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:
Diets very high in energy or have an imbalance in trace minerals
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.
Using selection to beat OCD
An article from the KFPS 29/04/2019
Osteochondrosis is a disorder in the development of cartilage. It starts at a very young age, somewhere between one to eight months old. It is a dynamic process and many foals heal naturally because the loose pieces of cartilage are absorbed and the OCD disappears. If not, then the loose pieces may ossify and cause problems in the joint (OCD) later in life.
Often, it is not visible from the outside that a horse has OCD, it can only be diagnosed by a veterinarian after taking X-rays. When a horse is lame because of OCD then the affliction in the joint is serious. OCD is a very common problem, about 30% of horses older than two are diagnosed. Results differ per breed but due to a lack of research not all studbooks have available data on OCD. OCD is far more common in larger equine breeds like the KWPN and KFPS than in pony breeds. Horses with a fast growth rate are more at risk of developing OCD
The question the KFPS Breeding Council is faced with right now is 'How can OCD be prevented in Friesian horses?' Waling Haijtema, veterinarian and member of the KFPS Breeding Council: ‘The Breeding Council is looking into the possibility to do progeny testing on Friesian horses just for OCD in the hock. This is the most common occurrence and has a high correlation with OCD in the knee joint. Moreover, OCD in the hock has the highest degree of heredity. If we restrict ourselves to testing of OCD just in the hock then four X-rays will suffice. It is up to the breeders to decide if this is adequate or whether they think more X-rays of their horse should be taken.’ Haijtema points out that doing nothing is not an option: ‘We have to get on top of OCD by using better selection methods.’