Geriatric feline patients are no different from any other species in their propensity to develop arthritis and chronic pain with age.  They do however pose a unique challenge in managing this pain, making therapy methods different and more complex in comparison to other species.  The incidence of chronic pain in cats is not well documented, but feline osteoarthritis and degenerative joint disease has been radiographically recognized in a significant portion of the feline population, some estimations quoting as high as 90% of cats over the age of twelve years of age may be affected.  Osteoarthritis is often a painful disorder that can have a severe impact on a cat's quality of life.  It is therefore important that caregivers are well informed on the disease process and familiar with the variety of therapies available so they may make the most appropriate management decisions for their companion under the care and advisement of their veterinarian.

Degenerative joint disease involves the deterioration of the articular cartilage and is most commonly associated with age-related changes from chronic use over the years.  A joint is defined as any junction of two or more bones, whereas a synovial joint is defined as a moveable joint.  Synovial joints are composed of a joint capsule that secretes protective and lubricating synovial fluid that nurtures the articular cartilage.  The articular cartilage is the protective layer that covers the surface of the junction of any synovial joint.  These components allow for a smooth, controlled and protective movement of a joint.  Degeneration of the articular cartilage leads to inflammatory changes of adjacent tissues within the joint and is then termed osteoarthritis.  This inflammation results in an alteration in the synovial fluid of the joint capsule, ultimately decreasing the nutritional supply to the articular cartilage and leading to increased damage.  The most common joints that seem to be affected in the cat are the shoulder and elbow.  This could be attributed to the cat's propensity of jumping from tall or long distances and the resulting repeated impact on these inflicted joints.  Intervertebral disc disease is also a common source of chronic pain in the cat.  Often resulting in the narrowing of vertebral segments within the lumbar-sacral region, compression of the intervertebral discs, and associated impingement of exiting nerve roots to the limbs.

Cats tend to be fickle creatures, making their signs of pain often subtle and non-specific, therefore easily missed by a caregiver.  Chronic pain in the feline is often accompanied with behavioral changes and only occasionally with an obvious physical impairment such as lameness.  These behavioral changes may be easily overlooked or assumed to be inevitable with the preconception of the effects of advancing age.  The most common signs indicative of chronic pain in the feline patient include decreased grooming, reluctance to jump up or down, and soiling outside the litter box.  Other changes might include altered sleeping habits, decrease in activity, withdrawing from human interaction, stiffness, hiding, and aversion to being stroked or brushed.

Life-style changes including weight loss and physical therapy are excellent options for controlling the progression of the disease and offering the feline relief from discomfort.  Weight loss is one of the most effective management tools to alleviate the inciting cause of the pain.  The loss of excessive weight with gradual diet restriction is an ideal form of management that can have profound effects that decrease the strain and stress on affected joints and ultimately improve the overall health of a cat.  It is important that a cat's diet is adjusted under the supervision of a veterinarian because cats have the potential of developing hepatic lipidosis when drastic reductions of food are made.  Weight loss should be carefully monitored to ensure a steady reduction.

Non-steroidal anti-inflammatory drugs (NSAIDS) are the most common therapy prescribed to other species for the management of chronic pain.  However, NSAIDS are not as readily prescribed to feline patients due to alterations in the cat's ability to metabolize this class of drug.  NSAIDS are cleared from the body through metabolism in the liver, also called the hepatic system, most commonly through the process of glucoronidation.  Due to an evolutionary deficiency in this metabolic pathway, cats have a low capacity to handle drugs that require hepatic glucoronidation, leading to decreased clearance of the drug and increased toxic effects.  Metacam (meloxicam) is currently the only NSAID approved for use in cats in the United States.  Due to the risk of renal, liver and gastrointestinal toxicity the drug should only be used under strict supervision of a veterinarian at the lowest effective dose.  The beneficial response and degree of improvement Metacam offers feline patients has been thoroughly studied and is encouraging however continual reassessment and monitoring with bloodwork and a urinalysis is necessary to evaluate the cat's continued ability to tolerate the drug, especially with long-term use.

Opioids tend to be the most commonly used and relied upon drug for treating pain in the feline patient.  This class of drug offers excellent pain control but is most appropriate for short-term acute situations.  Opioids can cause increased sedation and altered behavior; long-term use could lead to tolerance and or dependence, requiring larger dosages in the future.  Therefore, another drug selection may be warranted when looking for long-term comfort and control of a feline arthritic patient experiencing chronic pain.

Gabapentin is an anticonvulsant that has been found to be effective in the treatment of neuropathic pain in people.  Studies have reported similar responses to be present with the use in felines.  The mechanism of the drug is currently unknown, however it has been shown to be an effective option for long-term pain management in cats, especially for managing pain from intervertebral disc disease.  The drug has a large dosage range allowing for greater flexibility as compared to other classes of drugs to find the optimum dosage for each individual cat.  This dosing adjustment is done by weighing the ability to alleviate pain without causing unnecessary sedation.  The medication is often distributed in a capsulated form, however compounding services are available to assist in a convenient administration of the drug in other forms such as flavored liquids.

Glucosamine chondroitin is a chondroprotective agent aimed at restoring and promoting the synthesis of molecules essential in providing a healthy environment for articular cartilage.  These molecules promote the restoration of articular cartilage suffering from the destructive state of osteoarthritic joints.  Glucosamine has been found to be a safe drug with no proven ability to exhibit toxicity at high oral dosages.  Research has concluded that the drug is effective as both an anti-reactive and anti-arthritic agent in controlling osteoarthritis in animal studies.  Glucosamine chondroitin is offered in a number of different formularies making it easily obtainable, relatively inexpensive, and in different preparations giving the caregiver a variety of options for administration.  However, because the drug is classified as a nutrient, alleviation of clinical signs may take up to 6-8 weeks to be seen.

Recently there has been an aggressive integration of alternative or adjunctive treatments for chronic pain in human medicine, likewise veterinary medicine has followed suit.  Many veterinary clinics are now offering options such as acupuncture, massage, and physical therapy and find that many cats tolerate these treatments surprisingly well.  The response to these therapies is more difficult to evaluate due to the individual variation and inconsistency with the modalities; however qualitative research has shown an overall improvement in many patients.  Since these forms of treatment, when preformed by properly trained practioners, have little risk of negative effects they can safely be integrated into a larger pain management program for aging cats.

Providing a good quality of life to our feline companions of advancing age is a balance of careful observation for subtle signs and thoughtful consideration of the risks and benefits of available pain management options.  As with anything, an ounce of prevention is worth a pound of cure and for the cat this comes in the form of weight management to minimize the stress on aging joints.  This said, even the fittest of cats may eventually develop joint changes that require medical intervention, and although not abundant, pain management options do exist to help alleviate discomfort and enhance the cat's overall quality of life.

References:

B Ducan X Lacelles.  "Nonsteroidal anti-inflammatory drugs in cats: a review."  Veterinary Anaesthesia and Analgesia.  2007, 34, 228-250.

Bennett, David; Carolyn Morton.  "A study of owner observed behavioral and lifestyle changes in cats with musculoskeletal disease before and after analgesic therapy."  Journal of Feline Medicine and Surgery.  2009. 11, 997-1004.

Burnakis, G. Thomas.  "Gabapentin for Leg Cramps: Muscling IN on Quinine"  Hospital Pharmacy.  2000. Volume 35, Number 8, 887-890.

Davis, W. Marvin.  "The role of glucosamine and chondroitin sulfate in the management of arthritis."  Nutramax Laboratories, Inc.  April 1998.

Hungerford, S. David.  "Treating Osteoarthritis with Chondroprotective Agents."  Orthopedic Special Edition.  Reprinted from January-April 1998.

Moore, A. Gareth.  "Degenerative joint disease, pharmacology and therapeutics of treatment."  Veterinary Medicine Report.  1990. 2, 89-96.

Neil, M. Kristen.  "The role of glucosamine and chondroitin sulfate in treatment for and prevention of osteoarthritis in animals."  JAVMA.  Volume 226, No 7, April 2005.

Robertson, A. Shelia.  "Managing Pain in Feline Patients"  Vet Clin Small Animal 2008.  Volume 38, 1267-1290.