Think of them as the silent sufferers: the millions of dogs who hobble among us, creaking away on swollen joints and dwindling cartilage. Most are older, but the years didn’t make them that way. Arthritis did.
Osteoarthritis is the biggest cause of chronic pain in U.S. dogs. According to most estimates, it affects more than 20 percent (that’s 10 to 12 million animals).
Technically speaking, osteoarthritis, or OA, is a degenerative disease involving one or more joints in a dog’s body. It most often shows up in middle-aged or older dogs, although there’s no standard age of onset, explains Jamie Gaynor, DVM, MS, director of the Animal Anesthesia and Pain Management Center in Colorado Springs, Colo.
But OA isn’t just an old dog’s disease, nor is every dog destined to be arthritic. OA is generally triggered by excessive wear in one or more joints, but dogs who have joint irregularities are more likely to develop arthritis in the affected joint. These irregularities can be caused by trauma—an accident or injury—or by a developmental deformity, such as hip or elbow dysplasia, which is a genetic condition that develops in a dog after birth.
Other factors that can contribute to OA are obesity (see sidebar) and overuse. This is a problem for racing dogs as well as for many working breeds; they may not be herding sheep or pointing at birds for a living, but many still feel compelled to run around as though they were.
Osteoarthritis is tough to manage, in part because it’s cyclical: Inflammation creates pain as well as physical changes that force the joint to move in an unnatural way, creating more pain and inflammation. Once it gets started, arthritis is difficult, if not impossible, to stop.
What’s more, just controlling the pain of arthritis is anything but simple. Researchers have found that arthritis pain follows several different pathways and creates changes in the dog’s central nervous system, which means that keeping an arthritic dog comfortable most often requires more than one type of pain relief.
There’s no cure for OA—treatment generally focuses on treating the discomfort and slowing the loss of cartilage and damage to the joints.And vets agree that there’s no silver bullet: No drug or therapy or supplement works on every dog, and no two dogs respond in exactly the same way to any treatment.
But there are steps that you can take to slow the progression of arthritis and keep your dog as happy and active as possible.
This last group, known as diseasemodifying agents, can create changes in the dog’s body that have a direct impact on the progression of a disease, explains Dawn Boothe, DVM, PhD, professor and director of the clinical pharmacology laboratory at Auburn University’s College of Veterinary Medicine in Auburn, Ala. In a dog with arthritis, these supplements can make the cartilage healthier and better able to fight off the damaging effects of OA.
The supplements listed here can be combined with other remedies, but check with your vet before adding them to your dog’s diet. Give any supplement at least four weeks to work, says Carvel G. Tiekert, DVM, executive director of the American Holistic Veterinary Medical Association.“If you don’t see any changes after six weeks,try something else,”he says. (For another cautionary note, see the final page.)
Glucosamine and Chondroitin Sulfate. These substances provide the building blocks for polysulfated glycosaminoglycans, or PSGAGs, which are long-chain molecules that hold water and give cartilage its cushion. Research shows they can be very effective in both animals and humans. A recent study (Grainne McCarthy, James O’Donovan, et al., published in The Veterinary Journal 2007; 174:54–61) found that arthritic dogs given a supplement of glucosamine and chondroitin for 10 weeks had significantly less pain than dogs who didn’t get the supplement.
However, not all glucosamine is created equal. “There’s a huge range in quality of these supplements,” says Dr. Boothe. To be sure you’re getting your money’s worth, stick with products that have been proven effective in studies. Both Dr. Gaynor and Dr. Boothe recommend products from NutraMax Labs, which manufactures Cosequin and Dasuquin. Glyco-Flex III, from Vetri- Science Labs, is also well researched, says Dr. Gaynor.
Avocado/Soybean Unsaponifiables (ASUs).
Perna canaliculus (Green-lipped Mussel).
Of these, the first four are COX inhibitors (they target the cyclooxygenase, or COX, enzymes responsible for inflammation and pain). “Some dogs respond better to one, but they all have essentially the same mechanism,” says Dennis Caywood, DVM, MS, a diplomate with the American College of Veterinary Surgeons in Minneapolis.
The drug Zubrin blocks the COX enzymes as well as a second type of chemicals, called leukotrienes, meaning it addresses two different inflammation pathways. This could make it more powerful than the others, says Dr. Boothe. While NSAIDs can be very effective, they also carry the risk of side effects, including damage to the dog’s gastrointestinal tract. They require careful dosing, and can’t be combined with other NSAIDs.
Corticosteroids, or Glucocorticoids. Veterinary glucocorticoids, including prednisolone and methylated prednisolone (Cortisate-20, Depo-Medrol and Medrol), are steroidal medicines that attack inflammation. Unfortunately, they also attack the dog’s tissues.
“As a pharmacologist, I have a real bias against using steroids to treat chronic pain,” says Dr. Boothe. Glucocorticoids can cause weight gain, incontinence and lethargy. Long-term, they’ve been linked to compromised immunity,muscle and bone loss, and a potentially fatal shutdown of the adrenal glands. Moreover, glucocorticoids actually damage cartilage. “Veterinarians have used them in older animals with the idea that they were the only thing that would relieve the dog’s pain,” says Dr. Boothe. “But now there are better options.” However, she says, glucocorticoids might be used in a one-time, direct-tothe- joint injection (see hyaluronic acid, following).
Hyaluronic acid, or HLA, is a natural source of PSGAGs (it’s found in connective tissue and synovial fluid).“We’ve had very good luck with HLA,” says James Cook, DVM, director of the Comparative Orthopedic Laboratory at the University of Missouri–Columbia College of Veterinary Medicine. “We do a series of three joint injections, the first with HLA and Depo-Medrol, and the last two with just HLA. It’s been very effective, even in dogs with advanced OA.”
HLA is also given orally, but there’s no evidence that it’s effective that way, says Dr. Boothe.
“Now, we’re looking at ways to spot arthritis before it gets too advanced,” he says. Researchers are also looking for genetic biomarkers—factors in the dog’s blood or joint fluid that would show the likelihood of his developing OA in the future. He encourages owners to know their dog’s predisposition for inherited joint diseases (the Orthopedic Foundation for Animals [offa.org] publishes dysplasia statistics for various breeds), then talk to a vet about ways to minimize the OA that might occur. “Anything that you do early in the dog’s life will have much more impact than what you do after the problem has developed,” he says.
The supplement industry is not monitored by the FDA, and studies have shown that the quality and amount of a supplement are sometimes less than indicated on the label. The adages “do your homework” and “you get what you pay for” apply.
Illustration by Thorina Rose