Arthritis Pain In Cats

Background

Housecats are believed to have evolved from the Middle Eastern Wildcat. It is now commonly believed that the cat actually domesticated itself, finding a ready source of food (rodents) around the early agricultural settlements.

Recent studies of the genetic composition of the modern-day housecat and its wildcat ancestor show that housecats have changed very little during the process of domestication. Perhaps this is because humans used cats for their natural talent in rodent control and did not apply artificial selection pressure (or selective breeding) to change the genetics of the housecat. It was not until the 19th century that cat fanciers began selecting cats for particular traits, which has led to the 70 or so breeds of domestic cat that we have today.

Given that their genes have changed little from their wildcat ancestors, it is no wonder the domestic cat has retained most of the behaviors and mannerisms of its close wild relatives. Today’s housecat has kept so much of its natural instincts and abilities that it can survive in the wild and hunt for its own food. Indeed, domestic cats signal and communicate with tail movements, postures, ear movements, etc., in almost identical ways to wildcats. Their ability to stalk, hunt, and take down prey also closely mimics their wildcat ancestors.

Common Feline Mucsculoskeletal Disorders

Musculoskeletal (MS) disorders are conditions that affect the bones, joints, tendons, ligaments, and muscles of the cat. Primary diseases of the bone in cats are rare. However, joint disorders are fairly common. The most common musculoskeletal disorder in cats is, by far, degenerative joint disease (DJD), also known as osteoarthritis or feline arthritis. One of the first studies into how common DJD is in cats was performed at NC State more than 15 years ago, and this study found that 90% of cats over 12 years of age had evidence of arthritis on x-rays (1). A more recent study by Lascelles and the team at NC State found that just over 90% of all cats have radiographic evidence of degenerative joint disease somewhere in the body (2). Other musculoskeletal disorders seen in cats include dysplasia of the hip, elbow, or shoulder; knee (patella) luxation; cruciate ligament disease; and tendon contracture.

DJD involves deterioration of all the components of the joint. This deterioration (of cartilage and the underlying supporting bone) results in inflammation and pain. In cats, the pain is most common in the hips, knees, hocks (ankles), lower back, and elbows. The condition is chronic and, with time, the pain may be so debilitating as to lead to a poor quality of life for the cat.

Diagnosing Musculoskeletal Disease and Pain

Like their wild ancestors, domestic cats are very good at hiding their pain. This, coupled with their typical lack of cooperation during a physical and orthopedic exam, can make diagnosing the pain and finding its source very difficult, even for the most experienced veterinarians. X-rays (radiography) and other imaging techniques are tools that can help diagnose a musculoskeletal condition; however, the source of the pain must first be localized. Therefore, a thorough history, including the owner’s assessment of changes in the cat’s behavior and activities, is essential for a diagnosis of musculoskeletal disorders and pain in the cat.

Changes in the cat’s daily habits that might indicate the cat is in pain include hiding, decreased grooming or excessive licking of a painful area, increased aggression when handled or agitation toward another pet, and avoidance of using the litter box (house-soiling). In addition, the cat’s mobility and activity level may be affected by the musculoskeletal condition and associated pain. Caregivers, therefore, may see a decrease in the cat’s willingness to jump up or down on obstacles, difficulty going up or down stairs, stiffness, less activity, an increase in time spent sleeping, and reluctance to play.

Diagnosing Cats in Pain

Although cats cannot describe their pain to us, the effects can be measured through evaluating behavior. A cat without osteoarthritis moves in a very fluid and (usually) graceful fashion. Pain associated with joint disease results in reduced or altered mobility, uneven or jerky movement, impaired ability to perform activities, and altered behavior. It is thought to disrupt sleep and impair cognitive function (thinking). All these multidimensional effects of pain appear similar to the effects in humans, and anything that pain affects can potentially be measured in order to measure the level of pain.

Chronic joint pain affects a cat’s behavior. It affects mobility and the ability to perform activities of daily living. People living with cats are best at assessing these changes. These changes can be captured using the FMPI (short form) questionnaire.  It often takes a little time to “tune in” to what to look for, and a few trial uses of the FMPI can help.

Managing Feline Pain and inflammation

The dominant approach to treatment of joint pain associated with DJD in cats revolves around medical management, with surgery being indicated occasionally. As for any chronic pain condition, a multimodal drug and non-drug approach is usually recommended to manage joint pain. Multimodal approaches use combinations of drugs with different actions (different modes of action). They also use non-drug therapies that work in different ways (such as dietary omega-3 fatty acids, massage therapy, and acupuncture). Some vets also prescribe the use of non-pharmaceutical anti-inflammatory devices, such as laser, therapeutic ultrasound, and pulsed electromagnetic field (PEMF) therapies. The reason for taking a multimodal approach is that chronic pain is complex and difficult to treat, especially in cats where drug toxicity and pilling challenges are common.

Unfortunately, little is known in veterinary medicine about what truly works to alleviate chronic pain in cats, although there is a lot of ongoing clinical research in this area. Such clinical research has told us that, just as in people, non-steroidal anti-inflammatories (NSAIDs) are effective for managing chronic joint pain, and that adding omega-3 fatty acids to the diet may also help alleviate joint pain. A new therapy – a once monthly injectable treatment – was recently approved by the FDA Center for Veterinary Medicine – a felinized anti-nerve growth factor monoclonal antibody.

Sources

1.  Hardje E M, Roe S C, Martin F R Radiographic evidence of degenerative joint disease in geriatric cats: 100 cases 1994-1997; J Am Vet Med Assoc 2002; 220; 628-32

2.  Lascelles BDX, Thomson Sumrell A, Henry III JB, Brown J, Simpson W, Wheeler S, Hansen BD, Robertson I, Zamprogno H, Freire M, Pease A. Cross-sectional study evaluating the prevalence of radiographic degenerative joint disease in domesticated cats. Veterinary Surgery 2010;39: 535-44.