Cartilage is a slippery substance which acts as a buffer or “cushion” between the bones in a joint. It allows the bones to move over or around each other without pain. Arthritis occurs when the cartilage within a joint becomes damaged. Eventually an arthritic joint becomes inflamed and painful. There are over 100 different types of arthritis recognised in humans. In pets, the most common form is osteoarthritis, sometimes called degenerative joint disease. Other types include rheumatoid arthritis and septic arthritis which is caused by joint infection.
Arthritis commonly affects older and middle-aged pets. However, the condition is not limited to these age groups and younger animals can also suffer from the disease. When arthritis eventually causes changes in the joint which result in pain, this often becomes apparent by changes in the animal’s behavior – the primary symptoms of the disease. Because arthritis commonly develops with age, pet owners sometimes confuse changes in their animal’s behavior as normal age-related changes (such as a decrease in play), whereas in fact, the animal might be suffering quite severe arthritic pain.
Osteoarthritis is the most common form of arthritis. It is essentially caused by daily wear-and-tear of the joint, but can also occur as a result of injury. Osteoarthritis begins as a disruption of the cartilage; ultimately, this causes the bones in the joint to erode into each other. The condition may start with minor pain during your pet’s activity, but can develop into continuous chronic pain which might even occur when the animal is resting. Osteoarthritis typically affects the weight-bearing joints, but can affect both large and small joints of the body. Unlike rheumatoid arthritis, osteoarthritis is most commonly a disease of elderly pets.
Osteoarthritis, like rheumatoid arthritis, cannot be cured, but the condition can be prevented from worsening. Physiotherapy to strengthen muscles and joints can be helpful. Pain medications may be required. For some pets, weight-loss can reduce the stress on the joints thereby reducing the development of osteoarthritis.
Rheumatoid arthritis occurs when the body’s own immune system starts to attack body tissues. The attack is quite general and affects not only the joint but also many other parts of the body. This condition causes damage to the joint lining and cartilage. Eventually, this results in erosion of the opposing bones of the joint. Drugs used to treat rheumatoid arthritis include corticosteroids.
Symptoms of arthritis may not be particularly obvious in the early stages of the disease, but become apparent as pain in the joint increases. Symptoms may be particularly difficult to notice in cats as they tend to hide signs of injury or weakness.
An animal with arthritis may favor one or more of their limbs, or have a distinct limp. The severity and type of limp will depend on the joint/s that are affected. Limping is often more pronounced immediately after the animal wakes up from sleeping, and then becomes less pronounced as the animal begins moving about.
Because of the pain caused by arthritis, affected animals may become reluctant to move in ways with which they previously had no difficulty. For instance, arthritic cats might stop jumping up to high areas for sleeping, or may stop using litter trays with high sides. Dogs may not be able to sit so easily, jump in and out of cars, or get up and down stairs.
Arthritis can also affect various parts of the spine. This often results in an abnormal posture with a hunched back, a sore neck, or lameness in one or both hind legs.
Animals with arthritis become tired more easily. For dogs, walks may become shorter and your pet may spend more time sleeping or resting.
Pets with arthritis often lick, chew or bite the painful body areas. If this becomes severe, it may cause baldness over the affected area, or inflamed skin. Conversely, your pet may reduce its grooming because the movements are painful.
Changes in temperament
As with any condition that causes pain, your pet may become irritable if arthritis develops – they may bite, snap or vocalize when handled. It may be necessary to revise your petting or handling so that it does not cause pain.
Muscle atrophy is a decrease in the mass of muscles. This decrease can be partial or a complete wasting away. Arthritic pets can develop muscle atrophy due to inactivity. Atrophied muscles in the legs will give your pet the appearance of having legs thinner than usual.
Some cat breeds are more susceptible to arthritis than others. Hip dysplasia (abnormal development of the hip joints) is seen especially in Maine Coon, Persians, Siamese and other breeds. Patella luxation (dislocation of the knee cap) is more common in Abyssinian and Devon Rex breeds. In dogs, the larger breeds such as Labrador, Retriever, German Shepard and Alaskan Malamute are all more susceptible to hip dysplasia than other breeds.
Injury or trauma
Fractures, dislocations and other joint injuries can cause abnormal joint conformation and irregular future development. This can result in secondary osteoarthritis.
There is no evidence that obesity causes arthritis, however, it can make an existing condition worse.
Arthritis affects one in every five adult dogs in the U.S. It is one of the most common sources of chronic pain that veterinarians treat. In dogs, the joints most commonly affected by arthritis are:
• knee (stifle)
• wrist (carpus)
• ankle (hock)
• spine (intervertebral joints)
A study in 2002 concluded that 90% of cats over 12 years of age had evidence of degenerative joint disease. In cats, the joints most commonly affected by arthritis are:
• ankle (tarsi)
A veterinarian will be able to diagnose whether your pet has arthritis. They will perform a physical examination on your pet and may take x-rays. Occasionally, it might be necessary to take blood or joint-fluid samples to investigate possible joint infections.
Although arthritis cannot be cured, there are treatments available that can ease the pain for your pet.
The solution to keeping arthritic pets comfortable is not to limit their activity but to manage their pain. Initially, treatment for pain may need to be aggressive, especially if the pet has been inactive for a long time. As the benefits of exercise develop, the need for pain relievers often decreases.
Exercise is important for treating arthritis as it keeps strength in the muscles, tendons and ligaments surrounding the joints. If these supportive tissues become weak or loose, they can worsen arthritis. Exercise stimulates the production of joint-fluid which lubricates the joint and nourishes the cartilage. Exercise also keeps pets from becoming obese; extra weight increases the loading on joints making movement even more painful.
Nonsteroidal anti-inflammatories (NSAIDs) and opioid derivatives can be used in the treatment of arthritis.
Several diets or dietary supplements are available for pets with arthritis. These contain essential fatty acids to reduce inflammation, and glycosaminoglycans, the ‘building blocks’ of cartilage.
Acupuncture and low-level laser therapy have also been used in the treatment of arthritis in pets.