Technical information for veterinarians
Osteochondrosis (OCD) in Horses
What is osteochondrosis (OCD)?
Osteochondrosis is a form of developmental orthopedic disease that involves a local or generalized failure of endochondral ossification affecting the epiphyseal and/or metaphyseal cartilage. Two clinical syndromes affect horses:
- osteochondrosis dessicans (OCD)
- subchondral cyst-like lesions (bone cysts)
Etiology of osteochondrosis
Endochondral ossification occurs in the bones of the extremities, the vertebral column, pelvis, and base of the skull. Bone is formed from a hyaline cartilage matrix, which becomes ossified.
Several steps are involved in normal endochondral ossification:
- First, chondrocytes mature and enlarge
- The intracellular matrix begins to thin
- The mature chondrocyte produces alkaline phosphatase. This causes the intracellular matrix to calcify
- Calcification of the matrix in turn causes the chondrocytes to die.
- Vascular penetration of the area then occurs and osteoblasts within the matrix produce bone, which matures to lamellar bone.
Osteochondrosis develops when:
- Cartilage cells that have proliferated in a normal manner, mature and differentiate abnormally.
- Failure of the cartilage matrix to calcify or failure of vascular penetration and osseous replacement causes the cartilage to thicken.
- Due to the lack of nutritional elements, necrosis develops in the deeper layers, giving rise to fissures.
- Eventually, a cartilagenous flap (OCD) develops.
Sometimes, the thickened cartilage persists without developing fissures and becomes surrounded by subchondral bone. Adjacent normal cartilage continues its endochondral ossification and the retained cartilage dies. This results in a subchondral cyst-like lesion.
Osteochondrosis frequently leads to arthritis.
Symptoms/diagnosis of osteochondrosis
The symptoms of osteochondrosis depend on the area that is affected by the condition. Stiffness, lameness and pain in the affected joint are common signs that a horse may have developed the disease. (Unlike other animals, a horse with osteochondrosis does not always experience pain.)
The horse may try to compensate for the lameness by restricting movement of the affected joint. If the leg is affected, the horse may swing its leg outward in a circular motion to avoid bending the leg. Although the condition usually affects both sides, one leg is often worse than the other. The horse may therefore take extra weight on the better leg, resulting in decreased muscle development in the other leg affected by osteochondrosis.
Risk factors for osteochondrosis in horses
Genetic influences, overweight, prolonged inactivity/intense activity and improper shoeing are all believed to contribute towards the likelihood of developing osteochondrosis.
The tendency to develop osteochondrosis is inherited, with larger, fast-growing breeds of horse being more likely to develop the condition. However, not all horses whose parents have the condition will develop it themselves.
Excess intake of calories, phosphorous and calcium is believed to play a part in the onset of osteochondrosis in susceptible horses. Slowing the rate of growth of large breeds of horses has been shown to reduce the incidence of osteochondrosis.
Osteochondrosis develops as a consequence of defective transformation of cartilage into bone. If a young horse overuses a joint affected by osteochondrosis, defective cartilage can separate from the bone to which it is attached. Separation of cartilage from bone causes pain and joint instability and initiates the development of secondary arthritis. (Many arthritic changes, such as bone spur formation, develop when the horse’s body attempts to stabilize the joint by adding “wedges” of bone.) By restricting the amount and intensity of the horse’s exercise, osteochondrosis is less likely to occur.
Improper shoeing can cause many joint and muscle problems and is a significant factor in the progression of degenerative disease. An experienced farrier will be able to ensure a horse is shoed correctly.
Treatment options for osteochondrosis
The treatment for osteochondrosis is geared towards inhibiting further breakdown of the joint cartilage and bone and decreasing the pain the horse may be experiencing. Various drug therapies and surgical treatments can ease discomfort and restore mobility.
The type of treatment depends upon several factors, such as the age of the horse, the severity of the problem and financial considerations. Management of the condition usually consists of exercise restriction, body weight management and symptomatic pain management with analgesics and anti-inflammatory drugs.
Restricting the amount and intensity of a horse’s activity has been shown to reduce the incidence of osteochondrosis. Flaps of cartilage that have not yet broken away from their underlying bone may heal back if the affected joint use is not too intense or prolonged. Horses should participate in only regular short walks until they have finished growing. This recommendation is particularly important if the horse already has osteochondrosis.
Overfeeding contributes significantly to the development of many orthopedic conditions in horses, including osteochondrosis. The horse’s total caloric intake should be reduced and vitamin/nutritional supplements reduced unless specifically indicated.
Analgesic and anti-inflammatory medications
These should only be used for the short term, when necessary to encourage movement. Commonly used analgesics and anti-inflammatories include acetaminophen and various NSAIDs.
For mild to moderate osteochondrosis in horses, acetaminophen (Tylenol®, Panadol®, Exdol®, etc.) may be prescribed to relieve pain.
NSAIDs help reduce pain and swelling of the joints and decrease stiffness. When taken at a low dose, NSAIDs reduce pain; when taken at a higher dose, NSAIDs can also reduce inflammation. NSAIDs do not prevent joint damage and when used over the long-term, may accelerate joint breakdown. Taking more than one NSAID at a time increases the possibility of severe side effects such as ulcers and bleeding. The newer sub-class of NSAIDs (used currently for companion animals), known as Cox-2 Inhibitors, includes Rimadyl® (carprofen), Metacam® (meloxicam) and Etogesic® (etodolac).
When pain and inflammation is severe, a corticosteroid, such as cortisone, may be injected directly into the affected joint/s. An injection can provide almost immediate relief for a tender, swollen and inflamed joint.
Pentosan polysulphate (Cartrophen Vet®) is an injectable drug is given at weekly intervals, usually on four separate occasions. The drug acts in many different ways, but primarily improves the environment of the joint cartilage. Painkillers are contraindicated while pentosan polysulphate is being administered.
Visco-supplementation is the process of injecting a gel-like substance into the joint. This substance lubricates the cartilage, reducing pain and improving flexibility. Visco-supplementation decreases friction within the joint, thus reducing pain and allowing greater mobility. This method of treatment requires ongoing injections as benefits are only temporary. Substances used in visco-supplementation include hyaluronic acid, or HA (Legend®, Hylartin® and Synacid®), and poly-sulfated glycosaminoglycans (PSGAGS) such as Adequan®.
If surgery is required
A number of surgical techniques are employed in the treatment of osteochondrosis. The goal of the surgical procedure is to remove any loose pieces of cartilage from the joint surface and curette (scrape) the cartilage defect to encourage the body to refill the dessicated areas. Surgery should always be considered a last resort, when all other attempts to help the condition have failed.
In some very young horses, the cartilaginous flap associated with osteochondrosis may heal on its own. It is therefore worth waiting to see if the lameness resolves itself spontaneously. Surgery should not be delayed too long, however, if the horse continues to exhibit lameness.
Natural options for horses with osteochondrosis (OCD)
Recovery®EQ with Nutricol®, is an elite proprietary performance and wellness supplement for horses that enhances quality of life.Recovery®EQ improves healing by increasing circulation of nutrients to affected cells and extracellular structures, halting tissue damage and decreasing inflammation. It may be used on its own or in combination with prescribed medications. Ask your veterinarian how Recovery®EQ can help your horse.
Review in the prestigious Horse Journal in October and December 2003
Recovery®EQrated as “Best Performer Overall” as a pain-relieving supplement for joint pain, back pain and tendonitis – comparison of natural joint care supplements.
Review in the prestigious Horse Journal inJune 2006:
“You get what you pay for” – Horse Journal quote about Recovery®EQ used as a performance enhancing supplement – comparison of natural performance enhancing supplements
For more information on helping your horse stay healthy, please see Tips for a Healthier Horse