OCD is a degenerative bone disease that is found in many types of animals, including horses. Osteochondritis dissecans or OCD is most commonly associated with younger horses that are rapidly growing and developing, and is also typically associated with horses that have longer leg bones. Longer leg bones means taller horses, so usually breeds that have a mature height of over 15 hands are more prone to OCD but it can also be seen occasionally in smaller and shorter horses. What is interesting is that there seems to be no difference between the tall heavy horses and the tall lighter horses, so weight itself is not the key factor, it is the length of the bones.
In normal growing horses the ends of the bones that meet up at the joints are soft and this is where the growth occurs. As the cartilage becomes hard it adds to the length of the bone, resulting in growth. In horses with OCD the softer, growing ends of the bone do not harden, rather they stay soft and actually begin to break down, resulting in pain, swelling and lameness that may seem initially to move throughout the limbs.
The resulting problems with the joints include the formation of large numbers of bone chips in the joint, bone on bone wear and bone cysts or OCD lesions. The constant damage and stress on the joints will lead to arthritis and problems with degenerative orthopedic disease (DOD) as the horse matures.
Researchers have determined that the problem is most pronounced in rapidly growing and maturing lines of horses and those that are fed diets that are overly high in protein, energy and fats often are associated with greater likelihood of OCD. This is also true if the mare is fed high levels of supplements and minerals during the pregnancy. An animal nutritionalist can evaluate your feeds and supplements and help you balance the feed for both mares and foals, especially in the larger breeds of horses.
The most common signs of OCD will be painful movement or swelling and pain in the joints that moves from leg to leg and seems to be more problematic at times and then disappear, only to come back at a later time. This waxing and waning of the pain may or may not be more pronounced with additional exercise. Often the joints will seem puffy and will feel hot to the touch. The colt or filly may constantly shift their weight from leg to let or may seem to be stiff and sore throughout the day. Diagnosis is usually confirmed with x-rays and endoscopy to identify soft tissue at the end of the bones and any OCD lesions that may have formed.
Treatment for OCD lesions may include changing the feed and supplementation to slow rapid growth, monitoring and limited exercise and careful management of the young horse with anti-inflammatories. In severe cases surgery may be required to remove bone chips or reconstruct the joint if the damage is severe.