No one believes anymore that grain and hay alone can supply horses with all necessary nutrients. Our knowledge of nutrition has improved, and each dietary supplement on the market wears a label that screams some previously unknown vital role in equine health. But the biggest reason riders supplement their horses' diets is to get bigger, better performances.

Joint supplements are the perfect example. Horses can't perform to any level if their joints aren't functioning. When riders browse the product shelves for that ideal joint supplement, questions invariably arise. What's in the product? How does it work? Will it work for my horse? But before these questions can be answered, it is important to understand how a healthy joint works and what can go wrong.

Healthy Joints
Think of the joint itself sitting inside a balloon called the joint capsule. At the very center of the balloon is the most important part—the cartilage. Called "articular cartilage" because it sits at the exact point where the joint moves, or articulates, it covers the very ends of the bones in the joint. The articular cartilage of each side of the joint meet and slide against each other as the joint moves. The smooth, slippery surfaces of the cartilage allows the joint to move easily and with no pain to the horse.

Articular cartilage is built like a sponge. Long fibers of collagen comprise most of this sponge-like material. Long molecular chains that form the fibers can be made up of amino acids and sugars. Amino acids are best known as the building blocks of proteins, and glucose is probably the best known sugar. In cartilage, amino acids and sugars come together to form glycosaminoglycans. This is just a big word for a group of molecules that contain mostly sugars with some amino acids thrown in. The important things to remember about glycosaminoglycans, are that glucosamine is used to build them; chondroitin sulfate and hyaluronic acid are important glycosaminoglycans; and glycosaminoglycans are attached around a protein core to create some of the long fibers of cartilage. To summarize, the body uses glucosamine to build chondroitin sulfate and hyaluronic acid (two important glycosaminoglycans) which attach to a protein core to form some of the cartilage fibers.

These particular fibers are not the only ones present in articular cartilage, but they do play a key role in how much water fills the "sponge" of cartilage. Without the interaction of chondroitin sulfate with the surrounding collagen fibers, the spongy cartilage absorbs too much water and does not function correctly.

In the midst of the cartilage matrix of fibers are cells called chondrocytes. Chondrocytes are the generating plant of the cartilage, responsible for building the matrix of fibers. Chondrocytes take sugars and amino acids, for example, splice them together in the proper way, and spit them out to add to the matrix. As in all body tissues, a constant repairing is going on. Some parts of the cartilage matrix are being destroyed or worn away, and the chondrocytes are constantly replenishing what is lost.

These cells use other components to help build the material for the matrix. Components such as vitamin C (ascorbic acid) and manganese are considered cofactors. Cofactors play a role during the process of forming the matrix, but do not form the matrix themselves. Think of cofactors as the wood clamps you might use while building a chair. You use them during the process, but once the glue is set, the clamps are removed from the finished product. In a similar way, cofactors show up in the building process of glycosaminoglycans, but are removed before the process is completed. So now we know that chondrocytes build all the fibers in cartilage and use cofactors during the process.

Chondrocytes occupy only about 5 percent of the total volume of cartilage. The health of the matrix depends on these cells. At the same time, the cells depend on the strength of the matrix to protect them from the physical stress generated by the motion of the joint itself. In essence, chondrocytes are alive because they build the protective cartilage matrix around themselves.

Healthy cartilage is resilient. It will compress when the joint moves, yet spring back to its original shape. The strength and resilience of the cartilage, which is derived from the proper matrix fibers created by chondrocytes, is just as important to the function of the joint, as the smooth and slippery characteristics. The strength protects the bone (and the chondrocytes), the smoothness ensures ease of motion. Healthy cartilage is all these things, but what it lacks is its own blood supply.

The articular cartilage sits at the center of the balloon we call the joint capsule both literally and figuratively. All other functions of the joint capsule involve maintaining healthy cartilage.

On the inner surface of the joint capsule "balloon" is the synovial membrane. This membrane secretes the synovial fluid which bathes the cartilage with a nutrient-rich mucous. The thick fluid acts as a lubricant, but it is also the main food supply for the chondrocytes in the cartilage. Exactly like wringing out a sponge in a bucket of water, the compressive action of the joint as it moves draws the fluid into the cartilage matrix, then squeezes it back out again. With each compression of the joint, chondrocytes absorb the nutrient building blocks they need to replenish the protective fiber matrix. The thin synovial membrane itself receives all nutrients from a series of blood vessels on its outer surface. To a much lesser degree, chondrocytes can get some nutrients from the rich blood supply to the bone itself lying underneath the cartilage.

Outside the synovial sac is the final layer in the joint capsule. This layer contains the ligaments and tendons responsible for keeping the joint stable and moving in an even, straight motion. Small fluid-filled sacs called bursae, lubricate and protect the tendons and ligaments from injury.

When Joints Go Wrong
Joints are built to be tough, but they aren't indestructible. It's dependency on all the surrounding tissues and fluid means that articular cartilage can be indirectly affected by any injury to the joint capsule. Injuries to the tendons or ligaments can create uneven wearing of the cartilage while the injury heals. Damage to the synovial membrane affects the nutrients and lubricating properties of the fluid supporting the cartilage. Exercise, both too much or too little, can also cause negative changes in the quality of the cartilage.

Osteoarthritis often develops from an injury to a joint. This disease is painful and may involve inflammation around the site of the injury. In osteoarthritis, the cartilage wears away over time, and pain increases as the bone ends, unprotected by cartilage, rub together. As more of the bone is exposed, the surface of the bone itself changes, forming bone spurs or excess calcification at the site.

In early stages two things can happen at or around the joint. Tiny fissures in the cartilage can grow larger and pieces of the cartilage can actually break away. And, as happens with every injury, the body responds with inflammation. Inflammation, a normal response, can easily get out of control.

Inflammation causes an increase in watery fluid to the site of the injury. Either because the site is not allowed to fully heal and is reinjured, or because the body's inflammatory response has gone haywire, there is a continual presence of too much fluid. If this response goes on for too long, chondrocytes are triggered to release enzymes which attack the long fibers in the cartilage. These enzymes attack the cartilage matrix, and a percentage of glycosaminoglycans, such as chondroitin sulfate are lost. Their loss, as mentioned above, allows an increased amount of water into the cartilage matrix. A viscous circle of degradation starts, as first the cartilage, and then the chondrocytes are lost to some extent. Cartilage is being destroyed faster than the surviving chondrocytes can replenish it. Reducing inflammation helps reduce pain, but does not address the real issue of cartilage degradation.

Treatment
Comprehending the issues involved in joint injuries and joint disease, makes obvious that several factors should be treated simultaneously.

Exercise should be adjusted to promote proper healing and reduce further damage. Dr. Christopher Kawcak of Colorado State University's Equine Orthopaedic Research Laboratory supports a global approach to joint disease.

"In my opinion," Kawcak says, "the health of articular cartilage depends on proper conditioning. While severe injuries can require stall rest, in most cases, exercise, in the form of simple hand walking or trail riding, may benefit diseased joints and tissues." Stall rest as a treatment is needed in severe cases of musculoskeletal injury, but some form of exercise, even simple hand walking or trail riding, may be beneficial to diseased joints and tissues."

Controlling inflammation has long been known as an important component in treating joint disease. Hyaluronic acid, a glycosaminoglycan mentioned above, has been used as an antiinflammatory. Chondroitin sulfate is considered to have mild antiinflammatory benefits. And coritcosteroids are well-known strong antiinflammatories.

"Most antiinflammatory medications," says Kawcak, "reduce inflammatory enzymes, decreasing their degradative effects on articular cartilage."

Another component of treatment which is quickly gaining general acceptance, is supplying the building blocks of cartilage to the joint so that the cartilage will regenerate, or at least stop degrading. The theory supporting joint supplements says that if cartilage building blocks are supplied in excess of what is needed, the cartilage will at least maintain or possibly even rebuild itself. This theory is not completely accepted in the equine scientific community, mainly because there is no real data to prove the theory correct. In spite of this somewhat controversial theory, there is hope that joint supplements can work.

Dr. C. Wayne McIlwraith, also of Colorado State University, is considered to be on the cutting edge of equine orthopedics research. "Based on personal experience and through conversations I've had with other veterinarians," he says, "I believe these joint supplements are of benefit."

Dr. McIlwraith "believes" the supplements are of benefit because, like all researchers, he'd rather have proof.

Can Joint Supplements Work?
"It is still necessary," says McIlwraith, "for a supplement manufacturer to 'step up to the plate' and finance a study in live horses that will prove their claims."

Joint supplements are considered "nutraceuticals" and are not regulated by the Food and Drug Administration. Manufacturers are not required by law to produce scientific data that prove their products work.

Nick Hartog, President of the National Association for Equine Supplement Manufacturers, says many manufacturers are sympathetic to the criticism. "Scientific studies are very costly," he says, "and most manufacturers simply can't afford them, particularly given the fact that manufacturers can not patent nutritional products effectively, and thereby protect their investment. At the same time, these companies believe the studies are a necessary next step."

Looking at the ingredients of the joint supplements on the market, the combinations make sense.

"Loss of glycosaminoglycans is an early event in osteoarthritis," says McIlwraith, "and therefore chondroitin sulfate supplementation has a logical rationale. In addition, there is evidence that chondroitin sulfate inhibits degradative enzymes that break down the cartilage matrix."

"Our company's informal studies have shown a positive effect," says Hartog, "and many consumers have reported results that indicate joint supplements do benefit their horses. The widespread use of oral nutraceutical products by veterinarians also gives support to the idea that there are measurable results."

The controversy remains whether supplements show real, scientific proof of improvement in horses. Studies in humans have already proven the benefit of these supplements. But can the results from human studies correlate directly to the same results in horses?

Absorption of joint supplements has been an issue for years. Oral supplements must first survive the digestive process and enter the bloodstream. Then the supplement must pass through the synovial membrane into the synovial fluid.

"Based on the scientific evidence available on absorption," says McIlwraith, "if one had a choice of using either glucosamine or chondroitin sulfate, I would choose glucosamine. Using an oral preparation that has both present is logical, but again, there has been no comparative studies done in the horse to demonstrate differences."

Injecting supplements is one way of getting around the absorption problem. Injecting glycosaminoglycans directly into the muscle (intramuscularly) gets the supplement into the bloodstream. Injecting them into the joint (intraarticularly) surpasses the synovial membrane barrier and gets them directly into the synovial fluid. Intraarticular injections are effective and nearly all vets will agree this method can diminish lameness. Hyaluronic acid is a logical choice because it not only is an important building block of articular cartilage, but it also has antiinflammatory properties. Hyaluronic acid, while not as strong an antiinflammatory as corticosteroids, nearly eliminates the negative side-effects common to repeated steroid injections.

For horseowners, injections may not always be feasible. Cost is a factor, not only of the medication but also of the veterinary fees associated with the injection. Some owners are uncomfortable with the risk of infection to the joint. And, as with any injection, the level of medication will decrease over time, likely making additional injections necessary.

"Oral supplements have their place," says Hartog, "ideally as a preventative regimen to keep levels constant and as a possible alternative or adjunct to the reactive and invasive treatment constituted by injections."

Many horseowners, seeing results in their own or others' horses, have chosen to add joint supplements to their horses' diets on a continuing basis. The best thing for them to know is that there are no known negative side effects. At this point in time, it is believed these supplements won't hurt horses. For owners who are already convinced, it may be more important to know how to choose the right supplement.

"There are a lot of brands on the market today," says Hartog. "The best advice I can give is to read the label. It should be easy to understand and include a complete list of ingredients and amounts of each delivered in every serving. If a horseowner cannot understand what they would be feeding their horse in the store before purchasing a product, that should represent a red flag. In addition, unrealistic time frames for results need to be recognized. Ask your vet if joint problems can be fixed in a matter of days. The adage 'if it sounds too good to be true it isn't' would definitely apply here .We are particularly concerned about consumers who are sold on hype – when buying a supplement pretend you are buying a used car—kick the tires a bit. Ideally, a lot number and expiration date should also be displayed."

A complete ingredient list should show horseowners if there are hidden antiinflammatories or if beneficial cofactors, such as manganese or vitamin C, are present. But owners need to better educate themselves about what these ingredients might be. Asking a veterinarian is necessary if an ingredient listed is unfamiliar. And don't be surprised if most supplements on the shelves at your barn don't list ingredients at all.

The lack of concrete scientific data in horses won't affect the supplement market. Consumers have accepted them. But data will allow vets to be more definitive in their recommendations.

"Because no company producing any oral nutraceutical product for horses has been prepared to invest in a controlled scientific study," says Dr. McIlwraith, "at the moment it is left up to the individual horse owner or equine veterinarian to do their own research on their own horses."