March 4, 2021 – A sudden slip on a tile floor. A missed countertop. A slow climb up the stairs. Osteoarthritis can show up in a hundred different ways in dogs and cats. It’s a disease shared with aging humans and can seriously impact the quality of life for our pets.
Age is a risk factor for osteoarthritis in cats and dogs, but the disease is diagnosed in younger pets, too. Osteoarthritis affects approximately 14 million adult dogs in the United States alone, and owners consistently report it as a top health concern. Although the number of cats affected is unclear, what is known is that 90% of cats over 12 years of age show X-ray evidence of osteoarthritis. Taken together, this represents a huge number of pets affected by this condition.
What is osteoarthritis?
Osteoarthritis (OA), also known as degenerative joint disease, is a progressive disease of the joints fueled by chronic inflammation. The end result is a chronic pain state that can have far-ranging, negative health effects beyond an affected joint.
It’s still not entirely clear what initiates the process of inflammation in many cases, although sometimes an inciting cause is obvious (such as joint trauma).
Although most people think of osteoarthritis as a disease of bone, it’s really a disease of cartilage. Research shows that cartilage is in a constant flux of remodeling, with factors favoring degradation of cartilage in balance with cartilage re-building activities. The process continues throughout our pets’ lifetimes.
For reasons that aren’t clear, this balance can be disrupted and, in osteoarthritis patients, the forces that result in cartilage deterioration far outpace the repair forces, ultimately leading to cartilage loss which gives rise to the clinical signs and pain associated with the disease.
Lastly, there is evidence that osteoarthritis is not simply a normal outcome of aging. When researchers compare cartilage from individuals suffering from osteoarthritis to cartilage from older individuals without OA, some similarities are evident, but in other aspects the tissues are very different. This indicates that OA is a disease and not an inevitable outcome for our elder pets.
Understanding pain in animals is a key to diagnosis and treatment
Pain relief is the driving force for owners and veterinarians when it comes to treating pets with OA. Understanding pain responses is important both for diagnostic testing and treatment of OA.
Pain perception is a complex phenomenon that incorporates not just a body’s pain receptors but also includes stress responses, the environment, genetics, past experiences and emotions. All of these factors can influence an animal’s perception of pain as well as play a role in the success – or lack thereof – of treatment strategies.
Chronic pain, such as that seen with OA, also can lead to hyperalgesia (heightened pain perception to painful stimuli), and allodynia, (pain perception caused by a usually non-painful stimulus). The consequence is a vicious cycle of increasing pain. A better understanding of the pain perception process is driving the development of new treatments and leading pain experts to re-evaluate how we approach pain relief in pets.
Making the diagnosis
Osteoarthritis in cats and dogs is diagnosed by a combination of history, physical examination, special tests and, often, response to therapy. Although dogs and cats share a common pathologic process when it comes to OA, there are important differences between the two species when we look at clinical signs and treatment.
Orthopedic specialists suggest that most osteoarthritis in dogs arises secondary to developmental diseases such as hip or elbow dysplasia. Previous trauma, aging or exercise are NOT thought to inevitably lead to OA, which is consistent with the scientific evidence recently published for people.
Because dogs share many activities with their owners, and are usually exercised regularly, there are many opportunities for owners to notice changes associated with OA in dogs early in the disease process.
The most common signs reported in dogs with OA are:
- Lameness (by far the most common)
- Stiffness on rising
- Reluctance to engage in play or seeming to tire more quickly
- Reluctance to jump
- Altered gait
- Increased irritability
- Reluctance to be touched or petted
A good physical examination, including assessment of gait and muscle strength, is helpful in focusing in on the affected joint(s).
For many years, veterinarians believed that most cats didn’t develop osteoarthritis, which seems strange in hindsight. There were many reasons why arthritis in cats was tricky to diagnose, including a cat’s tendency to hide illness and difficulty in examining cats for pain.
Unlike what we see in dogs with OA, cats often have bilateral disease, meaning that they won’t favor one side or the other because everything hurts! In addition, cats and their owners interact in different ways; most owners don’t walk their cats or play catch or fetch, activities in dogs that often uncover pain or altered mobility. Veterinarians also can attest to how the stress of simply taking a cat for a veterinary exam can mask pain.
In addition to the physical exam, there are questionnaires available for both veterinarians and owners to assess pain in cats. The Feline Musculoskeletal Pain Screening Checklist (Feline MiPSC) was recently developed as a screening tool to assess cats for pain. Once a cat has been screened using this instrument, experts recommend using other questionnaires, such as the Feline Musculoskeletal Pain Index (FMPI), the Client-Specific Outcome Measures (CSOM) or the Montreal Instrument for Cat Arthritis Testing (MICAT - there are two surveys, one for caretakers and one for veterinarians) as a way of monitoring efficacy. Other questionnaires also are available for veterinarians or are in development.
The questionnaires might sound like a mouthful (and a bit of a hassle to fill out) but data suggests they’re very helpful in objectively assessing OA in cats, when used both by veterinarians and cat owners.
Although diagnosis is challenging, there are clinical signs owners can look for that that point to OA. Interestingly, in cats, almost all the signs are tied to behavior changes. The most common clinical signs include:
- Hesitancy or avoidance of jumping
- Reluctance to go up or down stairs
- Using a step to get onto a surface instead of jumping
- Decreased interactions with owners or other animals
- Increased irritability
- Decreased food and water consumption
- Resents being brushed, patted or touched
- Greasy hair coat and dirty nails
- Elimination accidents – difficulty getting in or out of the litterbox
- Sudden vocalization and running away for no apparent reason
- Suddenly turning to look at a region of the body for no apparent reason
The bottom line for cat owners is that in cats, unlike dogs, behavior changes are dominant when it comes to OA. Unfortunately, some of these signs overlap with other cat diseases such as hyperthyroidism and kidney disease. It’s important for owners to regard any behavior changes as potential signs of disease and not simply a product of aging.
Other diagnostic tests are sometimes used in both dogs and cats to diagnose OA. X-rays remain a standard and often-used way of ruling in or out OA, but research shows that X-ray findings don’t always correlate with the degree of pain or impaired mobility experienced by a patient. Although they are a good place to start, X-rays occasionally can be misleading.
Additional tests usually require referral to a veterinary teaching hospital or other referral facility. While most cases of OA don’t require advanced testing, MRI, CT scans, evaluation of joint fluid and arthroscopy sometimes are used to help with diagnosis.
Numerous options are available to treat osteoarthritis, with drugs used to alleviate pain a cornerstone of therapy. However, questions remain regarding which therapies are most effective, and the search for safer, more effective treatments continues.
Treatment options for osteoarthritis fall into several categories, and veterinarians work with pet owners to find options from each category to provide relief for their patients.
Treatment of OA includes:
- Weight management – there is universal agreement that this is a key component of any treatment plan.
- Non-steroidal anti-inflammatories (NSAIDS) – these medications are a foundation of OA treatment, and good objective data in both dogs and cats demonstrates their effectiveness.
- Narcotics – although often prescribed for OA, recent research suggests they aren’t very effective for this purpose.
- Injectable medications – which are used to improve cartilage composition.
- Miscellaneous medications – examples include gabapentin and amantadine
- Supplements – omega 3 fatty acids and glucosamine/chondroitin preparations can be used as adjunct therapy.
- Physical therapy – can help maintain muscle strength.
- Acupuncture – can be beneficial and, as an adjunct, can allow for the reduction of pain medication.
- Surgery – rarely needed nor beneficial in most cases.
- Environmental modifications – no-slip surfaces, ramps for climbing into cars and baby gates where needed to prevent falls.
- Emotional support – emotions can affect pain response, so providing a supportive environment with lots of attention, cognitive stimulation and environmental enrichment can help with pain management.
Many medications are available to treat osteoarthritis in both dogs and cats. Drug selection depends on many variables including medication costs and availability, and the presence of concurrent diseases. Especially in the case of NSAIDS, owners need to work with their veterinarians to determine which medication is best. Owners should NEVER administer any medications to their pets without first consulting with their family veterinarian!
New therapies on the horizon
The progressive nature of OA means many treatments fall short of providing adequate pain relief. In addition, older pets with concurrent conditions preclude the use of some medications, limiting therapy choice. Lastly, many therapies are associated with significant side effects, limiting their use in some patients.
Because of the need for more effective and better tolerated treatments, veterinary researchers are looking at new, innovative therapies to address pain in dogs and cats. Some new therapies currently in development include:
- Antibodies directed against pain pathways have shown promise in early trials.
- Stem cell therapy has shown some promise, and many research teams are working to optimize this therapy in dogs and cats.
- Cannabinoids have received a lot of attention in both human and veterinary medicine and is another area of active research.
- Platelet-derived products are currently being adapted from human and equine medicine for dogs.
Many of these therapies haven’t been tested in rigorously controlled studies but we expect to see more activity here in the next few years. Other complementary therapies also are under study and ultimately could be used as adjuncts to more conventional treatments.
It’s important to work with your veterinarian to determine what therapy (or combination of therapies) are best for your pet. One size doesn’t fit all, and even a patient initially well controlled on one therapeutic plan may need treatment adjustments as the disease progresses.
An important component of any therapeutic protocol is careful evaluation of treatment success, a notoriously tricky problem when dealing with pain management. Many studies, both in human and veterinary medicine, show the placebo effect is particularly strong when it comes to evaluating response to pain therapy. The questionnaires mentioned above were designed not only to diagnose OA but also to objectively evaluate a patient’s response to therapy. Objective measurements help fine-tune treatment.
Several risk factors affect the development of osteoarthritis in people that veterinary experts feel are likely also true for animals. They include:
- Metabolic disease (such as diabetes)
- Previous injury
Although we can’t stop the aging process, owners can take steps to try to keep OA at bay.
First and foremost is maintaining a lean body mass throughout a pet’s life. Just as in people, it’s much more difficult to lose excess weight than to avoid weight gain from the start. In dogs, it’s important to avoid rapid growth as puppies, especially in the larger breeds.
Since growth abnormalities play a role in later development of OA, monitoring for, diagnosing, and treating these conditions early can help stop or delay the development of OA later in a dog’s life.
Finally, routine physical examinations by your veterinarian can help detect diseases that can contribute to OA as well as detect OA in its earlier stages, which in turn means starting appropriate therapy to slow its progression.
Learn more about Morris Animal Foundation-funded studies focused on osteoarthritis and find out what you can do to help us make dogs and cats suffering from this disease live healthier, happier lives!