NY Vet 2017: Osteoarthritis in Cats

Adequately managing osteoarthritis (OA) in cats vastly improves their quality of life, said Susan Little, DVM, DABVP, at the 2017 New York Vet conference in New York City. In her presentation, Dr. Little discussed the prevalence of OA in cats, the challenges of diagnosing feline OA, as well as various treatment options.

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OA in cats is underdiagnosed, said Dr. Little, co-owner of 2 feline practices in Ottawa, Canada. “[Cats are] often really good at masking their signs of orthopedic disease,” she noted. In addition, the disease is often bilateral, so gait abnormalities are harder to spot than they are with unilateral disease. Understanding these barriers to symptom recognition is a step toward making the diagnosis, she said. In cats, OA is more likely to be primary (idiopathic) than secondary. OA in dogs is more often secondary to hip dysplasia, trauma, or another cause. For veterinarians, this means that feline patients can have OA with no history of a predisposing condition.

Prevalence

The risk of OA “dramatically increases with age in cats,” Dr. Little said. Most senior cats have OA, she added. She recommended that veterinarians assume all cats over about 10 years of age have OA unless proved otherwise. The most common OA locations in cats are the elbow, knee, and hip. Some cats have lumbosacral OA accompanied by spondylosis. Dr. Little noted that arthritis in this location can cause signs similar to those of ataxia. Cats sometimes present for neurologic workup when the real problem is spinal arthritis, she said. She suggested keeping this in mind when presented with an older cat with ataxia but no other signs of neurologic disease.

Diagnosis

The first step in diagnosis, Dr. Little said, is having an “index of suspicion that your patients are likely to have OA.” She described a diagnostic triad of physical examination, radiography, and owner observations to help practitioners confirm the suspected diagnosis.

No specific diagnostic test exists for some feline medical conditions, she added. In these cases, a therapeutic trial can be part of the diagnostic process. “[OA] is one of the diseases in cats where response to treatment is a perfectly valid diagnostic tool,” she said.

Physical Examination

Dr. Little begins an examination of an older cat by gently palpating the entire body to locate sites of pain and then examining those areas last. “A good physical exam tip...especially with senior cats,” she said, “is to leave the difficult stuff, the painful stuff, maybe the stuff the cat doesn’t like...until the end.”

Localizing pain in cats is challenging. Dr. Little discussed several clues that a cat may be experiencing joint pain. Muscle atrophy from limb disuse can indicate chronic pain. Overgrown claws can be a sign of decreased mobility. Cats with arthritis may have unkempt fur because they do not feel well enough to groom or cannot groom themselves without pain. Cats may also overgroom painful areas, she said, suggesting that practitioners pay attention to bald spots over elbows or other joints. She also mentioned that a bald spot on the ventral abdomen of a cat with an otherwise normal coat can be a sign of bladder pain from idiopathic cystitis.

Cats with OA tend to develop joint pain and swelling. They are less likely to develop joint effusion, restricted range of motion, and crepitus, which are typical signs of OA in dogs.

Gait assessment is not always possible with cats, Dr. Little noted. She reminded the audience not to exclude OA from the differential diagnosis if a cat does not cooperate with an attempt to evaluate its gait.

Radiography

“Normal radiographs do not necessarily rule out OA in the cat,” Dr. Little said. “The problem is that cats... just have less radiographically evident pathology than dogs do.” Study results have shown that cats with OA are more likely to have cartilage changes than bone changes, she said.

Owner Observations

“We rely a lot on getting information from owners,” Dr. Little remarked. “Owners may notice changes in their senior cat. Whether they’ll report them to you is another matter.” Cat owners may think that arthritis signs are normal aging changes. She recommended asking owners specific questions about behavioral and physical changes and discussed tools that veterinarians and owners can use to uncover signs that a cat is experiencing chronic pain.

Videos and photographs of cats at home can yield important clues, she said. Videos of a cat grooming, getting in and out of the litter box, ascending and descending stairs, and jumping on and off furniture can be helpful. She also asks owners for photographs of cats resting. She pointed out that most cats at rest tuck in their forelimbs. A cat that consistently holds a forelimb in extension could be compensating for elbow pain, she said.

Dr. Little recommended giving owners a specific screening tool: the Feline Musculoskeletal Pain Index. This instrument was developed by the Comparative Pain Research Laboratory at the North Carolina State University College of Veterinary Medicine.¹ It is a 17-item questionnaire in which cat owners rate their pet’s ability to perform various activities, such as jumping onto the kitchen counter, climbing stairs, stretching, grooming, interacting with family members, and using the litter box. The tool includes instructions for scoring the responses. Dr. Little suggested having owners complete the questionnaire at home, ideally before the appointment, so they will have time to think through the responses. “The worst time to ask an owner to fill out a questionnaire is...when they’re in your clinic,” she said.

Dr. Little also recommended a brochure published by the American Association of Feline Practitioners that helps owners recognize signs of pain in cats.² The brochure describes behavioral changes that can indicate pain (such as hiding and becoming aggressive) and the importance of monitoring cats’ responses to therapy for chronic pain.

Treatment

The goal of treatment is to return cats to normal daily activities, Dr. Little said. Getting cats comfortable enough to interact with the family and use the litter box reliably is a worthwhile aim. Minimizing joint damage is beneficial but not necessarily the primary goal.

As with dogs, cats with OA often benefit from multimodal therapy. The choice of treatment modalities is specific to each patient and may change over time as new modalities are added, Dr. Little said.

Diet and Nutraceuticals

“I always prioritize weight loss,” Dr. Little said, adding that obese cats are 3 times as likely as normal-weight cats to be lame. Obesity puts extra stress on the joints and contributes to chronic low-grade inflammation, she noted.

Omega-3 fatty acid supplementation has been shown to improve activity levels in cats with arthritis, she said. Omega-3 fatty acids are available in various formulations, such as soft chews for cats, and are included in joint health diets. Dr. Little suggested checking the calorie content of joint health diets before recommending specific brands to owners of overweight (or formerly overweight) cats.

Chondroprotective agents like glucosamine/ chondroitin, polysulfated glycosaminoglycan, and pentosan polysulfate are available, but Dr. Little noted that very little published research has evaluated their use in cats. Because glucosamine/chondroitin is often included in supplements and diets that also contain other products, it is difficult to know whether the combination has an effect on its own. She concluded that although there is evidence that omega-3 fatty acids and joint health diets benefit arthritic cats, there are simply very few data on the efficacy of glucosamine/chondroitin in cats.

Drugs

In humans and dogs with OA, nonsteroidal anti-inflammatory agents (NSAIDs) are the cornerstone of treatment, Dr. Little said. However, only a single NSAID, meloxicam, is licensed anywhere in the world for long-term use in cats—but it is not licensed for this use in North America. In the United States, meloxicam is labeled for cats only as a 1-time subcutaneous injection for controlling postoperative pain.³ In Canada, where Dr. Little practices, meloxicam is labeled for cats as a single subcutaneous injection and is also available as an oral suspension for short-term (up to 4 days) control of perioperative or acute musculoskeletal pain.⁴

Using meloxicam to control chronic pain is off label in cats, so Dr. Little discussed precautions for practitioners considering it. She recommended using the lowest effective dose and stressed that the dose should be calculated according to the cat’s ideal body weight, not its actual body weight (for overweight cats). Her clinic’s medical record template includes a line for estimated ideal body weight for drug dose calculations. She also emphasized using feline-specific meloxicam formulations (such as the feline oral suspension available in Canada) for accurate dosing that is titratable to a cat’s weight.

She stressed choosing patients carefully for meloxicam administration. Meloxicam is a selective cyclooxygenase-2 (COX-2) inhibitor, so it is less likely than nonselective COX inhibitors to cause adverse effects such as kidney injury and gastrointestinal ulceration. However, patients receiving meloxicam should be stable and properly hydrated, she said. Owners must be able to watch for signs of toxicity at home and willing to bring their cats to the clinic regularly for monitoring. Dr. Little recommends reexamining cats and obtaining laboratory tests 2 to 4 weeks after beginning NSAID treatment. Cats should be rechecked periodically thereafter; the frequency depends on the patient’s condition.

Corticosteroids, anticoagulants, angiotensin-converting enzyme inhibitors, and diuretics can interact with NSAIDs, Dr. Little said. Cats receiving a corticosteroid (such as prednisolone to treat inflammatory bowel disease) should not receive an NSAID at the same time.

“About two-thirds of cats with OA also have chronic kidney disease,” Dr. Little said, noting that this is a common dilemma for veterinarians. She mentioned a retrospective study conducted in Australia (where oral meloxicam is labeled for long-term use in cats⁵) whose results showed that meloxicam administered for longer than 6 months did not exacerbate preexisting chronic kidney disease, compared with kidney disease in cats not receiving meloxicam.⁶ She pointed out that the cats in this study had stable disease, emphasizing the importance of careful patient selection. The FDA requires a warning on the package insert of the injectable product not to use meloxicam in cats with kidney dysfunction.³

Dr. Little discussed 3 other drugs that can be used for pain control in cats with OA: gabapentin, buprenorphine, and tramadol. Gabapentin is probably the most commonly prescribed second-tier drug for cats that cannot receive NSAIDs, she said, although there are few published studies on its use for feline arthritis. Dr. Little typically prescribes transmucosal buprenorphine only for short-term use, either to manage breakthrough pain in a cat taking other medications or as a response-to-treatment trial in a cat with suspected OA. She does not prescribe buprenorphine for long-term use, she said, because of the potential for patients to develop tolerance to opioids. Tramadol has a bitter taste that makes it difficult to administer to cats, and it can also cause dysphoria. “No matter what drug you use,” she reiterated, “these guys do need regular reevaluation.”

New drugs for chronic pain management in cats are in development, said Dr. Little. These include a monoclonal antibody and a feline-specific anti—nerve growth factor antibody.

Environmental Modification

Dr. Little recommends raising arthritic cats’ food and water bowls. Elevated bowls let cats with elbow arthritis eat with their elbows extended (which is less painful than holding them flexed) and give cats with hip and stifle pain a more comfortable sitting position while eating. Litter boxes should be relocated if necessary to make them easy for cats to access. Tall litter box sides may need to be cut down. Dr. Little also suggested providing steps to cats’ favorite areas (like beds and window perches) so they do not have to jump.

Other Options

Physiotherapy and rehabilitation can be useful for cats with arthritis, Dr. Little said. Acupuncture and laser therapy for feline OA have not been well studied, she added.

Conclusion

“This is a huge quality-of-life issue for me and a human—animal bond issue for me,” Dr. Little said. Recognizing and managing feline chronic pain makes life better for cats and for their owners.

Dr. Walden received her DVM from North Carolina State University, followed by an internship in small animal medicine and surgery at Auburn University. She is a board-certified editor in the life sciences and the owner of Walden Medical Writing, LLC. Dr. Walden writes and edits materials dealing with human and veterinary medicine. She has also been a practicing primary care veterinarian for many years.

References:

• Feline musculoskeletal pain index. North Carolina State University College of Veterinary Medicine website. cvm.ncsu.edu/research/labs/clinical-sciences/comparative-pain-research/labs-comparative-pain-research-clinical-metrology-instruments-subjective-nighttime-restlessness-evaluation-snore/. Accessed May 28, 2018.
• How do I know if my cat is in pain? The Cat Community website. catfriendly.com/feline-diseases/signs-symptoms/know-cat-pain/. Published 2017. Accessed May 28, 2018.
• Metacam [package insert]. St Joseph, MO: Boehringer Ingelheim Vetmedica GmbH; 2014.
• Metacam oral suspension for cats [package insert]. Burlington, ON: Boehringer Ingelheim (Canada) Ltd; 2012. boehringeringelheimcanada.cvpservice.com/product/view/1230123. Accessed May 28, 2018.
• Metacam oral suspension for cats [package insert]. North Ryde, New South Wales, Australia: Boehringer Ingelheim Pty Limited; 2014. files.boehringer.com.au/files/CMI/Metacam%20Oral%20Suspension%20Cat%20ANZ.pdf. Accessed May 28, 2018.
• Gowan RA, Lingard AE, Johnston L, Stansen W, Brown SA, Malik R. Retrospective case-control study of the effects of long-term dosing with meloxicam on renal function in aged cats with degenerative joint disease. J Feline Med Surg. 2011;13(10):752-761. doi: 10.1016/j.jfms.2011.06.008.