Last program I talked about the causes of bone growth problems in horses and one of the most common is osteochondritis dessicans, or OCD. OCD commonly occurs in foals in the stifles, hocks, and fetlocks. It is caused by a flap of cartilage that breaks off from the joint surface, which can lead to pain and lameness. Sixty percent of the cases diagnosed are in horses less than one year of age, and some cases have mild lameness with only swelling of the affected joint.
Diagnosing OCD can be difficult because although many cases can be diagnosed with x-rays, the OCD lesions do not always show up on x-ray. Also, the disease commonly occurs in both joints so if it is in one leg in a certain joint, the other leg should always be checked. Dr. Wayne McIlwraith from Colorado State indicates that diagnosing some of these cases requires placing a scope in the joint and looking at the joint surface. Treatment of most OCD lesions requires surgery that can also be performed with a scope; this prevents the need for a large incision as the surgery can be performed through two little holes. Some horses with small lesions may respond to rest and may not require surgery, but you always run the risk of arthritis developing later in these joints.
Another related problem in young horses is the subchondral bone cyst. A sac-like cavity forms in the bone just below the joint surface and is usually noted as a cause of lameness in horses less than 3 years old. Treatment of these cysts is controversial as some believe surgery is required while others have had success injecting the cysts with cortisone and other medications.