be slowed by restricting feed and in some cases, supplementation to correct mineral deficiencies may help. Severe cases can be treated surgically by removing damaged cartilage to allow healing. This is done using an arthroscope, a small instrument with a camera that is inserted into the joint.
In pigs, mild cases can be treated through management such as adequate bedding to prevent slips. Severe cases are often culled because lameness can be a serious welfare concern.
Because the exact cause is not completely understood, it is challenging to assess the effect of preventive measures. Some experts suggest that young, rapidly growing dogs and horses should be kept on a lower plane of nutrition to keep growth rates at a reasonable rate.
Due to the suspicion of a genetic component, animals with severe osteochondrosis should not be bred to reduce the risk of passing along this disease.
Dr. Jamie Rothenburger, DVM, MVetSc, PhD, DACVP, is a veterinarian who practices pathology and is an assistant professor at the University of Calgary’s Faculty of Veterinary Medicine.