JOINT PROTECTIVE AGENTS

by Jennell Appel, DVM, CCRT

         In this day and age, it is extremely easy to become overwhelmed with the seemingly endless products available on the market labeled for joint health and protection. Walk into any local pharmacy or health food store, and it becomes clear that you could spend nearly half of a day reading labels, yet walk away even more confused than when you arrived. The goal of this article is to provide you with an understanding of where these agents are derived from, how they function in the body, and the benefits of administration to our retrievers. I will also discuss several of the products that I personally recommend for my retriever patients.

        Articular cartilage is found in all movable joints of the body. Not only is it responsible for protecting bone from repetitive stress and wear, it is also composed of cells called “chondrocytes,” which actively secrete molecules that replace degraded proteins and metabolites within the joint. Damage to these cells can occur quite easily and in many different ways. A traumatic injury such as cruciate ligament tear, is one of the leading causes of acute cartilage damage in our canine athletes, but chronic changes can be seen even without injury. The daily stress and wear and tear that athlete joints endure, is enough to set the stage for osteoarthritis.

        Injury or excessive trauma may both result in joint inflammation. The cascade of events eventually leads to invasion of the joint by white blood cells. These cells release destructive enzymes, which ultimately affect the viscosity of joint fluid, in turn, decreasing mobility and causing pain.

        All of the joint protective agents listed below have three primary functions in common:

1.       Support and enhance the metabolism of chondrocytes (cartilage cells) and synoviocytes (cells responsible for producing joint fluid).

2.       Inhibit degradative enzymes in the joint fluid and within cartilage.

3.       Inhibit formation of thrombi (small blood clots) within the blood vessels supplying the joint.

Glucosamine

        Glucosamine is a component of Glycosaminoglycans (GAG). This is simply a fancy word for long chains of a sugar molecule. An example of a GAG is Hylauronic acid, which is found within joint fluid, and plays a critical role in maintaining the integrity of the joint capsule itself. Glucosamine supplementation is used to stimulate the synthesis of GAGs, thus aiding the joint in Hylauronic acid production. Although oral absorption of Glucosamine has been brought into question by many physicians in the past, it has been proven that in dogs, 87% of oral Glucosamine is absorbed within 2 hours following administration. My current dosing recommendation is at least 600mg daily.

Chondroitin Sulfate

        Chondroitin is the predominant GAG found in cartilage, making it one of the most critical components of collagen synthesis. When given orally, Chondroitin has 100% bioavailability and has been proven through several animal models to decrease cartilage degeneration by blocking histamine-mediated inflammation. There have also been multiple in vivo studies evaluating the efficacy of glucosamine/chondroitin combination therapy. Canapp et al reported that this combination has significant anti-inflammatory effect against chemically induced synovitis in dogs. My current dosing recommendation is at least 250mg daily.

Methylsulfonylmethane (MSM)

        MSM is a metabolite of DMSO, which functions in the body as a free radical scavenger. It is believed to be a natural anti-inflammatory, however, the biochemical effects are still poorly understood. Several human studies have been published, evaluating MSM supplementation and the pain associated with knee osteoarthritis, yielding positive results. Further investigation through both human and animal trials are currently underway.

Avocado/Soybean Unsaponifiables (ASU)

        ASU’s are natural vegetable extracts made from avocado and soybean oils. They have been shown in cell studies to not only protect cartilage, but to enhance the inhibition of cartilage breakdown when paired with Glucosamine and Chondroitin. One recent study performed by Nutramaxx Animal Laboratories evaluated the joint fluid two groups of dogs. One group was administered a daily dose of 300mg ASU, the other a placebo. The ASU treated group was found to have an increase in TGF-beta 1 and 2, which are proteins responsible for counteracting cartilage breakdown. My current dosing recommendation is at least 45mg daily.

Omega-3 Fatty Acids

        The protective health benefits of Omega-3 supplementation have long been documented in human medicine, but only recently have studies begun to shed light on how important they are for our canines as well. There are several forms of Omega-3s, but DHA and EPA are those that are most beneficial for the body. In a study performed by Hill’s Science Diet, one group of osteoarthritic dogs was fed a diet with no Omega-3s, while the other was fed a diet rich in Omega-3s.  Following a 6 month trial, lameness scores revealed significant improvement in stiffness and mobility in the group receiving Omega-3 supplementation. A decrease in the level of inflammatory cells and degradative enzymes within the joint was also observed.

        The most important factor when deciding upon which Omega-3 formulation to administer is the source. Proper processing is essential for product purity as well as efficacy. Following months of my own personal research, I currently recommend Nordic Naturals Omega3 Pet for all of my patients. This product is currently backed by 14 scientific journal clinical trials, with at least 30 more underway. They also use natural enzymes to produce highly concentrated products, which are manufactured in triglyceride form, ensuring 100% absorption and bioavailability. Nordic Naturals products are third-party tested for environmental toxins including heavy metals, dioxins, and PCBs, ensuring that every product exceeds international pharmaceutical standards and is at least 750 times purer than fish. Nordic Naturals was ranked #1 out of the top 10 fish oil companies in Norway for freshness, purity, and highest concentration. My current dosage recommendation for most patients is 3000mg once daily. Dogs with osteoarthritis or a history of joint injury may take upwards of 6000mg daily.  

Veterinary Products

Polysulfated Glycosaminoglycan (Adequan)

        Adequan is an injectable veterinary formulation derived from bovine trachea. It functions in the joint by binding to damaged cartilage, stimulating repair processes, and suppressing degradative enzymes. Adequan eases joint movement by providing lubrication, and thus, decreases pain. The Canine formulation of Adequan is the only FDA-approved product of its kind. Current dosing recommendations include twice weekly intramuscular injections for 4 weeks, followed by a once monthly maintenance injection. The injection is absorbed within 2 hours of administration and stays active within the joint for 3 days. The only known negative side effect of Adequan is mild blood thinning within the first 24 hours post-injection. Therefore, any dog known or suspected to have a clotting disorder, such as Von Willebrand disease, are not candidates for treatment. Due to its proven protective benefits both in equine and canine veterinary medicine, I personally recommend one intramuscular injection every 2 weeks following the induction course for retrievers in active training/competition.

Hylauronic Acid

        Hyaluronan (HA) is one of the major molecular components of joint fluid. Its high viscosity provides essential lubrication to cartilage surfaces, allowing for smooth, unrestricted joint movement. HA joint injection therapy is based upon the physiologic importance of the role of Hyaluronan in the joint. The therapeutic benefits include restoring viscosity, lubrication, and elasticity within the joint, thereby decreasing pain. Many of the canine studies evaluating HA have been performed in dogs following cranial cruciate ligament transection. Results showed positive responses, with decreased severity of osteoarthritis microscopically, and restoration of viscosity with a direct cartilage protective effect. No adverse systemic side effects have been observed. HA is available in an oral form as well, but currently there are no studies supporting the efficacy of this formulation.

        I have utilized this treatment in dogs with conditions ranging from severe osteoarthritis to partial cruciate tears and have been impressed with the results. Decreased pain, increased mobility, and significant improvement in degree of weight bearing are several of the positive benefits I have observed in my patients. My current treatment protocol consists of once weekly injections for a series of 3 weeks. Typically, the benefits of this treatment are observed up to 8 months following the last injection.

Dasuquin

        Dasuquin is a joint supplement containing Glucosamine, Chondroitin, ASU, and MSM. This product is formulated for dogs and contains human grade ingredients in terms of quality and purity. A recent study evaluating the efficacy of this combination in dogs found that adding ASU to Glucosamine and Chondroitin had even greater effect at decreasing inflammatory mediators within the joint than just Glucosamine/Chondroitin alone. In my personal experience, I have observed a dramatic difference in mobility and comfort level in my osteoarthritic patients since I began prescribing this product, which one of the reasons I now recommend it to all of my clients. For my canine athletes, I begin every other day administration at 12 weeks of age, with daily dosing starting at either 6 months or upon initial entrance into competition.

        The best use of glucosamine/chondroitin is that as a means of prevention, not treatment. This is why it is important to begin providing supplementation at a young age, before cartilage wear and/or damage occurs. Following injury or cartilage degradation, supplementation will aid in preventing further breakdown by decreasing inflammation.

        In conclusion, there are hundreds of joint protective agent products available, but two important factors to always take into consideration include clinical trial data and ingredient source. If there is no science to back up what the product is claiming, then they have no authority to claim it. If the manufacturer is unable to produce guaranteed analysis data regarding ingredient source, concentration, and purity, then you truly have no way of knowing what is in the bottle. Many of these products are used in humans as well as animals, but remember that not all are created equal. Absorption levels are critical for efficacy, and many times, these products require specific processing for optimal absorption in dogs. So, be sure to do your research, or ask a veterinarian who has done theirs!