Horse Side Vet Guide ®

Equine Health Resource

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.


  • 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.

    Author: Doug Thal DVM Dipl. ABVP


    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.


    We're not around right now. But you can send us an email and we'll get back to you, asap.