Daniel J. Burba, DVM, Diplomate ACVS, LSU-SVM Equine Health Studies Program, Baton Rouge, LA
Neely L. Heidorn, PhD, LSU AgCenter
Degenerative joint disease (DJD, osteoarthritis) is very common in horses. Resolution of lameness is the main reason many owners and trainers seek veterinary care. Ideally, treatment of joint disease should serve to arrest or slow its progression. There is a wide array of joint supplements currently available. Some are valid and substantiated by research but others are not. Joint supplements can be categorized according to their mode of action. In a broad sense they can be classified as either pharmaceuticals either nutraceuticals.
Among the medications available for the treatment of equine joint disease, corticosteroids are the most potent anti-inflammatory medications. Intra-articular corticosteroids (IAC’s) reduce synovial membrane inflammation, the cause of joint effusion, pain, and local heat. They also suppress pro-inflammatory enzymes, which are considered the leading cause of joint pain and inflammation. Very little of the corticosteroid is absorbed into the cartilage; major local inflammatory effect is exerted in the synovial membrane. The commonly used corticosteroids used IA are betamethasone, methylprednisolone, and triamcinolone.
One of the detriments to the use of IAC’s is cartilage degradation with repeated use. There has been long-standing controversy surrounding the use of IAC’s because of the concern that overuse of a pain-free joint could result in accelerated cartilage degeneration. This has been compounded by studies showing negative effects of corticosteroids on chondrocyte (the cells that maintain the cartilage in the joint) metabolism. However, more recent studies have shown that these changes are reversible. Although IAC’s potentially aggravate existing cartilaginous lesions in horses in intense training, this event is less prevalent than reported. So the bottom line, certain IAC’s are not as bad for the joint as previously thought.
Hyaluronan (Hyaluronic Acid, Sodium Hyaluronate
Hyaluronan (HA) is a nonsulfated glycosaminoglycan (GAG) in a highly hydrated flexible coil. HA appears to primarily benefit the synovial membrane which lines the joint cavity. HA serves as the principal lubricant of the soft tissues in the joint. Some investigators and practitioners feel that the therapeutic benefits of HA is dependent on the MW (thickness) of the HA. Higher MW solutions exhibit better elasticity and storage modulus, providing better resistance to physical shear; basically more resistance to physical pressure. Higher MW HA (> 500,000 daltons) has a more effect in stimulating HA synthesis in the joint.
The primary indication for HA is synovitis (inflammation of the synovial membrane). It is routinely being administered intra-operatively post-arthroscopic surgery as well as post-joint infection. HA has limited efficacy for treating severe DJD. Some practitioners combine HA with corticosteroids. Ha is commonly administered intra-articularly (IA) or intravenously (IV).
Polysulfated Glycosaminoglycan (PSGAG)
PSGAG is a sulfated GAG. PSGAG is considered chondroprotective because of its ability to inhibit proteoglycan and collagen degrading enzyme (biochemical) activity on the articular cartilage. It has this ability by binding to the articular cartilage surface.
Arthritis is the primary indication for use of PSGAG. It is recommended to administer 1 vial weekly IM for 8 weeks. It is of no value to administer 1 vial monthly for maintenance. With only monthly treatment, PSGAG does not maintain high enough concentrations to be of value.
There are several products available as nutritional supplements for the treatment of osteoarthritis. The word was coined from combining nutrition and pharmaceutical. Nutraceuticals are remarkably successful commercially and there are numerous reports evaluating their efficacy. However, there is no consensus on their efficacy and, interestingly, no real understanding of a possible mechanism for their proposed efficacy. Nutraceuticals are not currently subjected to the same regulatory guidelines as pharmaceuticals. Nutraceuticals are marketed by manufacturers under the pretext of dietary supplements, and as such, they are excluded from the Food and Drug Administration (FDA) regulatory process. The FDA defines a dietary supplement as a product that is intended to supplement the diet and contains at least one or more of the following ingredients: a vitamin; a mineral; a herb or other botanical; an amino acid; a dietary substance for use to supplement the diet by increasing total dietary intake; or a concentrate, metabolite, constituent, extract, or combination of any of the previously mentioned ingredients.
The most popular nutraceuticals currently on the market are glucosamine sulfate and chondroitin sulfate. These are for the most part formulated together as a ‘joint supplement’. Glucosamine sulfate and chondroitin sulfate are essential to the cartilage matrix (make-up) so it would be logical that replacement of the building blocks would be beneficial. However, the oral bioavailability of glucosamine and chondroitin in the horse is often questioned because it is low in humans and other species when determined by intestinal absorption of radiolabeled compounds. There are a wide variety of products available with varying concentrations of glucosamine sulfate and chondroitin sulfate. This author recommends the use a product that contains both compounds.
Other products that are currently gaining attention for treatment of arthritis in horses include soybean plus avocado, and omega-3 fatty acids. Methylsulfonylmethane (MSM), a derivative of DMSO, has also been available for several years but its use has not been favorable in this author’s experience. Interleukin-1 Receptor Antagonist Protein (IRAP)
Interleukin-1 (IL-1) is a major player in the inflammatory cascade causing synovitis and joint pain. IRAP (Interleukin-1 Receptor Antagonist Protein) is an anti-inflammatory protein that blocks the destructive effects of inflammatory mediator (IL-1) within an inflamed joint. It is hypothesized that it binds to the IL-1 receptors (major cause of joint inflammation) in the joint thus preventing the interaction of IL-1 with the receptor. By blocking this interaction, pain and inflammation in the joint is reduced.
IRAP is obtained for injection into a joint by harvesting the horse’s own blood. A special kit (Orthokine , Arthrex VetSystems, Rochester, MN) contains a 60 ml syringe with glass beads coated with chromium sulfate that stimulate WBC production of the antagonist protein. A jugular vein is aseptically prepared and the 60 ml syringe is filled with blood. The syringe containing the glass beads is then incubated at 37 0C for 24 hours. The syringe is then centrifuged to separate the IRAP rich serum from the blood. The serum is then harvested in 4 ml aliquots in a syringe and frozen until use. A 4 ml dose is injected into the joint weekly for 3 to 4 injections. It is most beneficial for synovitis. Stem cell Therapy
In a nut shell
Stem cell therapy continues to
dominate the medical news. Researchers are working to refine the use of stem cells, including joint cartilage regeneration. Stem cell therapy for osteoarthritis in horses is still in the works. It appears to have promising result, but more research is needed as to its beneficial usefulness in joint disease.
To bring it all together, this author recommends the following for acute joint pain and inflammation in the equine athlete – Judicious use of systemic nonsteroidal anti-inflammatory drugs, rest, cold therapy (ice and cold) water and support. If the pain and inflammation persists then, IAC’s and IRAP are recommended. To maintain joint health, PSGAG (Adequan) and Nutraceuticals should be considered. If osteoarthritis or advanced joint disease is present, the stem cell therapy is the last option. It’s a ‘given’ that joint problems are going to develop in the equine athlete. Proper treatment and rest/control exercise when it develops, is the key to prolonging the athletic life of a horse.
Medical therapy for joint disease in horses continues to expand. Existing and new therapies for joint disease are on the horizon which hopefully will provide further options for treatment for one of equine industries most debilitating diseases.
If you would like to schedule a consultation with a veterinarian about joint therapies please contact:
Equine Health Studies Program
School of Veterinary Medicine
Louisiana State University
Baton Rouge, LA 70803