As horse owners, you have been bombarded with numerous articles and advertisements that deal with the prevention and treatment of joint disease in horses. Although joint therapy has been primarily targeted at Thoroughbred and Quarter horses, there are even miniature horses that deal with the same sorts of problems. Breeding stallions and driving horses are especially prone to joint soreness.
Traumatic joint disease in horses includes synovitis (inflammation of the fluid-producing membrane), capsulitis (inflammation of the fibrous joint capsule), articular cartilage and bone fragmentation, ligamentous tearing, and eventually osteoarthritis. In many cases, the disease process primarily involves soft tissue overuse and microtrauma to the bone surfaces, and therefore can be challenging to diagnose without diagnostic anesthesia. In addition to localizing pain to a certain joint with aide of diagnostic anesthesia, radiographs, ultrasound, computed tomography, magnetic resonance imaging (MRI) techniques and diagnostic arthroscopy have all be used to confirm causes of joint lameness.
Trusting your veterinarian to decide when joint injections may be beneficial for your horse is prudent. There is no gold standard for the diagnoses of preliminary joint disease in the horse as radiographic changes are usually indicative of irreparable harm.
Aggressive treatment in joint disease is indicated to decrease immediately soft tissue swelling and inflammation as well as to postpone the onset of permanent osteoarthritic changes. There is inherent difficulty in identifying joint pathology by any other means than subjective examination and lameness or shortness of stride reports from trainers. The goal of any systemic or intraarticular (medications put directly into the joint) therapy is to stop problems before they occur rather than wait for abnormal radiographs and then start aggressive therapy.
Inflammatory and degradative enzymes that destroy normal joint environments can be altered by use of hyaluronic acid (HA) and corticosteroids injected into the joint. The combination of the two has been scientifically proven to have a more thorough and lasting effect than HA alone or corticosteroids alone. Select corticosteroids have been evaluated in the equine research model proving their efficacy and have shown certain corticosteroids to be protective to the joint environment.
Medications introduced into joints by human physicians that specialize in sports medicine are becoming more commonplace. Previous generalizations and perpetuation of myths about damage to joint environments caused by corticosteroids are primarily unfounded.
Typically, when there is mild soreness (joint capsulitis or synovitis) in a joint, and joint therapy is instituted 2 to 3 times per year, the environment inside the joint becomes more hospitable to cartilage, not destructive. Damage may occur from excess corticosteroid injections or when there is cartilage fragmentation and bone alterations in a joint, usually associated with lameness. This is why your veterinarian may require a radiograph before instituting joint therapy.
The metabolism of the equine joint is different than in other species. They are not afflicted with Charcot-Like arthropathy that occurs in humans with the development of arthritis from corticosteroid injections. It has been proven that corticosteroids and HA together allows the natural synovial lining of a joint to make a more favorable environment.
Intraarticular Hyaluronic Acid (HA)
Probably the most commonly used HA products are Hylartin-V, HyVisc, Legend or Hyalovet. All of these products are labeled for intraarticular use insuring purity and consistency with each individual manufacturer. HA is normally synthesized by the synovial membrane and is responsible for the boundary lubrication of articular cartilage.
This class of drug gained much fame, as it is commonly used in racehorses with arthritis and has been blamed for many injuries post-injection. Research has proven that when used correctly, these medications are beneficial in the pathogenesis of joint disease. As we mentioned earlier, enzymes that are produced by diseased or inflamed joints are very destructive to normal cartilage.
Joints that are inflamed must be treated with anti-inflammatory medication, as well as HA in some instances, to allow them to return to their normal environment. Intraarticular corticosteroids allow the joint to start producing lubricating HA as inflamed joint tissues WILL NOT produce viscous or thick, lubricating HA. It was once said that a human on corticosteroids can walk to the autopsy room but now most orthopedic surgeons use these products in the most famous athletes in the world. Horses are, by far, much harder on their joints than any human athlete. It only makes sense.
Substantiation for a direct link between corticosteroid administration and arthritis has persistently been unable to prove by dozens of investigators. Most of the problems associated are attributed to poor technique (infection), poor selection of corticosteroid products, or irreversible damage resulting in a non-functional joint.
Do your own research. Take responsibility for the care of your athletic horse. We, as humans, have a lot to offer the athletic equine with therapy and medication that has been borrowed from the human medicine field, which has been designed specifically for use on the horse.
Dr. Darin Peterson, DVM, was born and raised on a horse and cattle ranch in Rosholt, S.D., and received his B.S. in Animal Science from SDSU. He concentrates most of his work time with large animals. He can be reached at 701-347-5496 or email@example.com.