|First Posted: Sept 20, 2008|
Sep 12, 2013
Developmental Orthopedic Disease (DOD), Osteochondrosis (OC), Osteochondritis Dessicans (OCD), Subchondral Bone Cysts (SBC) in Horses
by Debora Johnson
One of our dear friends just got the diagnosis of OC on her 4 year old gelding. A level one lameness and tilting of the head were the symptoms. These symptoms became noticeable when the 4 year old began his training. He has had the very best of care. His food intake was monitored, he had regular vet care, he is under 15 hands, is a light breed, etc. There were no apparent reasons to suspect OC. Because of this I have decided to research and write this article. Note Update: It turns out that the diagnosis was incorrect. The horse has tested positive for Lyme Disease. The gelding has been treated but the problems still exist. Our farrier, who works wonders, has tried a number of different approaches, but again, he is baffled. He said that the problem is not in the feet or legs. There seems to be other problems, as well, however the vets have been unable to determine the root cause. The horse's prognosis is questionable. He has been this way for several years. We are all hoping that the gelding will eventually go sound, but it does not look good.
Equine Osteochondrosis Terminology Revamped
So--What is DOD? DOD and OCD have to do with bone abnormalities of young, growing horses. It usually manifests in symptoms in young horses between the ages of 3 or 4 years of age and will reach a height of 15+ hands. Blood tests can be done on young horses to determine how prone they might be to DOD. That is something to think about in a pre-purchase vet check--especially on a young, expensive horse. As your horse grows, the soft cartilage at the ends of his long bones matures. It changes and becomes hard. With OCD the cartilage does not become hard. It breaks down. The joint erodes from lack of cartilage on the joint surface. There is an abundance of fluid in the joint. Bone cysts form and lameness and pain may develop. Finally bone grates on bone possibly causing more pain and further deterioration. No horse owner wants to hear any of these words uttered by a vet. These are degenerative type diseases that cause many problems: Endochondral ossification of the extremities, the vertebral column, pelvis, and base of the skull. They all involve degeneration or necrosis. Necrosis is the name given to unnatural death of cells and living tissue. The involvement is with the epiphysis. The epiphysis is the name for a rounded end of a long bone. Cartilage is also affected. Re-ossification (Ossification is the process of bone formation) may follow and can cause lameness and other problems. In a way it is like osteoarthritis in people.If you have ever hurt a leg or an arm enough to feel pain--you know that you try to compensate by using your other arm or leg. You guard the hurt body part. Your horse may try to do the same thing. He may favor the affected joint. For example, if the horse's leg is affected, he may alter his way of going by swinging his leg outward in a circular motion to avoid bending the leg. The condition usually affects both sides. One side is usually more affected than the other. Your horse may compensate by transferring more weight to his better side. This may reduce his pain, but it might also result uneven muscle development.
Below I will define the terms used and then breakdown symptoms, causes, and treatments.
Developmental Orthopedic Disease in horses (DOD) Merck Vet Manual
"Developmental orthopedic diseases of horses constitute an important group of conditions that includes osteochondrosis, physeal dysplasia, acquired angular limb deformities, flexion deformities, and cuboidal bone malformations."
"Osteochondrosis (see also Osteochondrosis) is one of the most important and prevalent developmental orthopedic diseases of horses. Although its specific etiology is not known, it is considered to arise from a focal disturbance in endochondral ossification. The term osteochondrosis is currently used to describe the clinical manifestation of the disorder; however, the term dyschondroplasia is preferred when referring to early lesions because primary lesions are seen in cartilage." Osteochondritis Dessicans (OCD)
Osteochondritis dissecans OCD
"Osteochondritis dissecans (OCD) or osteochondrosis is a failure of the bone underlying the smooth articular cartilage inside the joints, i.e. the subchondral bone, to form properly from the skeleton's cartilage template. This weakness results in cracking and fissure formation in the articular cartilage, when the foal, yearling or young horse takes weight on its joints during exercise. Flaps and fragments of cartilage consequently form within the joint, some of which are transformed from cartilage into bone and are termed 'joint mice.' Chemicals that cause joint inflammation (synovitis) are released during the development of the flaps and fragments, or as a consequence of exercise on the abnormal surfaces. The affected joints may become visibly enlarged and distended with fluid and the horse may become lame, but there is no doubt that many cases never show symptoms of abnormality, are never recognized and resolve in time of their own accord." (I added the bolding)
Subchondral Bone Cysts (SBC)
"The term chondral is an adjective that means of cartilage. A Subchondral bone cyst is one that happens near a joint and is beneath the cartilage around a joint. They may result from pressure or stress on articular cartilage and subchondral bone, leading to synovial fluid intrusion into the bone or bone contusion. These are commonly associated with Osteoarthritis or bone injury." by Rusty Ford
(OCD) Osteochondrititis Dessicans Syndrome
Diagnosis and Treatment Options
Always, always check with your vet before embarking on any of these suggestions.