Monday, February 8, 2010

Monday, Feb 8 2010 - Winding up the Hock

Vet Tip of the Day: Oral Joint Supplements
Key words: chondroprotectant, synovial fluid, cartilage, joint capsule

Osteoarthritis is only one of many conditions that affect the hock; in the future we will come back and discuss other disease processes that affect tarsal joints.  But to conclude this introduction to hock anatomy and bone spavin, the most common cause of hock lameness, there will be two final Vet Tips of the Day: today we will look at oral joint supplements, how they work, and IF they work.  Tomorrow we will consider injectables.

It is important to distinguish between oral and injectable agents administered as chondroprotectants.  "Chondro" refers to cartilage, "protectant" is self-explanatory.  Chondroprotectant joint supplements are substances which claim to enhance the health of joints by improving the the quality of joint fluid and joint cartilage.  Cartilage is the spongey substance which lines the surface of bones within joints.  The cartilage is bathed in synovial fluid, or joint fluid, which is contained within the joint space by the joint capsule.  The joint capsule is lined by synovium, the site of joint fluid production.  In the simplest terms, the joint fluid and cartilage act as shock absorbers to diminish the force transmitted to bones when joints are compressed by weight bearing.

You've almost certainly heard of glucosamine and chondroitin.  These are two of the most common ingredients in oral chondroprotective joint supplements.  These substances are two of the primary building blocks the body uses in the construction of cartilage.  Theoretically, by increasing the amount and quality of glucosamine and chondroitin in the diet, the body is better able to produce and maintain healthy cartilage.  There are three major problems with this theory.  First, there are many structural varieties of glucosamine and chondroitin, and their absorption across the gut wall is widely variable.  Second, and perhaps more importantly, there are few government regulations regarding the manufacture of oral joint supplements, which are considered "neutraceuticals".  Therefore, the amount and quality of ingredients listed on the label vary widely from product to product, and there is not even any guarantee that the label claims of a given product are true.  Therefore, when buying an oral joint supplement, you are completely at the mercy of the manufacturer's ethics regarding the actual contents of the product.

Finally, the third problem is, assuming the product you buy is excellent quality and your horse absorbs the ingredients, there is very limited research availabe indicating what an appropriate dosage is for a given combination of chondroprotective ingredients.  In addition to glucosamine and chondroitin, additional additives found in many joint supplements include cetyl myristoleate (an anti-inflammatory) , hyaluronic acid (a major components of joint fluid), as well as various herbal extracts such as devil's claw, boswellia and avocado extract, just to name a few.

Before you throw in the towel, be comforted in knowing that, while limited, there are a few well designed clinical studies indicating that the oral administration of chondroprotective agents can improve lameness in horses with chronic osteoarthritis.  The bottom line is, at this time there is more unknown than known about these products, so if you choose to give one to your horse, buy a recognized brand manufactured by a company with a longstanding reputation.  Be sure the product is clearly labelled with respect to ingredients, amounts of ingredients, and recommended dosage.  It should be easy to calculate the actual amount of each ingredient you will be giving your horse by reading the label.  The product should have a lot number and expiration date easily identifiable, and there should be clearly printed information telling you how to contact the manufacturer.  Finally, if the product claims to cure everything from laminitis to navicular disease to hock pain in 30 days, don't buy it.  Remember, you get what you pay for, and if it sounds too good to be true, it probably is.


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