OCD – Osteochondritis Dissecans

Osteochondritis dissecans (OCD) is a relatively common developmental disease that affects the cartilage and bone in the joints of horses. OCD can occur in all breeds, especially in big size horses, and can show clinical signs in up to 30% of them. Cartilage in joints with OCD doesn’t grow normally causing it and the bone underneath to become irregular in thickness and weaker until they develop into flaps that can either remain partially attached to the bone or break off and float around in the joint. These loose flaps cause inflammation in the joint and predispose it to arthritis.

What causes OCDs?

OCD is a multifactorial disease that can be caused by:

  • Rapid growth
  • Diets very high in energy or have an imbalance in trace minerals
  • Genetics
  • Hormonal imbalances
  • Trauma

How do you spot it?

The most common sign is swelling in the joint of a young horse between 4 months and 2 years of age but may not occur until they are brought into work. The grade of lameness varies with location and severity of the OCD. OCDs can occur in all joints but they occur most frequently in the hock, stifle and fetlock.

How do we diagnose it?

The vet will need to do a physical examination with lameness workup and radiographs. OCD is often bilateral and the vet would suggest taking radiographs of the opposite joint, even if there is little or no swelling in that joint. Sometimes older horses are diagnosed with OCD incidentally without apparent clinical signs. X-rays only show bone clearly and not cartilage so sometimes it is necessary to enter the joint surgically (through an arthroscopy) to assess the degree of damage under general anaesthesia.

How do you treat it?

The best treatment is surgical removal of the abnormal bone and cartilage is through arthroscopy under general anaesthesia. Arthroscopy is performed by making two or more small incisions into the joint through which a small camera called an arthroscope and other specially designed instruments are placed. Aftercare recommendations depends on the location and severity of the OCD but they always require a period of box rest followed by progressive exercise with full return to training in several months.

What’s the prognosis?

Prognosis for athletic function is good to excellent for most OCDs that are treated surgically but depends on the location and the severity of the OCD. In general, if the OCD lesion is not removed the prognosis for future soundness will be decreased.