Arthritis Pain Management
- Jul 1, 2000
"He knew the anguish of the marrow
The ague of the skeleton;
No contact possible to flesh
Allayed the fever of the bone."
-- from "Whispers of Immortality"
Thomas Stearns Eliot (that's T.S. Eliot of Old Possum's Book of Practical Cats fame to those of you who were daydreaming during American and English Lit) penned those words in 1920. While the language of the poem may leave open The Real Meaning of the work, it's a safe bet Eliot was not musing on the arthritis pains of the equine (even if he did write that book about cats). What a coincidence, though, that his verses so eloquently mirror the aches and inflammation of arthritic joints that plague man and beast--the heat of a tender joint, those horrible twinges that come on during wet or cold weather, the deep, stabbing pangs that occur with every hard footfall or bended limb.
Chronic arthritis was a miserable fact of life long before Eliot came and went, and remains so today. Yes, we have treatments that can assist certain types of arthritic conditions, but when it comes to the nasty stuff--chronic arthritis--cures still are elusive, with pain management offering only varying degrees of success dependant on the severity of the disease. Still, the book on arthritis pain management is a work in progress; future pages might hold the answers.
The Meaning Of Arthritis
The textbook definition of arthritis, explains lameness expert M.J. Martinelli, DVM, PhD, Dipl ACVS, clinical assistant professor, equine surgery, University of Illinois, is inflammation of the joint. "'Arth' means joint and '-itis' means inflammation," Martinelli stated. "In horses, osteoarthritis is the more common term, meaning inflammation of the bone and cartilage of the joint. However, there is a term in the human literature called 'osteoarthrosis.' 'Osis' means 'disease of.' Therefore, this term means a disease affecting the bone, cartilage, or surrounding soft tissues in a chronic way. Although possibly more accurate, it is rarely used when dealing with horses. More practically in the equine industry, the term arthritis is usually associated with any degenerative condition associated with a joint," he said.
Researcher and equine osteoarthritis expert Wayne McIlwraith, BVSc, PhD, Dipl. ACVS, head of Colorado State University's Equine Center, explained further. "Arthritis is a very general term meaning inflammation in the joint. There are various types. Arthritis in the horse ranges from inflammation of the synovial membrane and fibrous joint capsule (which we talk about as synovitis and capsulitis), through intra-articular fractures and ligament injury, all the way through osteoarthritis. Osteoarthritis is when you have progressive loss of articular cartilage. It's what you end up with if you have too severe of an initial trauma, or your initial treatment is not effective. Osteoarthritis is the end of the line."
Another well-known form of arthritis is rheumatoid arthritis, a disease of the immune system that causes the immune system to attack healthy joint cells, creating inflammation and debilitating pain, but this is a people problem. "We think there are some cases in horses where there is an autoimmune joint problem, but it's rare in horses," Martinelli stated.
"Regular" arthritis occurs by other means. "Arthritis can be caused by one of two general pathways," Martinelli said. "One is informally known as the 'acute traumatic' pathway. This usually involves some kind of acute trauma such as an articular fracture or direct damage to the articular cartilage. The classic example is a performance horse that takes a bad step during competition. If the articular surface is disrupted, joint dysfunction develops, which can lead to full-blown arthritis.
"The other general pathway is known as the 'progressive degenerative' pathway. This is by far the most common form seen in athletic horses of all breeds and uses. It is also very common in humans. It results from years of normal wear and tear on the articular surfaces of the joints. Debilitating arthritis is common among retired human professional athletes, just as it is often seen among our athletic horses."
Although arthritic symptoms are common in older performance horses, the disorder can strike at any age, even in foals. "For example, it can occur in foals after a severe bout of infection in their joints, or in a 2-year-old with poor conformation that is not corrected in the first six months or so of life," Martinelli said. "More classically, progressive degenerative arthritis occurs at some time after the initiation of the athletic career, although it is most common in horses in their 'teens.' "
Several factors can predispose a horse to arthritis, including genetics, environment, infected joints as a foal or adult, an articular fracture, inadequate training, or inappropriate shoeing or foot care.
"There are some aspects, such as less than ideal conformation, which may be inherited to some degree or another," Martinelli noted. "As for environment, this could relate to anything that could create physiological stress in the articular environment and the cartilage."
Is It Arthritis?
Diagnosis is based on clinical signs, history, physical exam, and/or diagnostic testing.
"First and foremost, veterinarians will begin with a history of the problem and a full physical examination," Martinelli said. "After a general physical examination, the musculoskeletal system may be examined in depth for signs such as heat, joint effusion, or pain on manipulation of the joints."
Following this, a lameness examination will be carried out. "The horse may be trotted in hand, lunged, or ridden," explained Martinelli, who added that flexion tests normally are part of this exam. "Flexion tests involve stressing a joint to its maximum range of motion and holding it for a period of time, such as one minute, before trotting the horse off again. In this way, some subtle 'sorenesses' can be detected earlier."
Once lameness has been localized to one limb, the veterinarian might perform regional anesthesia (nerve blocks) in an effort to desensitize nerves or joints. "By working in a systematic manner with the local anesthetic, the veterinarian can determine exactly where the pain is emanating from," Martinelli stated.
At this point in the examination, the veterinarian likely will obtain radiographs of the area suspected to be causing the problem. "Radiology has been the imaging standard for many years for detecting arthritic changes around joints," noted Martinelli. "Bone spurs, or osteophytes, are considered an obvious sign of arthritis; however, not all horses with joint pain will have radiographic evidence of arthritis. In fact, it is not uncommon nowadays to find lame horses with no evidence of radiographic disease. In these cases, the horse may show all the classic signs of an articular problem, yet no concomitant radiographic changes. For example, the horse may be lame in the left forelimb, show articular effusion in the fetlock, with the lameness increasing dramatically when the fetlock joint is flexed. But even though there is no radiographic evidence of arthritis, based on the clinical examination and results of regional anesthesia, the horse is suffering from an articular disease."
While radiology often cannot detect early arthritic changes, nuclear scintigraphy might be able to produce a more accurate diagnosis. "Nuclear scintigraphy is a metabolic imaging modality that relies on blood supply and remodeling bone to produce an image," Martinelli said. "A safe radioactive compound is labeled with a bone-seeking agent and injected intravenously. A special gamma camera then is used to detect the radiation coming from the horse and a computer generates a 'map' of the horse's leg to determine where the problems or 'hot spots' are located. Nuclear scintigraphy is much more sensitive than radiography at detecting very minute changes in bone, especially in relation to stress fractures or early arthritis. It is becoming very common to find horses that have a 'hot spot' near a joint showing clinical signs of articular disease without any radiographic changes."
Arthroscopy is another effective way to diagnose early joint disease.
"When the problem has been localized to a joint, but no changes are seen on the radiographs, it is becoming more common to use the arthroscope to visualize the articular surface of the joint to look for damage to the articular cartilage," said Martinelli. "It should be noted that articular cartilage cannot be visualized in any other way, because it does not show up on radiographs or nuclear scans." Adds McIlwraith, "Diagnostic arthroscopy is still the gold standard to define exactly the damage in a joint."
Other diagnostic aids can be used to determine damage. "A conventional synovial fluid analysis will indicate the degree of inflammation within the joint," continues McIlwraith. "Ultrasound is useful for diagnosing ligament damage and fibrous joint capsule damage."
The key to a successful outcome is early detection. "The sooner the problem is addressed, the more likely it is that treatment is successful," Martinelli emphasized. "If the cause is an acute, traumatic episode without permanent structural damage, then the prognosis could be excellent. In cases of acute traumatic incidents resulting in permanent damage to the articular surface, the chances for recovery are slim and treatment may consist of ameliorating the clinical signs for as long as possible."
"With synovitis and capsulitis, a lot of those cases are reversible," adds McIlwraith. "You treat the problem and it goes away and does not necessarily come back."
Martinelli said that in the vast majority of cases--meaning those that are degenerative--prognosis often depends on such factors as the age of the horse at the time of onset, the joint or joints affected, the use of the horse, and even the breed or temperament.
"For example," he noted, "Standardbred racehorses are often very tolerant of arthritis, whereas some other breeds may not be. Similarly, an 'old campaigner' in any breed who finally begins to feel the effects of all those years of competition may be less likely to feel the effects of arthritis than a very young horse who has done very little in its career before the onset of joint pain. For any of these case scenarios, early detection is the key to a successful outcome. This usually means routine examinations by your veterinarian, especially for those horses competing at a high level of competition."
"Once you get cartilage degeneration, it's permanent, so you don't get as dramatic a response," McIlwraith said.
Generally, the earlier the treatment is introduced, the greater the chance of recovery. Martinelli observed that horse owners are becoming savvier in seeking an early diagnosis. "In small animal practice, most dogs are presented for osteoarthritis long after the disease process is well developed. The clients may notice some stiffness or lameness for a period of time, perhaps even years, before seeking treatment. It is not until the dog has more significant difficulties, such as inability to go up stairs or get into the car, that veterinary attention is sought. In these cases, the disease process is usually so far advanced that it may be impossible to cure and difficult to treat. In the human field, medical doctors are often faced with the same situation because human patients are often reluctant to seek medical care for that 'old football injury.'
"But in the equine industry, it is becoming more common for clients to present their horse very early in the 'soreness' cascade. In fact, many clients will even report that their horse is not 'lame,' he's just not 'quite right.' An early approach to these cases of equine articular derangement may mean a better chance at a cure."
In acute cases of joint inflammation, rest and non-steroidal anti-inflammatory drugs (NSAIDs) can be beneficial, said Martinelli. NSAIDS include phenylbutazone (bute), naproxen, and flunixin meglumine (Banamine). They can be administered orally or by injection, and contain pain relieving and anti-inflammatory properties.
"For chronic arthritis, polysulfated glycosaminoglycans (PSGAGs or GAGs) can be given intramuscularly, intra-articularly, and orally, while hyaluronic acid (HA) can be given intra-articularly or intravenously," Martinelli said.
GAGs can protect degenerating cartilage. Adequan is a GAG product available in intramuscular and intra-articular form. HA (also know as sodium hyaluronate) can provide pain relief, anti-inflammatory response, inhibit damaging enzymes, increase the viscosity of synovial fluid, and encourage production of natural sodium hyaluronate in the joint. Normal joint fluid should be viscous in order to aid in shock absorbing and lubrication of the articular tissues. The product Legend is the only intravenous form of HA, and it also is available in an intra-articular form, as are many other products.
Corticosteroids and the newer oral products such as oral glucosamine and glycosaminoglycans (an example is Cosequin, which is a mixture of chondroitin sulfate and glucosamine), also might help, said McIlwraith. Corticosteroids are effective for pain relief, reducing the inflammatory mediators that can cause cartilage degeneration. "We have validated the usefulness of corticosteroids, hyaluronic acid, and Adequan pretty well, but we do not have good data as to the effectiveness of the oral glucosamines," he said.
McIlwraith cautions that the lack of data does not mean oral glucosamines don't work. "I take an oral glucosamine/glycosaminoglycan preparation myself for osteoarthritis in the hip, and I think it helps. But there's just been no controlled work done in the horse, and that needs to be done," he said.
MSM (methylsulfonylmethane), a product closely related to DMSO, is used by some for inflammation, but no research has been done on it for joint disease in the horse, McIlwraith said. However, according to a recent press release, a double-blind study of 16 human patients found that more than 80% of those who took 2,250 milligrams of Lignisul MSM daily for six weeks reported an 82% average improvement in pain relief, compared to an 18% improvement reported by patients receiving the placebo treatment.
The effectiveness of alternative therapies such as acupuncture, chiropractic, and massage therapy for arthritic pain relief is unknown. "We don't have a lot of objective data," Martinelli notes. "My approach is we don't have a cure for arthritis, but as long as there are no side effects with those procedures, I have no problem in trying those things. There are a lot of cases where you're going to get a lot of relief from massage or something that helps the muscles out while you're treating the primary problem if clients want to seek out these treatments."
McIlwraith said he hasn't seen any controlled studies in the horse. "But that doesn't mean that these modalities don't have a place. I'm not qualified to comment, and it's not part of the treatment protocol that I use for those problems. I've seen acupuncture, massage, and chiropractic used for vertebral and muscle problems, but not for the joints, per se."
Fortunately, there are veterinary studies underway and planned for the near future examining new arthritis or pain-relief treatments in the horse and other species.
"Probably the most significant advances in the treatment of osteoarthritis in both people and horses involve cartilage resurfacing research," Martinelli said. "Several investigators in particular are working on ways either to grow new cartilage cells outside of the body before implanting them into cartilage defects or surgical methods to stimulate cartilage healing. Other advances are aimed at altering genetic material in an effort to modify the disease process.
"In our laboratory as well as a few others around the world, we are concentrating on further defining the mechanisms responsible for joint dysfunction. Although the loss of articular cartilage is definitely the end stage of the arthritic course, we believe that the subchondral bone, or bone just below the cartilage, may be a very important factor in the process, especially in those cases of progressive, degenerative disease. In these horses, the bone may become harder than normal, decreasing the amount of shock absorbing capabilities of the joint and thereby increasing the amount of pressure that is placed on the articular cartilage, which may lead to serious damage."
McIlwraith reported that several equine orthopedic studies are going on at Colorado State University. These studies are focusing on the following areas:
Articular cartilage healing in an attempt to solve the problem of osteoarthritis in horses and humans. This includes removal of calcified cartilage, the ability to biopsy repair tissue arthroscopically regularly, evaluating subchondral micropicking and its promotion of articular cartilage healing, evaluating the quality of repair gained by implanting cartilage constructs made from neonatal cartilage, and cartilage grafting.
"Micropicking is basically picking holes in the bone to allow growth vectors and cells to come into the defect," said McIlwraith. "We took the technique from human orthopedic surgeon Richard Steadman and evaluated it in the horse and showed that the subchondral microfracture enhances the amount of repair tissue you get in the cartilage defect. I'm already using subchondral microfracture in some clinical cases where it's appropriate. It's all done arthroscopically. The horse is standing within 15 minutes after surgery and is back to full training within two to six months, depending how severely affected it was."
- The role of micro-damage to subchondral bone in traumatic bone disease. Several fractures and injuries start as microfractures in the subchondral bone. The research goal is to develop methods of detecting this damage before it becomes irreversible. Work is continuing in the development of serum markers of early bone damage to determine if detection of bone damage is possible prior to any type of fracture; evaluating joint surface mapping in the carpus and fetlock via MRI; quantitative computerized tomography for detecting early bone changes; and developing a portable quantitative CT for practical application.
- Development of fluid markers (in synovial fluid, serum, urine) to detect early articular cartilage and subchondral bone damage in joint disease, thus permitting early treatment. Also, looking at changes in serum markers with age in the horse, changes in developmental orthopedic disease, and changes in markers with exercise.
Developing molecular biology techniques to document early molecular events in arthritis and establish therapeutic techniques to treat them. Using techniques such as gene therapy specifically to inhibit disease processes sufficiently early would preclude the need for pain-killing drugs currently used. Evaluating how much arthritis-inhibiting effect can be gained from implanted genetic material. Examining the inoculation of other desirable genes that might decrease osteoarthritis or help cartilage healing.
"Our work with gene therapy is the first demonstration in gene therapy as a treatment showing a clinical response in arthritis in any species," McIlwraith noted. "We cloned the gene sequence for an antagonist of interleukin-1 and placed that gene sequence with a viral vector into the joint. We were able to combat the development of osteoarthritis in injured equine joints."
- Continued evaluation of new treatments for traumatic arthritis, including corticosteroids, hyaluronic acid, polysulfated glycosaminoglycans, oral glycosaminoglycans, and metalloproteinase (MMP) inhibitors. "MMP is the final enzyme in the cascade that degrades cartilage," explained McIlwraith. "The trouble is that MMPs are important for normal tissue remodeling processes, so I don't know if they will be appropriate in the young animals. There is already some data to insinuate side effects. Clinical trials will begin in the dog, then we are moving on to the equine."
Evaluation of other factors that contribute to traumatic injury including conformation and racetrack surfaces.
- Studying the significance of radiographic lesions in terms of subsequent musculoskeletal problems.
Happily Ever After?
While there is not yet a satisfying ending for the tale of chronic arthritis pain management, the scribes promise that future chapters will lead to a happier resolution. For sure, there is great interest in both human and veterinary medicine in identifying causes and cures for this troubling disease.
Stay tuned for the next installment!
As of yet, there is no sure-fire way to prevent the occurrence of arthritis. However, it might be possible to lessen the risk. "It is important to stress that overall good care is always the first step in maintaining your horseï¿½s health,
Martinelli emphasized. "In relation to arthritis directly, probably the most important thing to remember is that good training practices are designed to improve not only cardiovascular and pulmonary fitness, but training also helps strengthen the components of the musculoskeletal system such as the muscles, bones, tendons, and ligaments. Increased general fitness decreases the amount of fatigue experienced by the horse during competition, thereby decreasing the chance for fatigue-induced injuries. Strengthening of the musculoskeletal tissues, and particularly those of the articulation, diminish the chance of damage occurring during competition. Routine examinations by your veterinarian may help detect a subtle problem before it becomes more severe."
He noted that most performance horses experience soreness at some stage of their career.
"Not all of these perceived sorenesses will develop into pathological lameness or arthritis," he cautioned. "For the most part, however, osteoarthritis is a part of athletic activity."
Antagonistï¿½A chemical that acts within the body to reduce the physiological activity of another chemical substance.
Arthritisï¿½Inflammation of the joint.
Articularï¿½Of or relating to a joint.
Articular cartilageï¿½Cartilage found within the joint structure.
Cartilageï¿½A firm, elastic, whitish type of connective tissue.
Diagnostic arthroscopyï¿½Visual examination of a joint with a special surgical instrument.
Interleukin-1ï¿½An interleukin is produced by synoviocytes, chondrocytes, and some types of white blood cells that regulates immune responses and mediates other biological processes (as the onset of fever) usually associated with infection and inflammation.
Jointï¿½The point of contact between elements of an animal skeleton whether movable or rigidly fixed together with the parts (as membranes, tendons, ligaments) that surround and support it.
Joint capsulesï¿½Thin, sac-like structure that envelopes a joint and contains within it all the elements of the joint (articular cartilage, synovial membrane, synovial fluid, etc).
Osteoarthritisï¿½Arthritis marked by chronic breakdown of cartilage in the joints leading to pain, stiffness, and swelling. Also called degenerative joint disease.
Subchondralï¿½Situated beneath cartilage.
Synovial fluidï¿½Joint fluid, the material that lubricates the joint surfaces, which secrete synovial fluid.
Synovial membraneï¿½Lining membrane of the joint.
About the Author
Marcia King is an award-winning freelance writer based in Ohio who specializes in equine, canine, and feline veterinary topics. She's schooled in hunt seat, dressage, and Western pleasure.
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