Osteoarthritis heavily impacts equine industry
Osteoarthritis, commonly known as joint disease in horses, is simply inflammation of a joint, says Dr. Erin Contino of Colorado State University, who looks at what osteoarthritis is, what causes it and how equine producers can treat the condition in their horses.
“If we take a step back and think about what osteoarthritis is, we have to understand the joint has a lot of different parts to it,” she continues.
Biology of a joint
Joint disease – which is between two bones – can result from damage to the subchondral bone, articular cartilage, which overlays the subchondral bones, a joint capsule and lining on the inside of the joint.
“The lining on the inside of the joint is called the synovial membrane, and that’s what produces most of the fluid necessary to create a healthy joint environment,” Contino explains. “When we think about joint disease, it can be an injury to any of those structures that can set of this vicious cycle.”
Contino emphasizes, “Damage to any of these structures sets off a chain that continues to damage the remaining structures.”
Causes in equine
For horse owners, osteoarthritis is most frequently caused by repetitive, cyclic, low-grade trauma.
“We don’t think of a lot of what we do as being traumatizing,” Contino says. “But if we do things over and over with enough repetitions, we see fatigue, whether we are talking about a man-made structure or not. We can only withstand so much cyclic load.”
In this way, low-grade trauma is often seen in performance horse in low-motion joints, particularly the hocks and pastern joints.
“The hocks are, across the board, where we see most osteoarthritis in horses,” she comments, noting it is also seen in the coffin joint, fetlock, carpus and stifle. “With increasing frequency, we are diagnosing osteoarthritis in the axial skeleton.”
Osteoarthritis can also result as a secondary ailment resulting from acute trauma. Infection in the joint, mechanical trauma or soft tissue injuries can also result in osteoarthritis.
Breed, conformation and use can also impact a horse’s probability of getting osteoarthritis.
Radiographs and clinical exams are used to diagnose osteoarthritis in horses, says Contino.
“When we do our physical exam, we are oftentimes palpating them for obvious things like heat,” she says. “However, unless it is severe, we don’t feel heat. Very often, we can feel joint effusion, which is simply too much fluid in the joint.”
Additionally, decreased range of motion and pain on flexion can be seen.
In a dynamic exam, as the veterinarian watches the horse move, common complaints include general tightness, loss of fluid movement or lameness, which is most common.
“I like to think of treating osteoarthritis as a multi-pronged approach when we think about having options to treat our horse systemically,” she said. “Then, we should go more focally, intra-articular, which includes medication we can put directly into the joint.”
Finally, several other treatments are available, including shockwave, bisphosphonates and physical therapy.
“One piece that is often overlooked are the different management considerations, including husbandry items, diet and exercise or farrier treatments.”
When looking at osteoarthritis, systemic treatments treat the whole body.
“Our most common system treatment is non-steroidal anti-inflammatory drugs (NSAID),” Contino says. “These are things we are very familiar with, like Bute and Banamine. Those are the workhorses of our NSAIDs.”
Equioxx, a newer NSAID, and Surpass, a topical drug that absorbs through the skin, are also available.
Beyond that, however, there are severe limits on system drug options for treating horses.
“In horses, we still really rely on some of the things we have had in our toolbox for decades,” she comments.
Similar to NSAID use in humans, Contino cautions producers there may be kidney and gastrointestinal side effects to using these drugs.
“We need to be cautious and certainly conservative with our use, particularly in geriatric horses that are more prone to kidney disease,” she says.
Another category of systemic treatments include injectable products, with three that are most common. Adequan, Legend and Pentosan are most often seen in the U.S., Contino says.
Another massive market under the umbrella of systemic treatments are nutraceuticals. The industry exceeds $1 billion annually for all companion animals, including horses.
“However, they are not regulated by the Food and Drug Administration (FDA), so they are not produced in an FDA approved lab, and they do not have to meet their label claims,” Contino explains. “This is a bit of a ‘buyer-beware’ situation. I’m not saying nutraceuticals are not useful because there are reputable companies.”
While systemic treatments can be very effective throughout the body, intra-articular treatments allows horse owners to “get the most bang for their buck.”
“If we have a horse that has osteoarthritis in only one or two joints, typically we get the best response if we can inject treatments directly into the joint,” Contino notes. “The real power house of this category are our corticosteroids.”
She continues, “Corticosteroids have gotten a bad name. There is a propensity that they could be abused, but they are very effective. These are the most potent anti-inflammatory drugs, and they are also very cost-effective.”
However, these treatments must be injected in sterile situations. At the same time, when the corticosteroid is administered, it is often given in conjunction with hyaluronic acid, a joint lubricant.
“The corticosteroid is typically the inexpensive part of treatment,” Contino notes. “Typically, hyaluronic acid is more costly.”
She summarizes, “When used judiciously, they are very cost effective and effective medication.”
This webcast was sponsored by Boehringer Ingelheim Vetmedica and TheHorse.com.
Saige Albert, managing editor of the Wyoming Livestock Roundup, can be reached at firstname.lastname@example.org.