As horse owners, we are constantly bombarded with articles and advertisements regarding the prevention and treatment of joint disease in horses. While joint therapy has traditionally been focused on Thoroughbred and Quarter horses, even miniature horses can experience similar issues. Breeding stallions and driving horses, in particular, are prone to joint soreness.
Traumatic joint disease in horses encompasses various conditions such as synovitis (inflammation of the fluid-producing membrane), capsulitis (inflammation of the fibrous joint capsule), articular cartilage and bone fragmentation, ligament tearing, and eventually osteoarthritis. Diagnosing these conditions can be challenging without diagnostic anesthesia, as the disease process often involves soft tissue overuse and microtrauma to the bone surfaces. In addition to subjective lameness evaluation, diagnostic techniques such as radiographs, ultrasound, computed tomography, magnetic resonance imaging (MRI), and arthroscopy are employed to confirm the causes of joint lameness.
Trusting your veterinarian to determine when joint injections may be beneficial for your horse is a wise decision. There is no definitive “gold standard” for diagnosing preliminary joint disease in horses, as radiographic changes usually indicate irreversible damage.
Aggressive treatment in joint disease aims to reduce soft tissue swelling and inflammation immediately, as well as delay the onset of permanent osteoarthritic changes. However, identifying joint pathology through means other than subjective examination and lameness reports can be challenging. The goal of systemic or intraarticular therapy is to proactively address potential problems rather than waiting for abnormal radiographs before starting aggressive treatment.
Inflammatory and degradative enzymes that damage normal joint environments can be modulated using hyaluronic acid (HA) and corticosteroids administered directly into the joint. Scientific evidence supports the combination of HA and corticosteroids as having a more comprehensive and long-lasting effect compared to either HA or corticosteroids alone. Select corticosteroids have been evaluated in equine research models, demonstrating their efficacy and protective properties for the joint environment. However, it is important to note that not all corticosteroids are equal, and some can be detrimental to joint health.
Medications used in joint therapy in human sports medicine are increasingly being applied in equine medicine as well. Previous generalizations and myths regarding corticosteroid-induced damage to joint environments are largely unfounded. Typically, when mild joint soreness (capsulitis or synovitis) is present, and joint therapy is administered 2 to 3 times per year, the joint environment becomes more favorable to cartilage rather than destructive. However, excessive corticosteroid injections or injections into joints with cartilage fragmentation and bone alterations can lead to damage. This is why your veterinarian may require radiographs before initiating joint therapy.
The metabolism of equine joints differs from other species, and horses are not susceptible to “Charcot-Like” arthropathy, a condition observed in humans receiving corticosteroid injections. Studies have demonstrated that the combination of corticosteroids and HA allows the natural synovial lining of a joint to create a more favorable environment.
Intraarticular Hyaluronic Acid (HA)
Commonly used HA products include Hylartin-V, HyVisc, Legend, or Hyalovet. These products are labeled for intraarticular use to ensure purity and consistency. While not labeled for joint therapy, MAP-5, a type of hyaluronic acid used in sperm extenders, has been employed in joint therapy. HA is naturally synthesized by the synovial membrane and is responsible for the boundary lubrication of articular cartilage. Experimental evidence, combined with reports from equine sports medicine practitioners, suggests that using the highest molecular weight (thickness) of HA provides the most benefit.
Polysulfated Glycosaminoglycans (PSGAGs)
Adequan is the most common example of PSGAGs. This product is administered via intramuscular injection, but it can also be used intraarticularly under strict aseptic conditions and in combination with antibiotics. PSGAGs primarily serve as building blocks for successful cartilage repair. They are usually employed when cartilage damage is already present rather than in cases of acute joint inflammation. Arteparon is the human equivalent of Adequan, and the chemical structure of both products is identical. Chondroitin sulfate, harvested from bovine lung and trachea, is the most commonly used GAG in these products.
Oral Joint Supplementation
Many oral supplements contain chondroitin sulfate, glucosamine, MSM, and various other GAGs. It’s important to note that these supplements are not regulated by the Federal Drug Administration.
Glucosamine is a sugar compound naturally produced in the horse’s body. It is incorporated into various molecules, including joint cartilage. However, it is not essential for cartilage synthesis, as the body uses glucose to build cartilage. Glucosamine supplements for horses are mainly derived from the shells of crustaceans. Although test-tube studies have shown biological activity and beneficial effects on cartilage cells, the concentrations used in these studies are much higher than what can be achieved through feeding. The limited bioavailability of glucosamine in horses raises questions about its effectiveness when fed as a supplement.
Chondroitin sulfate (CS) is a sugar molecule found in cartilage, bone, tendons, and ligaments. The CS fed to horses comes from animal sources, and absorption can vary depending on the product’s origin. There is still uncertainty about the extent of absorption, and studies have not shown increased blood levels after ingestion. The poor absorption of CS also raises doubts about its relevance in test-tube studies. As a result, the specific benefits of CS supplementation in living horses remain uncertain, and different CS compounds can have varying effects.
Combination of Chondroitin Sulfate and Glucosamine
While there is conflicting evidence from various species, three clinical trials specifically conducted in horses have reported beneficial effects of the combination of glucosamine hydrochloride and CS on symptoms of joint disease. These studies, funded by the industry, suggest some symptomatic relief in lameness.
This class of drugs has gained both fame and infamy, as they are commonly used in racehorses with arthritis and have been blamed for post-injection injuries. However, research has consistently shown that when used correctly, corticosteroids are beneficial in treating joint disease. Enzymes produced by inflamed or diseased joints can be very destructive to normal cartilage. Inflamed joints require anti-inflammatory medication and, in some cases, HA to restore a normal joint environment. Intraarticular corticosteroids help stimulate the production of lubricating HA by the joint since inflamed joint tissues do not naturally produce thick, lubricating HA. The belief that corticosteroids are detrimental to joint health is outdated, and orthopedic surgeons now commonly use them in the treatment of elite human athletes. Horses put much greater stress on their joints than any human athlete, so the use of corticosteroids in equine joint therapy makes logical sense.
Nonsteroidal Medication (NSAIDs)
Phenylbutazone (Bute), flunixin meglumine (Banamine), and ketoprofen (Ketofen) are commonly used NSAIDs in horses, while aspirin and ibuprofen are commonly used NSAIDs in humans. These medications effectively alleviate discomfort and are usually the first line of therapy for minor musculoskeletal pain. They work by modulating the inflammatory cascade and downregulating mediators produced during the inflammatory process. However, it’s important to note that the most common and severe side effects of these medications include gastrointestinal ulceration and reduced kidney perfusion. The development of ulcers is becoming increasingly recognized as a common occurrence in horses of all breeds due to stress, and NSAIDs can contribute to this process.
In conclusion, the intent of these articles is to demystify veterinary medicine and encourage an informed approach to horse care. Your veterinarian will appreciate thoughtful questions, and conducting your own research is encouraged. Taking responsibility for the well-being of your athletic horse is crucial. We, as humans, have much to offer the athletic equine with therapies and medications borrowed from the field of human medicine, specifically designed for use on horses. By working closely with your veterinarian and understanding the various joint medications available, you can make informed decisions about the best course of treatment for your horse’s joint health. Remember, the ultimate goal is to ensure the longevity and well-being of our equine companions.
By Staff writer