Sorry to hear about your new guy and his problems! 
We've had a couple of horses injected at the farm with a varying degree of success, and others on liquid and powder suppliments (MSM and Glucosamine). I don't know exactly how well they've done or what was injected since they weren't my horses so I can't help you with that but I did read the following article that was very intersting in my "Perfect Horse" magazine.
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John Lyons Perfect Horse December 2007/January 2008 issue: Joint Supplements Demystified
-by Eleanor Kellon, VMD
Joint supplements work. What's heartening is we finally have some formal studies in horses that back this claim up. However, if you tried several different supplements, you've probably found that some work better than others in helping your horse move more comfortably or controlling heat and swelling. One reason for this is the variable quality of the ingredients. Another is that some supplements may not contain what they claim to contain. Also, individual horses with similar conditions may respond differently to the same products and doses. Some may show marked improvement, while other show little apparent
There are so many formulas and acronyms, it's no wonder you're confused.
Here are the most common ingredients you'll find in joint nutraceuticals and why they're in there.
The same problem exists for human arthritis supplements. "Nutraceuticals," as these compounds are referred to, are not tightly regulated by the FDA, so "consumer beware" applies. It's easy to get lost among all the products, since there are around 75 different brands on the market, with many manufacturers offering several to choose from. What's more, new ingredients keep popping up.
Equine joint supplements that have been on the market for a long time are probably reasonably effective. However, the best approach is to start by reading labels to make sure the product you are considering contains appropriate ingredients in the correct amount.
<picture in magazine with following caption> "Heat, pain, and swelling are signs that a joint is under stress. Scientific studies are now supporting what many owners already knew-that nutritional supplements can alleviate pain and may help prevent further joint damage.
Recipes for Relief
- Glucosamine and chondroitin seem to work better together than separately.
- Combination products work best when they contain the recommended therapeutic dose of each ingredient.
- Oral hyaluronic acid (HA) may help during flare-ups to reduce heat and swelling.
- MSM is an effective anti-inflammatory when fed at a dose of 20,000 mg/day.
- Vitamin C is important for joint health, but too much supplemental C can be harmful.
- There is no "arthritis mineral," although copper and zinc are important antioxidants.
Glucosamine
Glucosamine is the most well studied ingredient in joint supplements. It comes as either glucosamine sulfate or glucosamine hydrochloride. Both are effective. Glucosamine is the basic building block of all connective tissues, including cartilage, in all forms of life. Glucoasime is usually either manufactured in a pure form or isolated from sources high in glucosamine, like the outer coverings of shellfish. Some products may contain "natural sources> of glucosamine, such as the sternum or trachea (windpipe) from cattle or hydrolyzed collagen from other sources (skin, tendon, ligaments). Hydrolyzed collagen will be mentioned below, but when shopping for glucosamine, it's best to stick with either the manufactured pure glucosamine or shellfish sources.
Glucosamine is effective in relieving pain, sometimes in as short a time as 10 to 14 days. Studies have shown that it can slow cartilage breakdown and may encourage healing. An effective dose is 6,000 to 10,000 mg/day. The 10,000 mg dose is usually needed for horses that are being worked. This higher level is also recommended during the first week or two of any horse's treatment, known as the "loading" period, which helps speed up results by getting a therapeutic level of the substance into the horse's system.
Chondroitin
Chondroitin sulfate is major structural component of cartilage, bone, and tough connective tissues such as the whites of the eyes. The pain-relieving effects of chondroitin are not as obvious as with glucosamin, although some observers report that horses on chondoitin only seem to move more "fluidly" overall. Formal studies on chondoitin give mixed results, with its greatest benefit appearing to be prevention of further cartilage breakdown. An effective dose is between 1,250 and 5,000 mg/day.
Glucosamine + Chondoitin
The most recent research is showing superior results for combinations of glucosamine and chondroitin, as contrasted to results when either substance is used alone. Many equine joint supplements now combine these two ingredients (among other things). What you will often find, though, is that a product may contain both ingredients, but the dosage of one, or both, is low compared to the individual dosages listed above. Products may claim - or imply - that when the ingredients are combined, you can lower the doses and get the same effect. But this has never been studied or documented. Some, but far from all, of these lower-dose products actually do work, but there are no formal, long-term equine studies to show us what's going on in the horse's joints. For the moment, your best bet is to use a combination product that supplies a full dose of glucosamine (for pain control) and as close to a correct dose of chondroitin as you can find.
Keep in mind that glucosamine and chondroitin are the cornerstones of any joint supplement program. Unless new research eventually shows something else works better, you should focus on those two. However, anything you pick up is likely to have a much longer list of ingredients.
So what about the other stuff?
Hyaluronic Acid
Glucosamin and chondroitin were being used in human arthritis patients before those ingredients spilled over to use with horse, but equine medicine has always had the jump on human medicine when it comes to hyaluronic acid. It is an important component of both the cartilage itself and the joint fluid. Hyaluronic acid first appeared as an injectable drug in the 1970s. (It was actually on the black market from Europe and Canada for a few years before FDA approved its use in American products.) Most recently, hyaluronic acid has been available as an oral supplement. Hyaluronic acid is particularly good for controlling pain, heat, and swelling. The gel formulations cost more, but seem to give the most rapid and reliable results. Dosage is 100 mg/day.
Hyaluronic acid is also found in a variety of powdered supplements. Addition of as little as 20 mg of hyaluronic acid (also know as "hyaluronate") to glucosamine and chondroitin combination product may make a difference for some horses. In other cases, you will have to use the full 100 mg dose if even more. If your horse has not responded as well to glucosamine and chondroitin as you had hoped, this is a reasonable next step. You can get an idea of how your horse may respond by first trying a gel in addition to your regular supplement for a few days.
Avocado and Soy Unsaponifiables (ASU)
Avocado and soy unsaponifiables are plant fats that are normally protected from digestion and absorption in the intestinal tract but are extracted and purified by a special procedure. In an equine study where arthritis was induced by a surgical procedure, these substances showed a protective effect against cartilage breakdown in a group of supplemented horses compared to those not supplemented. However, they did not appear to have an effect on pain. Yet studies in other species have shown that the release of inflammatory substances is inhibited, while growth factors needed for repair and maintenance increase. ASU is classified as a "chondoprotective" (chondro = cartilage). It is a slow-acting substance. You won't see results overnight. How ASU compares to glucosamine and chondroitin, and whether adding it to a standard combination-type supplement improves the effect, is currently unknown. Effective equine dose is at least 1,200 mg/day.
Methylsulfonylmethane (MSM)
Although it is still not clear how methylsulfonylmethane (MSM) works, or what the long-term side effects might be, it is an effective anti-inflammatory. One equine study in horses with hock arthritis showed it takes a dose of at least 20,000 mg/day to be effective. MSM is added to many joint supplements but rarely in doses that high. To assess your horse's response to MSM, buy a pure MSM product and add that at varying doses.
Hydrolzed Collagen
Collagen is a protein that forms the structural framework for all connective tissues in the body, including bone and cartilage. Hydrolyzed collagen is collagen that has been purified and also broken down into smaller protein units for easier digestion and absorption. It has naturally occurring amounts of glucosamin, chondroitin, and hyaluronic acid, but the benefit is believed to come from the connective tissue-specific protein and amino acids. Collagen hydrolysates have been used to promote wound and ulcer healing, and most recently, as a treatment for arthritis. Data is scanty to date, with no equine studies, but there my be an improvement in pain and joint function. However, the dosages required to get this effect in people have been quite high, and a horse may need as much as 40,000 mg a day. There is no information available on combinations of hydrolyzed collagen and other joint supplement ingredients.
Cetylated Fatty Acids (cetyl myristoleate, or CMO)
First discovered as a substance produced in a strain of mice that were remarkably resistant to arthritis, CMO (sometimes marketed under the name Celadrin) has received mixed reviews. It may help with pain and protect cartilage in some cases. It works better when combined with therapeutic dosages of other joint support nutrients, but no studies have been done to compare the combination of CMO with glucosamine/chondroitin versus just the glucosamine and chondroitin alone. Minimum equine dose is likely to be at least 1,400 mg but there are no formal equine studies.
Vitamin C
Vitamin C is essential for the health of cartilage and other connective tissues, but this is definitely an area where more is not better. Excessive amounts may even damage cartilage. No equine studies are available. The equine equivalent of a human dose found to have a mild effect would be 4,000 mg/day, but a horse's body is capable of manufacturing its own vitamin C, and this could be too high. A horse on fresh pasture is taking in about 1,000 to 2,000 mg/day of vitamin C from grass.
Herbs
A variety of anti-inflammatory herbs are often added to equine joint supplements, but "it's in there" is no guarantee the amount being added is enough to have any effect. These herbs are most useful for horses that continue to have pain despite adequate doses of other joint nutraceuticals. The list of herbs is a long one, but here are some of the most commonly used and their likely effective dosages:
- Devil’s Claw – 2,500 mg of a standardized 0.25% harpagoside extract
- Yucca – 3,000 mg/day of 10% saponin powder to 15,000 mg/day of 2% saponin powder
- Boswellia – 500 mg/day of extract
Manganese Manganese is a trace mineral (meaning that it’s needed in very small amounts) that plays a critical role in cartilage metabolism. Manganese is required for the production of chondroitin sulfate in the body. However, if your horse’s hay, pasture, and grain are like the vast majority, he is not only meeting his minimum requirements but probably getting a lot more manganese than he needs. There are no studies, in any species, connecting manganese deficiency to arthritis or showing a benefit for supplementing manganese. With minerals, more is definitely not better. Avoid manganese entirely or find the lowest dose you can (25 mg or less) while still getting the other ingredients you’re after. Copper and Sulfate These minerals aren’t included as commonly, but since we just talked about manganese, this is a good place to discuss them. Many equine diets are both high in manganese and low to downright deficient in copper and zinc. Copper plays a key role in connective tissue formation, and both copper and zinc are involved in one of the body’s important antioxidant enzyme systems. Long story short, your horse’s mineral supplements really should be based on his overall diet. There is no “arthritis mineral.” Copper and zinc are commonly deficient in the equine diet, so it makes more sense to supplement them than manganese. But there’s no guarantee that the amounts in a supplement will be appropriate for your horse’s diet. If they are in the supplement, 50 mg of cooper and 150 mg of zinc are reasonable and safe potshot levels. Summing Up· Don’t wait until your horse is severely lame to start a joint supplement. Some changes may be irreversible.· Start with a supplement that provides 6,000 to 10,000 milligrams (mg) glucosamine and 1,250 to 5,000 mg chondroitin. · Hyaluronic acid is most useful for acute flare-ups or for horses with persistent heat and swelling, which indicates ongoing inflammation.· Avocado and soy unsaponifiables (ASU) and cetylated fatty acids (CMOs/Celadrin) are both slow-acting ingredients that may protect against further cartilage breakdown. Don’t Wait. . . until your horse is severely lame to start a joint supplement.Although cartilage can repair itself to some extent, once breakdown starts, it is difficult to get on top of it enough to push the balance in favor of healing. Once cartilage is severely thinned or completely work through, the damage may be irreversible. Uncontrolled arthritis can also lead to the buildup of bone/calcium around the joint, which limits movement and is also irreversible. Horses that have not progressed this far will have a better response to joint supplements. No Response? You May Need to ExperimentWhat about nonresponders?
Joint supplement aren’t magic wands that will instantly transform an arthritic horse, but they do help most horses. If yours doesn’t respond to a supplement with correct dosage