Conditions or ailments that are the cause of a problem that you see - your observation.

Your vet may diagnose

Osteochondrosis, OC, Osteochondritis Dissecans, OCD


Development of the limb bones in a young horse requires a soft, cartilage template be converted to bone, a process known as endochondral ossification.

Osteochondrosis (OC) generally refers to the abnormal transformation of this cartilage template to bone. OC/OCD is a common developmental disorder and seen most commonly in young horses. It is an orthopedic disease of the bone-cartilage junction under the joint surface that damages the cartilage on the joint surfaces.
Osteochondritis Dissecans (OCS), specifically refers to this abnormal transformation occurring on or within a joint, and involving loose or undermined cartilage or bone within the joint.

Exactly why OC/OCD occurs in horses is still not fully understood but many factors have been associated, including genetics and over-feeding.

OC/OCD sometimes leads to lameness, pain, joint swelling and ultimately arthritis. In other cases, it does not cause obvious problems and is found "incidentally" in x-rays taken for another reason.

The cause of OC/OCD is not well understood. There are a variety of genetic and environmental factors that contribute to it. Over-nutrition may be a significant contributing factor. Studies suggest that foals turned out in pasture have a lower incidence of this problem.

Diagnosis is usually made through veterinary exam and x-ray.

Treatment ranges from nothing to changes in management (feeding) to surgical (arthroscopic) removal of loose cartilage and poor quality bone.

my vet's role


Treatments May Include

These treatments might be used to help resolve or improve this condition.

Very Common
Less Common
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Good to poor, depending on the specific joints affected and the severity of the problem.

my role


I might observe

You might make these observations when a horse has this condition.

Very Common
Less Common
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Questions To Ask Your Vet:
  • Why did my horse end up with this condition?
  • Are my other horses at risk of developing the condition?
  • What happens if nothing is done?
  • What can I change in my breeding and management to reduce likelihood of this condition?

Genetics: Choose lines of horses that do not have a high incidence of the condition.

Management: Provide appropriate nutrition to pregnant mares and growing foals. Do not overfeed or over nourish growing foals.

Pre-purchase exams: Be on the lookout for this condition. Have a PPE performed before purchasing a horse.

further reading & resources

Related References:

Koenig TJ1, Dart AJ, McIlwraith CW, et al. Treatment of experimentally induced osteoarthritis in horses using an intravenous combination of sodium pentosan polysulfate, N-acetyl glucosamine, and sodium hyaluronan. Vet Surg. 2014: 43(5):612-22.

Author: Doug Thal DVM Dipl. ABVP