It wasn’t all that long ago that a horse with joint problems basically had three options: turn out, long-term phenylbutazone or corticosteroid injection into the joint. Nowadays, anyone who insists those are still your only options is living in the dark ages.
Over the last decade, we’ve seen a rise in viable herbal alternatives to bute, like devil’s claw, as well as a wide variety of therapy devices, like magnets, that keep our horses moving comfortably. And, of course, joint nutraceuticals have proven their value so substantially that they are now nearly a feed-room basic in most high-performance stables.
Depending on the degree of your horse’s problem, however, your veterinarian may recommend a stronger approach. You’ll be told about intravenous or intra-articular (in the joint) hyaluronic acid and hear about brand names like Hylartin V or Legend. He or she may also mention intramuscular Adequan or simply suggest high-dose joint nutraceuticals. Deciding which is best for your horse can be confusing, and none of these products is inexpensive. Knowing the advantages and disadvantages of each can save you a lot of headaches.
Hyaluronate, aka “acid”
Hyaluronic acid (HA) joint injection began as black-market use of European and Canadian products in racehorses in the late ’70s. Word about its excellent response rate spread rapidly across equestrian disciplines. By 1984, the first FDA-approved product for HA joint injection was available, Hylartin V (Pharmacia & Upjohn Co.).
The early ’90s saw the introduction of the first — and still only — HA prescription drug for intravenous use, Legend (Bayer Animal Health), which obviously eliminated the risks of actual joint injection.
HA is a natural, important component of joint fluid and cartilage. Most people think HA primarily works by lubricating the joint surfaces, however, the direct lubricant effect only lasts a few days (half life in normal joints is 96 hours), even less in inflamed joints.
Most experts agree that HA’s greatest benefit is in blocking further influx of either inflammatory chemicals or white cells into the joint. It also may interfere with how inflammatory chemicals interact with each other, essentially breaking the chain of events in inflammation. In addition, HA may stimulate the natural production of high molecular weight HA by the synovial membrane.
The cost of HA products for joint injection varies according to the product’s molecular weight, with the heaviest being the most expensive. Arthritic and inflamed joints show a decrease in both the concentration and molecular weight of HA in the joint fluid. But, whether heavier is better when injecting is debatable.
Studies show that low molecular weight HA lubricated just as well as high-weight and that the molecular weight makes no difference in how well it prevents inflammation-caused blocks in the building of cartilage. However, clinical trials show — and most veterinarians would agree based on their own experience — that high molecular weight HA produces a better pain-relieving effect, making it our recommendation.
The data submitted to the FDA on HA efficacy showed fair-to-excellent relief of symptoms overall in joint inflammation purposely created for scientific study, as well as naturally occurring cases, in over 90% of horses treated with intravenous or intra-articular HA. Intra-articular HA effects usually last 30 to 35 days.
These days, the intravenous injection route with Legend is far more popular. Researchers surgically created knee chips on horses in order to follow horses treated with Legend after surgery and those not treated. The Legend horses showed obvious benefit. Treatment began on day 13 after surgery, continuing weekly for three treatments. Values were comparable to a normal joint, and treated horses experienced less lameness.
Adequan (Luitpold Pharmaceuticals) also came on the scene in the ’90s, as the FDA approved polysulfated glycosaminoglycans, or PSGAG, for joints. First used only for intra-articular injection, Adequan is now mainly used intramuscularly.
Glycosaminoglycans are natural components of joint cartilage, but the form in Adequan is polysulfated, meaning it has extra sulfur molecules. Exactly how PSGAG benefits joints isn’t clear, but studies submitted to the FDA show that the drug reaches joints in increased concentrations after intramuscular injection and that HA levels in the joint increase.
In clinical trials, improvement at the end of a seven-injection series of intramuscular Adequan, with injections every four days for 28 days, was rated as excellent in 36.8% to 40.5% of the cases. Additional studies using live animals have also shown improvement when using intramuscular PSGAGs.
However, in several experimentally induced cases of joint defects, intramuscular PSGAGs basically showed little-to-no effect on healing or was even considered detrimental to healing, depending upon the animal’s induced defect.
The Vet’s Eye View
In researching this article, we reviewed the treatment records for 22 of our field horses that were in active race training and contacted veterinarians whose practices involve primarily high-performance horses.
All the horses had been treated at one time or another with Legend, Adequan or a intra-articular HA. Of these, 19 were tried on at least two of these options.
We’ve found that HA was superior to PSGAG in reducing symptoms of inflammation and pain. Intra-articular injection was preferred for either severely inflamed joints or those that had not responded fully to intravenous HA. However, intravenous HA was preferred for early cases of synovitis/joint inflammation, especially because it enabled treatment of all the joints with a single IV injection.
Time to a positive clinical response after an intra-articular injection of HA averaged two to four days, compared to four days to two weeks with intravenous HA and three to four weeks with intramuscular PSGAG.
For low-grade problems and preventative purposes, we would start with joint nutraceutical supplements. At $1 a day or less, this is definitely the least expensive option and, for most horses, it’s also all they need to remain comfortable.
To quickly get on top of an acute, obviously inflammatory problem or flare-up of an old one, we found oral hyaluronic acid (Conquer) shows considerable promise as being as effective as intravenous HA (Legend).
At about $120 for a 30-day course, Conquer is also less expensive than Legend, which will cost a minimum of $75 per injection (plus farm calls, vet fee) and often requires a two- to three-shot series, a week apart.
The response to intramuscular Adequan is slower and, in high performance horses at least, hyaluronic acid seems to give better results. At $45 to $55 per injection (plus vet costs), with injections needed every four days for seven injections in a full course of treatment — and no evidence to suggest it’s superior to HA — it’s hard to justify the expense associated with Adequan.
Severely inflamed/damaged joints that are unresponsive to these therapies are candidates for a joint injection of HA. A combined approach of initial control using intra-articular HA and maintenance on joint nutraceuticals will often greatly lengthen the intervals between joint injections.
Also With This Article
Click here to view ”Preventative Injections: Save Your Money!”
Click here to view ”Keep ’Em Going.”
Click here to view ”Research References and Treatment Options.”
Click here to view ”Joint-Injection Risks.”
Click here to view ”Conquer Is Impressive.”