Joint Maintenance (Book Excerpt)

Editor's Note: This is a short excerpt from Chapter 8 (Musculoskeletal Maintenance) of Understanding Equine Preventive Medicine, written by Bradford G. Bentz, VMD, MS. The book is available from

Equine athletes are really no different than human athletes in regard to the effects of aging, exercise, and other use on the joints. Because this is the case, if a horse is used for regular performance, competition, or other exercise activity, one should see changes over a period of time relating to the joints and skeletal system. Indeed, even aging itself can lead to deterioration in such structures. It is, therefore, important that an owner and the trainer understand that no individual horse can or should be expected to compete at the same level throughout its entire life and that gradual progression of degenerative joint disease is normal and expected. However, today we are armed with a number of potentially useful and some highly proven therapies that can be used to prolong both the length of time the horse is able to compete at its highest potential level and the amount of time that the horse is able to perform the particular activity with comfort and success.

There are a number of modes of therapy that can help maintain joint health and reduce pain associated with joint disease. Such therapies may include oral medications, oral joint supplements, intramuscular medications, intravenous medications, and intra-articular medications (medications that are placed directly into the joint). Other therapies include magnetic therapy, acupuncture, topically administered medications, shock-wave therapy, and more.

Intravenously (IV) and Intramuscularly (IM) Administered Joint Therapies
As is the case with oral joint supplements, the availability and use of IV and IM administered joint medications have expanded significantly in the past several years. Such therapies often include hyaluronic acid (HA) preparations (e.g., Legend and others) and polysulfated glycosaminoglycans (PSGAGs) (e.g., Adequan IM). Hyaluronic acid preparations can be administered intravenously as well as directly into the joint. In the joint, HA performs several functions, such as increasing the viscosity of joint fluid, lubricating the joint membrane and joint cartilage, and other potentially significant functions. Administering HA to a joint is believed to increase the viscosity of normal joint fluid and counter inflammation. The effects of HA in a joint are maximized by direct injection; however, there is some evidence that intravenous administration of HA can effectively manage osteoarthritis (degenerative joint disease).
PSGAG preparations are most often administered into the muscle, but preparations for direct joint injection are also frequently used. PSGAGs incorporate into the complex molecule that constitutes part of the joint cartilage matrix, decrease the activity of enzymes that cause degradation of joint cartilage, and increase the production of HA and other beneficial molecules in the joint.

Though these therapies tend to be more expensive than oral joint supplements, evidence shows they, too, support and maintain healthy joint cartilage. How expensive the medications are depends on how often they are used. As in the case of oral supplementation for joints, use of injectable joint therapies might be improved with regular and prolonged use. These medications do not cure degenerative joint disease but may aid in slowing disease progression and in maintaining normal joint cartilage. They are best used to help prevent and manage osteoarthritis (degenerative joint disease).

Intra-Articular Therapies (Medications Administered Into the Joint)
With years of performance, or when there are underlying and perhaps chronic joint problems, medications administered orally or by IM and/or IV injection may become inadequate to provide prolonged relief of joint pain. This leads to reduction in performance for that animal. When this occurs, a specific lameness examination is advisable to identify the affected joint(s). This is typically done by your veterinarian with the use of flexion tests, nerve blocks, joint blocks, radiography, ultrasound examination, and/or other diagnostic imaging techniques. If joint disease is diagnosed, intra-articular therapies (joint injections) should be considered.

A number of people strongly object to joint injections. Their staunch opposition may have stemmed from the barrage of research specifically on the use of steroids in joints that emerged in the late 1960s and '70s. This research emphasized the potential for adverse effects of corticosteroids on joint cartilage. The incidence of these adverse effects is probably increased by frequent and repetitive use of steroids in a joint with significant underlying problems and continued athletic exercise. A steroid's potency and individual characteristics may impact the likelihood of negative effects on cartilage when used frequently and when athletic use is continued at the same level.

Despite the obvious stigma left from this information regarding steroidal joint injections, veterinary administration of this therapy can greatly reduce potential for negative effects. One major consideration is that not all joint therapies are steroids. In fact, hyaluronic acid (HA) and polysulfated glycosaminoglycans (PSGAGs) have also been regularly and safely administered into joints. Administration of HA and PSGAGs into a joint helps control inflammation. Secondly, your veterinarian will diagnose any joint problem that may exist and determine the best way to manage the condition. For instance, a bone chip in an ankle might require surgery followed by regular maintenance therapy with intramuscular administration of PSGAGs for several weeks after surgery and at regular intervals thereafter. For degenerative joint disease, your veterinarian may be able to control pain and inflammation with intermittent anti-inflammatory medications and/or oral joint supplements for a prolonged time. Progression of the disease might require more intensive therapy with hyaluronic acid and/or PSGAGs. Depending on the progression and the costs of non-articular therapies, joint injections may be the most practical and effective way to control the problem.

The type of steroid should be selected with care and is best left to your veterinarian. Frequently, steroids are mixed with hyaluronic acid or steroid types are mixed with one another. For instance, a "short-acting" steroid may be mixed with a "long-acting" steroid. Commonly affected joints that can be relatively easily injected include the coffin joints, fetlock joints, carpal joints (knee), pastern joint, stifle joints, and hock joints. A single administration of a steroid into a joint is commonly effective for many months and occasionally much longer. It may be most practical and most effective to consider this therapy over others. The longevity of the clinical effect will be important to monitor along with re-evaluation of the "soundness" and X-rays to follow the disease�s progression. It is probably more fair and humane to the performance horse to administer intra-articular steroids than to force the animal to perform in pain continually with poor results. Many horses can continue for years using judiciously administered steroidal joint injections. However, there is a point at which the frequency of steroid use in a joint becomes unreasonable and destructive. In such cases, with continued progression of joint disease, eventual retirement of the animal from competition may become necessary, rather than increasing the number of joint injections to a more potentially adverse frequency. Your veterinarian will help you make this decision.

Overall, joint injections are safe to the horse when administered by a conscientious practicing veterinarian. Their overall negative effects on joint cartilage are insignificant when they are properly administered at safe intervals. Their anti-inflammatory effect on the joint may persist for many months or longer depending on the underlying stage of joint disease. The horse will be able to perform comfortably and to its ability with judicious use of joint therapies. It may be unfair and inhumane to continue to expect your horse to perform comfortably and successfully without therapy when there is degenerative joint disease. For this reason, if one insists on the exclusion of joint injection for his/her horse, it becomes necessary to manage the condition using the available oral IM and IV medications. These therapies are less likely to provide significant relief from degenerative joint disease, as they are best used as "preventive" medications and not as "therapeutic" medications. Without specific joint injection therapy, persistent pain necessitates the horse's retirement and purchase of another if competition is still a goal of the rider.

About the Author

Bradford G. Bentz, VMD, MS, Dipl. ACVIM, ABVP (equine)

Brad Bentz, VMD, Dipl. ACVIM, ABVP, ACVECC, owns Bluegrass Equine Performance and Internal Medicine in Lexington, Ky., where he specializes in advanced internal medicine and critical care focused on helping equine patients recuperate at home. He’s authored numerous books, articles, and papers about horse health and currently serves as commission veterinarian for the Kentucky State Racing Commission.

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