Arthritis in Dogs and Cats

Joints are located wherever two bones come together. There are many joints in the body, and several different types of joints. The type of joint most commonly affected by arthritis is called a diarthrodial joint. This type of joint is made up of two bones and a joint capsule. The knee (or stifle) is a good example of a diarthrodial joint, and one commonly affected by injury and arthritis. Dogs and cats both have more than 200 bones in their bodies. The actual number varies by the length of the tail. With all of these bones and joints, there is a lot of potential for a problem.
Arthritis develops secondary to trauma or to a developmental abnormality in the joint. When the normal mechanics of the joint are disrupted, surfaces don't glide smoothly across each other. Friction in the joint invites the presence of inflammatory factors, which then cause further destruction of the normal cartilage. An interesting study that followed Labrador Retrievers with a genetic predisposition to hip dysplasia for 14 years, found that restricting food intake and maintaining a lean body condition greatly reduced the incidence of osteoarthritis in these "at-risk" dogs. Another interesting finding of the study was that some dogs had no evidence of arthritic changes radiographically (x-rays) until 10 years of age, after which they developed changes in their hip joints that were obvious on x-ray films.
The aging process results in a decrease in the body's production of glucosamine and chondroitin. Glucosamine and chondroitin are two important compounds for the health of the joints. Glucosamine is a building block for normal, healthy cartilage. Chondroitin is also a building block for normal cartilage but has the added job of helping to block enzymes that can damage the cartilage. These two compounds are called "nutraceuticals". Chondroitin is manufactured from the cartilage of animals, usually the trachea of cows. Glucosamine is manufactured from the shells of certain shellfish, like shrimp or crabs. Nutraceuticals are not regulated by the FDA and therefore can vary in their composition and effectiveness. Using a brand name, veterinary form of glucosamine and chondroitin is a good idea.
There are many treatments available to help dogs deal with the pain of osteoarthritis, but there are not as many available for cats. Aspirin is one medication that can be used and may help some dogs and cats with the pain associated with arthritis. Cats metabolize this medication very slowly, so it is usually only given once or twice weekly. We used to recommend enteric-coated aspirin to help protect the stomach from ulcers, but it has been found that the digestion of this coating can be unpredictable. We now recommend non-coated aspirin. Because of potential side effects associated with aspirin use (bleeding disorders, stomach ulcers, toxicity), aspirin should only be used under the direction of a veterinarian. Other non-steroidal medications (NSAIDS) have been developed as safer and more effective alternatives to aspirin. These are available as prescriptions from your veterinarian. (Pfizer has an approved veterinary NSAID, see their website for more information).
Alternative therapies, such as massage, physical therapy, and acupuncture are used in some areas where they are available. Mild, but consistent, exercise is important for pets suffering from arthritis. Swimming is a great option for dogs that like the water. Excess weight is a problem for all pets, but is especially painful for arthritic pets. Keep your pet in lean body condition to ease the discomfort of osteoarthritis. Many veterinarians have resources available to you about arthritis and your pet. Ask your vet today.
Drs4Pets is a collective of veterinary professionals with diverse backgrounds--clinical vets, corporate vets, consultants and authors-- and a shared interest in animal health and pet nutrition.