Osteoarthritis: Not Just An Old Horse Disease.
By: Stacey Oke, MSc, DVM
Studies show 60% of all equine lameness issues are related to osteoarthritis (OA). While it is incurable, there are treatments available and research is ongoing. More than 60% of equine lameness is attributable to OA, and it is widely accepted that OA can affect any horse at any age.
Once thought to affect only older animals, Osteoarthritis (OA) will attack younger horses as well. The causes are many and varied, but in a young horse, it is usually trauma related.
There is no need to start panicking about OA the day your foal’s feet hit the ground, but its impact should be considered following every footfall thereafter.
When a horse owner says, “My horse has arthritis,” the first image that pops into our heads is an older, wizened, slightly swaybacked, retired horse standing alone in a field slowly plodding along, while his younger counterparts gallop happily past.
“This is simply not an accurate picture of a typical horse with OA,” laughs C. Wayne McIlwraith, BVSc, PhD, FRCVS, DSc, Dr. med vet (hc), Dipl. ACVS, Barbara Cox Anthony University Chair and Director of the Orthopaedic Research Center at Colorado State University (CSU).
In fact, the available data show that it is widely accepted that OA can affect any horse at any age. However, we have no firm numbers to show exactly which young horses get the disease.
Because there is no cure, the management and prevention of OA continues to be a hot topic for equine practitioners and researchers. Recently, McIlwraith presented an update on OA for his colleagues at the 11th Congress of the World Equine Veterinary Association (WEVA), held in Guarujá, Sao Paulo, Brazil. This article communicates McIlwraith’s key points presented at WEVA and relays the most recent research on various treatment modalities to keep young horses with OA functioning as fully as possible.
The Impact of OA
Osteoarthritis continues to be an important topic in equine practice due to its far-reaching consequences.
“According to the American Horse Council, the horse industry has a total impact of more than $100 billion on the U.S. gross domestic product,” relays David Frisbie, DVM, PhD, Dipl. ACVS, a leading researcher in the field of osteoarthritis based at CSU’s Gail Holmes Equine Orthopaedic Research Center.
Osteoarthritis resulting in loss not only impacts the horse and owner, but also the more than 4 million people associated with the industry, including trainers, service providers, and associated business owners.
“Treatment costs for OA include those direct out-of-pocket expenses (i.e., treatment and related costs), plus indirect costs such as lost income due to time spent on the affected horse instead of working, lost leisure time, and increased time and expenditures managing the patient with OA,” says Frisbie. “Together, these direct and indirect costs accrue, particularly with horses that develop OA at a very young age.”
Osteoarthritis is a progressive disease with no known cure. This means that once a horse develops it, OA will slowly progress for the remainder of the horse’s life. Treatment invariably will be necessary at some point during an affected horse’s life to manage pain and discomfort, control swelling, prolong the horse’s athletic function (which can include competing or simply trail riding), and maximize lifespan. At present, a multimodal treatment approach is suggested. This includes:
- Pain management via administration of non-steroidal anti-inflammatory drugs (NSAIDs) or corticosteroids;
- Intra-articular medications (hyaluronic acid, polysulfated glycosaminoglycans);
- Intramuscular polysulfated glycosaminoglycans;
- Weight management;
- Non-weight-bearing exercises (e.g., swimming) and physical therapy;
- Dietary modification (adding omega-3 fatty acids);
- Oral joint health supplements (OJHSs) including glucosamine, chondroitin sulfate, methylsulfonylmethane (MSM), avocado/soybean unsaponifiable extracts (ASU), etc.
Causes of Osteoarthritis in Horses
OA affects the joints of the horse, resulting in the slow progression of destruction to the cartilage lining the ends of the bones. It can affect one or multiple joints and can vary in severity.
This joint disease with multifactorial causes results in the progressive degradation and destruction of articular cartilage: the very thin layer of highly specialized connective tissue lining the ends of the long bones where they join. In young horses, OA is predominantly trauma-related.
“Trauma can damage joints in a number of ways, but can be categorized into two major pathways, explains McIlwraith: “Abnormal forces on normal cartilage, or normal forces on abnormal (diseased) cartilage.”
For example, repeated cycles of athletic trauma, loss of stability or development of joint incongruities (e.g., secondary to fractures, ligament injuries, etc.), and remodeling and microfracture in the bone underlying the articular cartilage can all negatively impact normal articular cartilage. Similarly, normal forces on cartilage damaged via synovitis and capsulitis (i.e., inflammation of the lining of the joint and the capsule overlying the joint, respectively), the normal aging processes, or conditions such as osteochondrosis (failure of the bone that underlies articular cartilage to mineralize; can lead to osteochondritis dissecans, or OCD) can equally and negatively affect the cartilage in joints.
“Regardless of the underlying cause, the result is the physical breakdown of articular cartilage culminating in a hot, swollen, painful joint and loss of function,” he says.
Evolution Of Osteoarthritis
November 18, 2010, Author: David Ramey
When recognized in individual joints, OA is so well-known that it’s even been given specific names, e.g.,
- “Ringbone” when seen in the pastern (from the “ring” of bone around the joint that can be seen in more severe cases), or
- “Bone Spavin” when seen in the hock (“spavin” apparently comes from a Middle French verb meaning, “to hop like a sparrow,” which, if you’ve ever seen a severely affected horse, is right on).
The joint, where two bone ends meet are lined with cartilage, providing a smooth, almost frictionless, gliding surface. Inflammation (the “-itis” in arthritis) releases chemicals that breakdown the cartilage. As the cartilage is destroyed, the underlying bone becomes involved in the process. When bone becomes inflamed, it produces more bone (which is one reason why fractures can heal). But when bone is produced in a joint, movement becomes restricted, and painful.
OA is a huge problem in medicine of any species. Medicine’s biggest questions include, “Why do bones and joints deteriorate in some individuals?” In osteoarthritis, there is a complex interaction between the tissues of the joint that plays a significant role in starting, and/or continuing, the disease. No one completely understands all the factors that are responsible for starting the breakdown and loss of the joint tissues. Because no one can answer the first question, the second obvious question, “What can be done about it?” has no “right” answer, either.
In some cases, there are hints to answers for the first question. Trauma, infection, and inflammation in joints can lead to breakdown of the joint tissues, especially the cartilage that covers the ends of the bones.
In some cases, however, OA develops for no apparent reason. While we can understand how an infected joint develops arthritis, some horses develop it for no apparent reason. It’s maddening actually. If all horses that jumped high fences developed OA, you might be able to understand that jumping high fences causes trauma, trauma causes joint breakdown, and joint breakdown results in OA. However, all jumping horses “don’t” develop OA – there must be some factor(s) in certain individuals that cause the problem.
OA is usually recognized when horses being to limp, or perform poorly. Early cases may be identified by thorough physical examination, anesthesia of affected joints (a “joint block”), and/or X-rays. Identification of the problem is often the easy part – what’s hard is figuring out what to do about it.
OA does not necessarily mean that your horse’s career is over, but it might mean that you (and your horse) have to learn how to best live with the problem. Given that horses don’t complain, and try to do the best they can with what they have, that’s sometimes easier for the horse than it is for the owner!
Check out the pages under “Lameness Therapeutics” for information about treatments that may be available for horses with OA.
Symptoms of Osteoarthritis in Horses
Pain will be present when a horse displays signs of lameness. It may be minor to begin with and worsen as the disease progresses. Upon the beginning of exercise, the horse may be stiff, then warm up to it. A horse may be reluctant to perform certain activities, such as jumping. Cold damp mornings may produce stiffness, lameness and reduced range of motion in the joint.
Diagnosis of Osteoarthritis in Horses
If a horse is exhibiting lameness, has swelling of the joints and is reluctant to move as it once did, contact a veterinarian to observe the horse at trot to evaluate what joints are affected. Injecting a shot of local anesthetic into the joint and watching for any improvement will enable the veterinarian to confirm what joint is causing the lameness. Using radiographs (X-rays) will also show which joints are affected and how badly. Though the images may show narrowing of the joint space resulting from cartilage destruction, or show a bone spur formation, or changing density within the bone, it is unable to show the cartilage. The use of a tool called an arthroscopy, which is a minute camera inserted into the joint, will show the cartilage and any damage done to this area. This process is expensive and involves surgery with the risks of anesthetizing the horse.
Treatment of Osteoarthritis in Horses
Management or preventative methods are the only course of action, as OA is incurable. A consultation with your equine veterinarian will provide a definitive diagnosis; supplementation or cold and heat therapy. Although treatment cannot reverse this disease, it may help delay further development of it. A treatment plan aimed at reducing the pain will enable better movement of the joint. Rest alone may not be enough.
The medical treatment of OA in a horse is one of the most utilized therapeutic regimens in the equine practice. It is important to understand the anatomy of synovial joints and the pathophysiology of the disease process to treat OA adequately. Once a thorough understanding of the disease process is known, the proper combination of systemic Nonsteroidal Anti-Inflammatory Drugs (NSAIDs), intraarticular steroids, viscosupplementation and chondroprotectants can be used to treat the disease and inhibit further progression of degenerative changes to the cartilage surface.
Administration of anti-inflammatory drugs–orally, topically, intravenously, or intra-articularly–remains a mainstay in OA management. Injecting anti-inflammatory corticosteroids intra-articularly is also an extremely common treatment method, but McIlwraith says, “Not any old steroid will do the trick”.
McIlwraith continues: “Marked beneficial effects have been noted after using betamethasone esters (trade name Celestone) and triamcinolone acetonide (trade name Vetalog), and deleterious effects have been identified when methylprednisolone acetate (trade name Depo-Medrol) is injected.
Despite widely relaying this finding, methylprednisolone acetate continues to be an all too commonly used steroid in horses with OA that will ultimately prove to expedite loss of articular cartilage, loss of function, and loss of the horse.”
Both betamethasone and triamcinolone can be used alone; however, it is common practice to use a combination of steroid and hyaluronic acid. Frisbie and colleagues revealed in studies that the product used (Hyvisc), injected 14, 21, and 28 days after surgically inducing OA, had disease-modifying effects on OA.
“Similar results were obtained with intra-articular polysulfated glycosaminoglycans, supporting the use of this product as well in horses with OA,” notes Frisbie.
“NSAIDs that inhibit the enzyme cyclooxygenase-2 (COX-2) such as firocoxib are associated with fewer side effects than Bute, which inhibits COX-1,” says McIlwraith.
The potential negative side effects from the COX-1 inhibitors spurred the development of topical NSAIDs, including the U.S. Food and Drug Administration (FDA) approved product containing 1% diclofenac sodium (trade name Surpass). This product, applied topically to the skin overlying one or more joints, does not appear to have the negative side effects seen with some orally administered NSAIDs. Given the low systemic absorption of this product, clinicians expect fewer potential side effects than with orally administered NSAIDs.
“Using an experimental model of OA, the diclofenac cream had both symptom and disease-modifying effects, meaning that it improved clinical signs of disease and slowed the progression of OA,” says Frisbie.
The equine practitioner is faced with many choices for controlling inflammation in OA.
Caution Required With Some NSAIDs
Oral NSAIDs are a mainstay in the management of osteoarthritis (OA) in horses.
A veterinarian may prescribe NSAIDs, such as Phenylbutazone (Bute) which is a pain killer that also helps alleviate inflammation. Used in moderation, it can help during the initial stages of the disease but is considered a short-term remedy as it produces negative side effects over prolonged use. While many horses will tolerate Bute, serious and potentially life-threatening side effects can occur, such as gastric ulcers, kidney dysfunction, and right dorsal colitis (diarrhea). According to experts, there is extreme variability in how some horses tolerate Bute, even when administered at recommended doses, while other horses cannot even tolerate short-term administration of the drug.
Firocoxib, a COX-2 inhibitor, is reportedly a safer NSAID than Bute.
Another option for managing OA is the use of a topical NSAID, which is only minimally absorbed systemically, but can ameliorate the clinical signs of osteoarthritis.
–Stacey Oke, DVM, MSc
Going the Extra Mile
In addition to the above-mentioned approaches, several emerging therapies for equine osteoarthritis are either newly available or on the horizon. The available data regarding these techniques was reviewed by McIlwraith during his presentation at WEVA and are summarized here.
Autologous conditioned serum (ACS) (trade name IRAP, which stands for Interleukin-1 Receptor Antagonist Protein) This commercially available tool involves using the horse’s own blood to generate “conditioned serum” after incubating the blood sample with specially designed beads. This serum is enriched with growth factors and anti-inflammatory mediators, such as interleukin-1 receptor antagonist (IL-1ra). The clinician then injects the conditioned serum intra-articularly. Investigators performing studies at CSU demonstrated both symptom and disease-modifying effects. IRAP is also used for soft tissue injuries, but when it comes to joints, it is primarily indicated post- surgically (e.g., after removal of articular chip fractures) or in horses with OA that are no longer responsive to intra-articular injections of hyaluronic acid and Vetalog. Still in its early stages, IRAP shows a promising treatment for the early to moderate cases of OA.
Platelet-rich plasma (PRP) This is a fraction of whole blood that contains a concentrated source of platelets, which are microscopic storage facilities for a variety of growth factors that facilitate healing. This treatment is also commercially available, but clinicians primarily use it in the management of soft tissue injuries and skin healing. No controlled studies evaluating PRP in OA have been conducted.
Gene therapy with IL-1ra This agent is an inhibitor of the inflammatory mediator IL-1. Frisbie and colleagues have been working on inserting the IL-1ra gene into a virus to deliver high doses of the IL-1 inhibitor into joints with OA.
“We are hoping that this technique, referred to as gene therapy, will effectively arrest OA in the horse and will be a clinical reality in the near future,” relays Frisbie.
Extracorporeal shock wave therapy (ESWT) Scientists studied ESWT using an experimental model of osteoarthritis. It appears to be useful in decreasing synovial membrane and joint capsule inflammation, and it improves signs of OA in affected horses.
Physical therapy and rehabilitation While widely recommended and utilized throughout the industry for horses with musculoskeletal injuries, little data is available supporting the presumed beneficial impact of physical therapy on OA. To remedy this, a study is currently under way at CSU using an experimental model of OA to assess the effect of underwater treadmill use on OA. “We anticipate data to be available in the next year,” says Frisbie.
Oral Joint Health Supplements
According to the latest market surveys, Oral Joint Health Supplements (OJHS’s) are the most popular nutritional supplements purchased for horses. 15% to 27% of equine supplements are purchased from veterinarians, while more than 60% of equine supplements are purchased from tack shops, saddleries, online, or via mail order.
Scientific studies and independent laboratory tests have revealed that a preponderance of poor-quality OJHS’s are on the market and are, at first glance, largely indistinguishable from products more likely to be safe and effective.
In addition to being an unnecessary expense, poor-quality supplements are a potential threat to your horse’s health. For more information on OJHSs and the ACCLAIM system for discerning OJHS supplement quality visit www.TheHorse.com/11958.
Cure for Equine Osteoarthritis Eludes Researchers
Osteoarthritis (OA), the painful deterioration of articular cartilage lining the ends of long bones, continues to be a problem for athletic horses. Despite decades of intense research in various species, most notably horses and humans, a cure for OA remains elusive.
In a recent effort to put the kibosh on OA joint pain, an elite team of orthopedists joined forces and compared the tried-and-true “microfracture” technique with a “bone marrow clot” strategy. In a nutshell:
- Both techniques were designed to treat full-thickness defects or tears in the articular cartilage, meaning the defect reaches the subchondral, or underlying bone. Cartilage has limited repair capacity, presumably due to the lack of blood supply, as the subchondral bone supplies nutrients to the cartilage layer.
- Microfracture involves creating tiny fissures in the subchondral bone to prompt the release of stem cells and other regenerative factors from bone marrow. Clinical results have varied, from full return to function to continued disability. Failures could be due to compromised subchondral bone following microfracture.
- In lieu of traumatizing the subchondral bone, another approach involves placing a sample of bone marrow aspirate, presumably containing stem cells, directly into the cartilage tears to stimulate healing. In this study, harvesting bone marrow cells from the patient, concentrated using a commercial system, were then placed directly into the cartilage defects.
- Both approaches are minimally invasive using a standard arthroscope.
Researchers found that both techniques achieved similar outcomes a year after surgery. Specifically, magnetic resonance imaging (MRI) revealed that regardless of the approach, all cartilage defects healed with fibrous or fibrocartilaginous tissue rather than normal, healthy articular cartilage.
“The researchers suggested that the concentrated bone marrow aspirate used in this study likely did not contain sufficient stem cells to improve cartilage healing compared to the microfracture technique,” summarized Laura Petroski, B.V.M.S., staff veterinarian for Kentucky Equine Research. While the researchers modify their approach and continue their work to conquer OA, consider other approaches to minimize the occurrence of joint disease.
- “Kentucky Equine Research offers a variety of products to protect joints in healthy horses and decrease inflammation and discomfort in horses already suffering from OA,” shared Petroski.
- Learn more about KER Flex (Glucos-A-Flex in Australia) and Synovate HA, as well as the anti-inflammatory properties of EO 3 proven to benefit horses with OA.
- Need help choosing the best supplement and ensuring your horse’s diet is appropriately balanced? Contact a Kentucky Equine Research nutrition consultant today.
- *Chu, C.R., L. Fortier, A. Williams, et al. Minimally manipulated bone marrow concentrate compared with microfracture treatment of full-thickness chondral defects: A one-year study in an equine model. Journal of Bone and Joint Surgery. American Volume. 100(2):138-146.
Since the exact pathways by which OA develops in horses remain largely ill-defined, preventing OA is challenging.
“In younger, healthy horses with repeat trauma, the focus should be placed on minimizing injury and promptly treating causes of joint instability, such as intra-articular fractures, ligamentous tears, and incongruent joint surfaces (caused by OCD),” suggests McIlwraith. “Early treatment of inflammatory conditions in the joint tissues, such as synovitis or capsulitis, can delay or possibly even prevent OA.”
Prophylactic use of IM polysulfated glycosaminoglycans (PSGAGs) is widespread; but the beneficial effect of this practice remains to be demonstrated in controlled clinical trials.
“Due to the challenges associated with equine experiments, the prophylactic use of PSGAGs is not currently being evaluated,” says McIlwraith. “That said, it is agreed that prophylactic intramuscular administration is not likely to be harmful.”
Another potential (and possibly more economical) approach to preventing OA is the use of a glucosamine- and chondroitin sulfate-containing oral joint health supplement prior to injury, trauma, or development of OA. According to McIlwraith, unlike studies of PSGAGs in horses, research in dogs does support the use of OJHSs prophylactically. Specifically, dogs receiving a glucosamine/chondroitin sulfate combination product for 21 days prior to induction of an experimental acute synovitis had significantly less evidence of joint inflammation than the control group or dogs that were treated after the induction of the synovitis.
McIlwraith explains, “Similar studies evaluating the prophylactic use of OJHSs to prevent OA in horses have not been published, but OJHSs are widely used for this purpose throughout the equine industry.”
Overall Course Of Action
Though much depends on the severity of the disease in the horse’s joints, treatment should be aimed at reducing the further development of the disease and to reduce the pain. Treatment will not cure a horse, but it can lead to a relatively comfortable life. Each horse reacts differently to treatments, so it may take time to find what works best for each specific horse. If the disease is in its early stages, taking precautions such as heat therapy on the joints before exercise to loosen the joint will help, as will cold therapy applied after exercising (such as cold hosing of the joint). Magnetic boots are said to increase the circulation at the site encouraging free movement and healing. It may end a career in racing or jumping, but your horse will comfortably live out his days.
It is important to recognize that any horse can develop OA and that each horse owner’s and veterinarian’s approach to treating or preventing OA will vary. Even though OA is incurable, it does not mean that OA is unmanageable.
“There are some viable options for slowing the progression of OA, particularly in young horses with ambitions to remain athletes for as long as possible,” summarizes McIlwraith.
About the author:
Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she has worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.
Posted by Stacey Oke, DVM, MSc Apr 1, 2010
Combination of 5 OA Articles
Title Date Author / Source Medical Treatment Of Osteoarthritis In The Horse Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401, USA. firstname.lastname@example.org ? Goodrich LR1, Nixon AJ. Evolution Of Osteoarthritis November 18, 2010 David Ramey Cure for Equine Osteoarthritis Eludes Researchers February 13, 2018 Kentucky Equine Research Staff Osteoarthritis: Not Just An Old Horse Disease April 1, 2010 Stacey Oke, DVM,MSc What is Osteorathritis 2 ? Dr Callum Turner DVM ??