AAEP Convention 2006: Lameness
Oral Joint Supplements: Do They Work?
In 2005, nutraceutical sales reached more than $1 billion for companion animals. That number is expected to double in the next three years. To veterinarians, this is a disturbing trend for an industry that, for the most part, is unregulated by the FDA and has little scientific basis.
Wayne McIlwraith, BVSc, PhD, FRCVS, DSc, DrMedVet (hc), Dipl. ACVS, Barbara Cox Anthony Chair and Director of Orthopedic Research at Colorado State University (CSU), expressed his concerns about the limited information on oral joint supplements, particularly chondroitin sulfate and glucosamine. He said it is unclear how and when to use supplements because many have low bioavailability, poor quality, low recommended doses, and a lack of scientific evidence supporting their effectiveness. He presented this material on the behalf of Stacey Oke, DVM, MSc, and Scott Weese, DVM, DVSc, Dipl. ACVIM, who could not attend the meeting.
When faced with joint problems, veterinarians' treatment goals include controlling clinical signs, minimizing pain, and improving joint mobility. McIlwraith said he would add "prevention of advanced degradation of the articular cartilage" to those goals.
"It's certainly a major quest of our Orthopaedic Research Center at CSU that we try to find disease modifying instead of symptom modifying drugs," McIlwraith said.
He spoke briefly about some of the adverse effects associated with non-steroidal anti-inflammatory drugs, as well as some corticosteroids.
"Methlyprednisolone acetate (which is a corticosteroid) causes degradative changes in the cartilage--other corticosteriods do not," he said.
"This industry is proceeding along somewhat independent of veterinarians," he continued. "That's one of the frustrations that we have. We get left out of the loop, at least at this stage, on diagnosis and recommendations for best therapies."
Scientist should concentrate on this industry to regulate inaccuracies and false claims. In 2005, nutraceutical pet sales exceeded $1 billion and that number is expected to grow 15-25% per year at least until 2009. At this rate of growth, McIlwraith said industry sales will be around $2 billion by 2009. His concern lies in the fact that "what we've showed scientifically has nothing to do with it so far. Most of the growth is based on advertising."
What Are Nutraceuticals?
"The term 'nutraceuticals' is not recognized by the FDA in veterinary medicine. It was born from the words nutrition and pharmaceuticals," Mclllwraith said. "A nutraceutical is any substance that is a food or part of a food and provides medical or health benefits including the prevention and treatment of disease.
"The term covers a wide range of products, and it's hardly specific," he said. "The FDA Center of Veterinary Medicine considers all veterinary nutraceuticals products as unapproved drugs, as most of these products claim to treat or cure disease."
He noted that policing the nutraceuticals market is a low priority for the FDA. These lax regulations contribute to the production of poor quality products, such as a product with low levels of glucosamine compared to what the label states. One study showed that only two out of 14 (14%) products contained the amount of ingredients stated on the label.
"Another problem with quality is the recommendation of subtherapeutic doses," he explained. "The current recommended dosage is 20 mg/kg. A lot of products and dosage recommendations don't meet that requirement.
"A third problem with quality is that some products can be contaminated with harmful materials such as lead, pesticides, and DMSO (dimethyl sulfoxide, an anti- inflammatory)," noted McIlwraith. "Another issue is products with confusing or incorrect label claims as the amount of ingredient per scoop weight. The amount of active ingredients could not possibly fit into the serving size."
False or vague product claims are another problem horse owners must face. McIlwraith said, "We have problems with product claims: 'Goes to work immediately to give your horse maximum joint mobility and flexibility.' I know that's never been demonstrated scientifically, at least not in published medical journals. 'Superior, one-of-a-kind, therapeutic, nutraceuticals, that provides extra-strength, full-spectrum support for your horse'. Now, I've been working in joint disease for a long time, and I don't know what 'full-spectrum joint support' is."
Glucosamine is a building block for articular cartilage, and it is a source of keratin sulfate and chondroitin sulfate. There are three forms of glucosamine (sulfate, hydrochloride, or N-acetylglucosamine), which are widely regard as safe.
Identifying quality products The gold standard is "they have to have in vivo evidence," McIlwraith said. "In in vitro studies, the glucosamine doesn't go through the gut." This means the bioavailability of the product can be uncertain because researchers haven't demonstrated its ability to travel from the digestive tract to the joint.
Bioavailability "There are two in vivo trials that have looked at glucosamine in the horse," McIlwraith said. "One study induced synovitis (inflammation of the synovial membrane) in clinically normal horses and showed that there was no effect." Another study showed that in 25 cases improvement was shown, but no control horses were available to compare the study horses to.
McIlwraith said that there have been several joint supplement efficacy studies in humans. However, these studies are hardly useful for horses because the equine's intestinal tract is very different.
While glucosamine supplementation is very common, there is currently little information to assist veterinarians in deciding when and how to use these products. Low bioavailability of oral glucosamine, poor product quality, low recommended doses, and a lack of scientific evidence showing efficacy of popular oral joint supplements are major concerns.
Shock Wave Effects On Nerve, Vascular Tissue
Some human and other mammalian studies have shown that extracorporeal shock wave therapy (ESWT) has adverse effects on vascular and nerve tissues, but this might not hold true for these structures in the horse. There have been some studies on ESWT's effects on equine tendons and other large soft-tissue structures, but few studies have been done on the effects on vascular and nerve structures in the horse.
In a recent study presented at the 2006 American Association of Equine Practitioners convention in San Antonio, Texas, held Dec. 2-6, researchers used non-focused ESWT on the vascular bundles in the pasterns of one forelimb and one hind limb in each of five ponies. Adjacent vascular bundles were used as control areas. Each limb was treated with 2,000 pulses at a pressure of 2.5 bars and a frequency of 8 Hz. Scientists monitored the ponies for the following 24-hour period. Then they euthanatized the ponies and took samples of the treated areas.
"The results of this study suggest that non-focused ESWT (evaluated by gross examination and histopathology-- microscopically--in adult ponies) does not have any appreciable anatomic or gross functional effect on the digital blood vessels in the short-term period," explained Mauro Verna, DVM, MS, Dipl. ACVS, currently in Argentina, who performed this study with colleagues at the University of Minnesota.
Verna explained, "No gross evidence of skin ulceration was observed 24 hours post-treatment. Light microscopic examination did not reveal any evidence of clot formation, tissue damage, or infiltration of inflammatory cells in any of the tunics (thin membranous layers of tissue). No evidence of endothelial (lining of the vessels) swelling or detachment was noted in any of the treated or control slides."
He said the difference between the human trials and the horse trials could be related to the different type of ESWT used (focused versus non-focused). However, he said larger studies are needed to better determine ESWT's effect on vascular and nerve structures.
Safely Administer Joint Blocks and Medicine
Rumors have circulated in the horse world that administering intrasynovial anesthesia (joint blocks) and intrasynovial medication in the same joint, on the same day, can result in infection within the joint. Chad Zubrod, DVM, MS, Dipl. ACVS, of Oakridge Equine Hospital in Edmond, Okla., recently took a look back at past patients that received intrasynovial blocks, medications, or both. His findings reveal that doubling up on the procedures doesn't significantly affect the chances of infection.
Zubrod found sepsis occurred in one horse out of 500 that received anesthesia alone. Intrasynovial anesthesia and medications were administered to 226 horses, none of which had an infection. Medications included hyaluronan, methylprednisolone acetate, and triamcinolone acetonide. None of the cases had antimicrobials included in their injections. On average, medications were administered 60 minutes after anesthesia.
The results came in via client surveys that asked if horses had displayed any swelling or severe lameness, or required treatment for intrasynovial infection following their injections at Zubrod's clinic. These results indicate it is unnecessary to delay treatment with intrasynovial medication following a joint block.
However, Zubrod cautioned practitioners about the risk of infection every time a needle enters an intrasynovial space. By increasing the number of times that space is entered, the risk increases as well.
"Every time you put a needle in a joint, there is risk," Zubrod said. "You have to remember the inherent risk of performing multiple intrasynovial centeses (perforations or tappings) and maintain those aseptic conditions."
Zubrod also noted local anesthetic potentially delays healing at the intrasynovial injection site and depresses the local immune system within the joint.
Jumping to a Diagnosis
Horses performing different jobs require specialized examinations for lameness, according to Philippe Benoit, DVM, French jumping team veterinarian from 1991 to 2000. Benoit presented his method for examining jumping horses.
Benoit said he likes to see jumping horses in action under saddle--warming up, going through their work, and cooling off, as some pain might be visible only in a specific aspect of the performance, as such as horse that prefers landing on one particular foot.
According to Benoit, the evaluation under saddle should be considered along with the traditional veterinary lameness exam, an exam of the environment (size of arena, footing conditions, etc.), and the rider's evaluation of the horse.
During an exam under saddle, Benoit asks the rider to warm the horse up using their normal routine. He considers the horse's bending, amplitude, gait, and stride length, and the motion of different parts of the back. He watches the horse's reaction to collection, which he noted is particularly helpful for diagnosing stifle problems. While the rider is a crucial part of an under saddle exam, Benoit stressed the rider should be skilled enough to give the practitioner the ability to evaluate the horse without interference.
Each stage of the jumping effort can be evaluated separately, Benoit said.
During take-off, check the horse's trajectory over the fence, symmetry between the horse's limbs, and look for tardiness in the front limbs. Over the jump, look at the horse's stance over the jump, considering the position of the neck and back, and the horse's way of extending hind limbs over fence. As the horse lands, observe the motion of the back and neck, see if the horse is landing on a preferred front foot, and look at the flexion and extension of lumbar and sacral areas.
Between jumps, consider whether the horse maintains its lead consistently and correctly, and whether it deviates laterally on takeoff (consistently jumping at an angle following a straight approach). Look at the horse's speed, level of collection, and quality of movement between fences.
Following exertion, watch the horse trot actively in both directions to see if anything has changed.
Considering all of these criteria while watching a horse perform as they do in competition can help practitioners pinpoint possible sources of pain. Benoit said exams of this sort can also be helpful for performance horses competing in disciplines other than jumping.
"It's very useful to do this sort of examination in other disciplines, once you know enough about that discipline and the rider's ability," Benoit said. "This is a way of communicating with people. If you see a lesion in the hoof or back, that might be the cause of non-performance, not inability."
Higher Silicate-Associated Osteoporosis Risk in Some Regions
Silicosis in horses is a respiratory condition caused by exposure to certain types of silicate dust that are found in some geographic regions. While silicosis is not a commonly diagnosed equine ailment in most areas of the country, Matthew Durham, DVM, of Steinbeck Country Equine Clinic in Salinas, Calif., said he sees cases far too often in his practice. Durham presented research he and co-author Coral Armstrong, DVM, conducted on 18 horses with clinical signs of silicosis, including numerous fractures, and bone deformities.
Silicosis is typically a chronic condition in humans causing mild to severe respiratory disease that's often accompanied by rheumatoid arthritis and lupus (a chronic autoimmune disease). In horses it causes respiratory disease, and it appears to be associated with osteoporosis (reduction of bone mass, and its associated fractures) and bone deformity. Silicosis is caused by the inhalation of certain types of silicate dust, including quartz and cristobalite. While quartz does not tend to be dusty, cristobalite is chalky and its dust becomes airborne easily, making horses in areas with high amounts of cristobalite rock particularly susceptible to the condition.
"We see silicosis in our area relatively frequently because we have the right soil type for it," Durham said. "All of the horses we have seen with these bony abnormalities live or have lived in an endemic (prevalent at all times) area."
Durham and Armstrong performed exams on 18 horses in their practice area with signs of silicosis. Of these, 17 had bone deformities including bowed scapulas (in which the scapula, or shoulder blade, arcs out from the horse's body). Fractures among these horses were also common: There were three vertebral, two scapular, five pelvic, and one maxillary (upper jaw) fracture. Additionally, eight horses had rib fractures, including one mare with 22 fractured ribs. The horses also showed significant bone remodeling typical of osteoporosis.
All of these horses were exercise intolerant. Durham said five showed respiratory distress, and researchers felt the others were exercise intolerant due to bone pain.
Durham said that all of the horses in the study group were kept in dry lots or in areas with recent construction, both of which could have caused the horses to inhale silicate dust.
These horses were all from areas of the Monterey Formation, which is a wide swath of soil containing a high level of cristobalite. Durham noted that the study cases lined up right along a ridge--including four cases from one farm--suggesting that the geographic location is the strongest risk factor for silicate-related osteoporosis.
As for treatment, Durham has found that steroids are sometimes more effective for treating the horses' bone pain than NSAIDs. Joint treatments Legend (hyaluronate sodium) and Tildren (tildronate) have also been well-received. As for the respiratory signs, steroids and bronchodilators are typically helpful, but environmental control (decreasing the horse's exposure to silicate dust as much as possible) is key, Durham said.
Durham's research on silicosis is ongoing, and he said upcoming UC Davis projects include detailed bone study, including in vivo bone density measurements, research on the U.S. Geological Survey's maps, and continued examination of the route of exposure.
Lameness and Imaging Panel
The Lameness and Imaging Panel reviewed salient features of lameness diagnosis and treatment in the horse. A panel of four experienced veterinarians, Jerry Black, DVM, of Pioneer Equine in California, Richard Mitchell, DVM, and Carolyn Weinberg, DVM of Fairfield Equine Associates in Connecticut, and David Frisbie, DVM, PhD, Dipl. ACVS of Colorado State University, were led by Greg Roberts, DVM, Dipl. ACVR, and Robert Schneider, DVM, Dipl. ACVS, both of Washington State University, in remarking on specific cases shown on video, both at regular speed and in slow motion. Each practitioner theoretically worked through each case in a methodical manner similar to what he or she would do if presented with the horse in a clinical setting.
At the time of taping, every horse was examined with a thorough gait analysis including trotting on a straight line and in circles, and the findings were summarized for the panelists. The lame leg (or legs) was identified and underwent limb manipulation, hoof tester exam, flexion tests, and diagnostic nerve blocks. The number of diagnostic nerve blocks pursued at referral hospitals depends on the cooperation of the horse and whether or not another veterinarian has diligently worked up the horse previously and referred the case for a second opinion. Conformation evaluation and hoof balance are routine components of every clinical exam.
After the moderators mentioned relevant clinical information for each case review, they asked the panel to make suggestions as to which other imaging modalities should be pursued, such as radiography, diagnostic ultrasonography, nuclear scintigraphy, or magnetic resonance imaging (MRI). The panelists discussed the significance of imaging findings that were revealed on the screen to the audience, and they discussed the findings' significance to the cases and the general athletic horse population.
All practitioners emphasized the importance of following a systematic sequence in working up a lame horse. One additional notable feature that helps identify a lame limb is the disparity in fetlock drop seen between a lame leg and the opposite non-lame leg. Slow-motion videography is useful to evaluate fetlock drop in subtle lameness cases. Also of significance is the audible difference between limb strikes of lame versus sound limbs on an asphalt surface. Weinberg encourages practitioners to watch a horse move in circles and with a mounted rider to see if this additional weight and/or specific tasks augment a subtle lameness.
A horse might not be perfectly sound, but he still might be able to perform, although a rider might observe or feel that performance is "subpar." There are benefits in performing diagnostic imaging early in suspect areas of any gait abnormality; this facilitates identification of a simmering problem before it blows into a career-limiting issue.
Sometimes a chronic degenerative process, such as proximal suspensory desmitis, changes and deteriorates over time until a horse cannot compensate further and suddenly becomes quite lame. This type of injury is common in a teenage performance athlete. Another example discussed was the development of cystic lesions in the ends of bones in a joint; such degenerative cysts can be induced by repetitive motion trauma or might be secondary to some other injury that destabilizes the joint, such as a meniscal tear in the stifle.
Several of the panelists pointed out that bone injuries are becoming more apparent with the aid of advancing imaging techniques. Proactive identification of a potentially devastating musculoskeletal injury could allow time for therapy or surgical correction.
With multiple-limb lameness, it is expedient to start working up the worst leg, then methodically sort through each problem. Weinberg noted that while many horses have a predominant lame leg, other lameness concerns and axial skeletal abnormalities have merit, so it is important to treat the whole horse. She stressed that treatment must provide comfort for a sufficient time to also prevent a horse from overloading other support structures.
All panelists reminded the audience that the time-honored treatment of 60-120 days rest in a "medical" paddock often yields information. It can be difficult to confine a horse to just a stall for extended rest periods, so a compromise is often made to place the horse in a small run or paddock to keep him relatively sane, yet quiet.
Black observed the bottom line-- regardless of the availability of advanced imaging diagnostics, it is valuable to treat a horse to see if there is favorable response to treatment. A veterinarian must plan a strategy that is based on systematic rule-outs of negative findings that narrow down the location to be treated.
Weinberg pointed out that in some cases, "If it looks like a duck...," then treatment can be implemented to target a highly suspicious problem.
All panelists echoed these sentiments, suggesting that a veterinarian can use treatment effectively as part of a diagnostic work-up. Often there are lesions that cannot be "seen" with traditional imaging techniques like ultrasound or radiography, and not every owner is able to pursue nuclear scintigraphy or MRI. Many horses have degenerative joint disease without radiographic changes. Injecting a joint with anti-inflammatory medication is a common therapy that is helpful in managing those joints that show minimal radiographic changes and no effusion (distention), yet the horse has "blocked out" sound with diagnostic anesthesia in a specific joint or regional location of the limb.
This strategy still permits surgery at a later time if there is an unsatisfactory response either in degree of improvement or sufficient duration of improvement following treatment.
It is important for an owner to carefully monitor response to therapy. For optimal owner compliance, a veterinarian should adequately discuss all available options in diagnosing a problem, and then advise the client about expectations following lameness treatment and management.
Barefoot vs Shod Table Topic
Steve O'Grady, DVM, MRCVS, of Northern Virginia Equine in Marshall, and Dan Marks, VMD, of Santa Fe, N.M., led a table topic discussion on the merits and disadvantages of leaving a horse barefoot or shod. O'Grady recognized that shoes change the structure of the hoof capsule to some degree, and he is an advocate of leaving shoes off if this works in an individual situation. However, the choice made to shoe or not depends on several variables.
When wear exceeds growth, the hoof needs protection. Not all horses can withstand being barefoot--this is dependent on breed, genetics, degree of exercise, and degree to which the feet have developed. Just because a horse is not limping is insufficient evidence that he is completely comfortable. You should also take into consideration the type of footing and the type and amount of work. For example, the requirements of hoof protection are vastly different between light trail riding on soft ground as compared to endurance competition on abrasive, uneven ground.
The horse's need for traction on variable ground conditions also dictates the choice of barefoot versus shod; traction affects safety of both horse and rider. O'Grady said shoes themselves act as traction devices as well as providing more "cup" in the foot. Marks commented that some horses are more agile and stable than others, and with normal shoes or barefoot, they can gallop and turn on surfaces that would cause other horses without traction devices to slip or fall.
Both discussed that the presence of lameness or underlying disease dictates whether a horse can or cannot go barefoot. A horse with chronic laminitis likely needs shoes to improve mechanical forces on the coffin bone and sensitive laminae. Conformational abnormalities or foals with flexural or angular limb deformities might benefit from shoes that alter forces up the limb to effect change.
A farrier in the audience remarked that he had the impression that sometimes an owner's reluctance to shoe a horse is based on a financial decision rather than about what's optimal for a horse's hooves. When removing shoes, it is important to critically evaluate the structures of a horse's feet for substance and durability. In addition, how long a horse has worn shoes has bearing on how long it might take for him to develop sole protection once the shoes are off. The hooves of a barefoot horse are better off "shaped" rather than trimmed--flares should be knocked off and the feet leveled and balanced without use of the nippers.
Marks commented that many barefoot proponents have taken an extremist view that shoes and nails start the feet on a destructive road, purporting this belief without looking at the overall historic, scientific, and physiological picture. O'Grady commented that on a deformable surface, a horse with shoes will load-share on all structures of the foot. Marks suggests that it is not always easy for every horse to go barefoot, just as many people in this world tend to wear shoes, given a choice.
One important issue that merited much discussion among the participants focused on how allowing a horse's feet to develop properly in his growing and young, athletic years affects his future soundness, with or without shoes. Hoof development, particularly for at least the first three years, is dependent on regular exercise and turnout to stimulate the foot before it is subjected to shoes and farrier tendencies. A horse raised in a controlled environment, such as in a stall or in a small paddock, has limited chance of adaptation to develop a mature and substantial foot.
Both table topic leaders and other practitioners and farriers in the room noted that regardless of the breed, there is a great difference between the feet of horses raised outside and able to self-exercise, especially on rugged terrain, compared to those contained in "controlled," non-stimulating environments. If hoof structures are poorly developed, then they will be less capable of going barefoot and, even when shod, not as ready for withstanding continuous training. To avoid sore feet, the quality of the trimming and shoeing and interval between shoeings is more critical to these horses.
The mass and strength of a horse's feet determine how well the horse can accommodate being barefoot. In addition, the surface on which a horse is housed and turned out has everything to do with how appropriately the hooves toughen. If the horse spends the majority of its time on soft footing, then it is difficult to adequately stress the hoof to acclimate and build thicker and tougher soles and a thicker bridge between collateral cartilages of the hoof wall. Alternating wet and dry spells make it more difficult for hooves to accommodate for consistently hard footing.
It might take three months of limited work on soft going to determine if an individual can remain barefoot. O'Grady noted that if a horse grows a rim of sole at the sole-wall junction, then don't yet give up on the barefoot idea, but if at 30 days the horse is still sensitive to thumb pressure in this area, he probably is not a good candidate to stay barefoot. O'Grady emphasized that the caudal (rear) structures of the hoof are typically weight-bearing structures. If a horse is uncomfortable while barefoot or if there is excess pressure on any hoof structures, then blood supply is reduced and hoof growth is limited, leading to an unrelenting cycle of discomfort and difficult-to-manage feet.
Marks noted that with sore or weak feet, it might be better to encourage the feet to remodel while in shoes. This is accomplished with trimming that encourages sole and heel growth; then attempts can be made to transition the horse to being barefoot. Sometimes it is necessary to give sufficient time--as much as a year--to allow sore feet to grow out and develop substance and strength. Some horses might never be able to deal with hard going if unshod, but they might be comfortable on more forgiving footing.
O'Grady expressed hope that more hi-tech shoes would become available in the near future, particularly shoes no thicker than a hacksaw blade yet made of material strong enough to insert a traction device as needed. The objective with such "shoes" would be to leave the frog available for contact with the ground to develop a better foot, while eliminating the weight and disadvantages of standard shoes.
Healthy Horses Workshop: Joint Disease and Lameness
"Traumatic joint disease is the leading cause of lameness in horses--and it can happen to any horse at any time," said James Casey, DVM, MS, who runs an equine sports medicine and dentistry practice in Laurel, Md. "More than half of all equine lameness is due to noninfectious joint disease and injury. It can happen from one bad step, but it's most likely due to cyclic (repeated) trauma."
Casey discussed joint disease and lameness for a full house of 303 horse owners at the 2006 Healthy Horses Workshop, held in conjunction with the American Association of Equine Practitioners 52nd annual convention on Dec. 2 in San Antonio, Texas. His main point: Prevent joint disease rather than treating it once it has occurred.
"You don't wait until your car is completely broken down to get it fixed; you usually get oil changes and maintenance before it gets to that point," he recommended. "Think of veterinary medicine the same way."
For the racehorses he primarily treats, "We usually go through and inject joints as a preventive treatment before and during the seasons," he said. "Not every horse needs that, but if they're doing maximum performance, it helps maintain health in the joints."
Progression of Joint Disease
Casey discussed the structural and fluid components of joints before moving on to joint disease.
"Joint disease is a process. It starts with a little problem, then it snowballs," he said. "A little synovitis gets worse and leads to pain, which leads to reduced use of the limb, muscle atrophy, unequal forces (loading), more pain, etc. Predisposing factors include poor conformation and joint instability. We cause a lot of these problems ourselves with poor breeding, shoeing, footing, etc."
Inflammation is a key part of the joint disease process, Casey explained--it's a normal body function that leads to repair and wound healing. Thus, it signifies injury. White blood cells play a big role in this process. However, when the stimulus for inflammation is too strong, the inflammatory process itself causes damage to joints.
Casey described the progression of joint disease as follows:
"First, there's synovitis--the synovial membranes (which line the joint and produce synovial fluid to lubricate it) become inflamed and permeable. Then white blood cells gain access into the synovial fluid, burst, and release enzymes that break down hyaluronic acid (HA, a gel that lubricates and cushions the joint) and destroy its lubricant/barrier function. Eventually, these enzymes gain access to the articular cartilage (covering the ends of bones' joint surfaces) and the surface of the cartilage starts to fray because it can't repair as fast as it's damaged. Once the articular cartilage is impaired, it can no longer provide equitable distribution of forces or compliance. The subchondral bone that lies directly underneath the protective cartilage now can't take shock forces, and you end up with bone fractures (joint chips, or maybe bigger fractures).
"Degenerative joint disease becomes a vicious cycle," he added. "When full- thickness loss of cartilage occurs, this is permanent."
Watch for the Signs
"Once you see something (joint pathology) on a radiograph, you're a long ways down the road with this problem," Casey cautioned. "We need to try to interrupt the process earlier. Notice subtle differences in the way the horse moves and how aggressively he trains. If you see a change, call your veterinarian. He/she can perform a physical exam and also may perform a synovial fluid analysis of the affected joints. The synovial fluid's thickness and consistency is an indication of a joint's health."
He also recommended that owners watch for the cardinal signs of inflammation around joints: heat, pain, swelling, redness, and loss of function.
"Digital radiographs, infrared thermography, and MRI (magnetic resonance imaging) can all help diagnose causes of a joint problem," he went on. "One thing to keep in mind is if you've got something wrong in one place, the horse is often sore in other places, too. If he's sore in a hind limb, he might be sore in his back (from carrying himself differently to compensate for the sore area)."
Treating Joint Disease
"There is no set treatment regimen for affected horses," Casey said. "You can go a long way by maintaining proper body weight for that horse, modifying his shoeing, and/or modifying his activity level. Some horses may benefit from a dose of Bute (phenylbutazone) before and after strenuous activity. And rest is always a part of treatment; it relieves use trauma and allows inflammation time to subside and damage to heal. Ask yourself: When it comes to treating your horse, do you just want to patch him up for the pain, or heal him?
"Unfortunately, rest by itself is not enough, so we might add physical therapy, cold hydrotherapy, acupuncture, ultrasonography, shock wave therapy, hyperbaric oxygen therapy, and/or surgery to remove fragments, stabilize intra-articular (within a joint) fragments, lavage (wash out) the joint, or employ therapeutic joint injections," he said.
The goals of treating traumatic and degenerative joint disease are as follows, he said:
1) Alleviate the immediate effects of inflammation, including pain and reduced function.
2) Prevent the development of permanent fibrosis in the joint capsule (as a result of uncorrected inflammation), which in turn can cause decreased shock absorption in the joints.
3) Prevent or minimize the development of osteoarthritis.
4) Normalize the inflamed joint(s) as quickly as possible before permanent damage occurs.
He also discussed the following medical options:
Corticosteroids are a good thing when used properly; they are the most powerful anti-inflammatory in our arsenal for joint disease. They work by stabilizing the membrane and keeping white blood cells out. There are several choices of medications; some are more potent or longer-acting than others.
Potential side effects include delayed healing and decreased resistance to infection. When corticosteroids are used properly, the benefits outweigh the risks, he noted.
Non-steroidal anti-inflammatory drugs (NSAIDs) include phenylbutazone (Bute) and flunixin meglumine (Banamine). "I always give a little Bute or Banamine at the same time (when giving joint injections)," he commented. "And Surpass (diclofenac sodium, a topical NSAID) is good for certain things, but it doesn't go real deep."
Hyaluronic acid is anti-inflammatory; it inhibits a type of prostaglandin that affects joints, toxic oxygen radicals, and cell migration. It also lubricates the joint, helps restore the function of HA that has been lost due to inflammation, and improves endogenous (caused by factors inside the organisim) HA production. Use it for mild to moderate synovitis, and keep in mind that higher molecular weight is better.
Polysulfated glycosaminoglycan (PSGAG) is a small molecule that can actually infuse into the cartilage. It acts as a building block for healing joint disease. "It's referred to as a DMOAD (disease-modifying osteoarthritic drug)," Casey noted. "It inhibits enzymes from breaking cartilage and synovial fluid down further and stimulates both collagen synthesis and production of hyaluronic acid." PSGAG (Adequan) is available in two forms, intramuscular (IM) for systemic use and intra-articular for direct joint injections.
Interleukin-1 receptor antagonist protein (IRAP) blocks bad interleukin (a mediator of inflammation) and allows good interleukin to work. It's a non-pharmacological approach that uses the horse's own materials to help him heal. (See www.TheHorse.com/ViewArticle.aspx?ID=6619 for more information.)
TILDREN, or tiludronic acid is not approved for use in the United States, but your veterinarian can get permission to import this drug. It inhibits bone reabsorption. It has been effective for navicular syndrome and is similar to a drug women take to inhibit osteoporosis.
"The main thing I want you to take away from here is this: Don't let a horse break down before you fix him," said Casey. "Work on him in between times, keep him shod properly, maybe use joint injections as needed. Treat him like your car, take him in for maintenance." It might cost money to inject his joints, he said, but that's a lot cheaper than surgery later or not being able to use the horse.
The "Joint Disease and Lameness in Horses" PowerPoint presentation shown at the Healthy Horses Workshop may be viewed on Casey's Web site: www.equinehorsevet.com/jmc-faqs.htm (12.9 MB).
About the Author
POLL: University Equine Hospitals