Diagnosing Feline Chronic Pain Associated with Osteoarthritis

When it comes to osteoarthritis (OA) or degenerative joint disease (DJD) in cats, diagnosis can be a significant challenge for veterinarians. 

In-clinic evaluation of OA pain in cats can be problematic for many reasons—we have all 
experienced cats, unsure of exam room surroundings, that freeze at the back of the 
transport carrier or dive under the nearest cupboard to hide. Even cats that are happy to sit out on the table may not like to be manipulated or have certain parts of their body touched—did they pull away due to pain or frustration? Pet owner information is therefore a fundamental part of the diagnostic process, but information from the home environment can be lacking. Many pet owners aren’t aware or don’t always pick up on their cat’s behavioural changes caused by OA. 

While OA currently cannot be cured, our aim is to manage our feline patients’ pain. But 
first, we should explore ways to help us diagnose this tricky disease. 

 
Is Your Client’s Cat Suffering from Osteoarthritis? 

 
An estimated 40 percent of all cats show clinical signs of OA and a much larger number have radiographic changes associated with disease ⁽¹⁾. In an important study, over 90 percent of the cats examined had radiographic evidence of degenerative joint disease ⁽²⁾. The burden of OA increases with age ^{(2, 3)} but the disease doesn’t just affect older cats: A 
large number of young cats (even those < 5 years of age) can be affected ⁽²⁾. But while the data tells us that this condition is common, the number of cats diagnosed and receiving treatment appears to be much lower ^{(4, 5)}. 

 
Perhaps we should not be surprised if the number of cats treated for the disease does not match study estimates, given the multiple diagnostic challenges that feline DJD poses for veterinarians? The difficulties associated with in-clinic assessment have already been mentioned, but many cats may not even see a veterinarian until the disease is advanced. Concerns about transportation and other stresses can be one reason that cat owners may avoid visits to the clinic, but many pet parents probably aren’t even aware that their cat is In pain. Cats rarely demonstrate lameness as a sign of osteoarthritis and their other 
behavioural changes can be subtle or may be mistakenly attributed to “old age” ⁽⁴⁾. Cats are also known to hide their pain ^{(4, 6)}. 

The likely under-recognition of the signs of feline OA ⁽⁴⁾ has many knock-on implications. Everyday activities such as grooming, using scratching posts, playing and jumping—all natural behaviours that cats need to express—can become uncomfortable, and therefore avoided, by cats with OA pain ⁽⁷⁾. Without being able to display their natural behaviours, 
cats can become anxious and stressed. Feline stress and pain may also affect your client’s relationship with their cat—maybe their cat doesn’t want to be picked up anymore or won’t jump up to lay in their lap? Approaching the hidden pain of osteoarthritis is not only important for the comfort and well-being of the cat, but it could also help prevent pet parent dissatisfaction and support the human-animal bond. So what can we do to reveal the signs of OA? 

 
Signs of Osteoarthritis Pain in Cats ^{(1, 7)} 

 
Although signs of osteoarthritis pain in cats can be subtle and easy to miss, pet owners can be your eyes at home if they know what to look for: 

 
Increasing your clients’ understanding of OA can help them be even more in-tune with their cat’s behaviours and quickly identify any changes. Images and animations, showing how feline OA changes their cat’s activities, can be very visually engaging educational tools. Even if pet owners are only able to identify one area of concern, without realizing that other changes linked to osteoarthritis pain are occurring as well, it could help them seek advice sooner. Reports show that pet owners can frequently identify that their cat is 
unwilling to jump or has an inability to jump as high, if questioned ^{(1, 7)}, so providing opportunities to proactively capture pet owner feedback—such as at vaccination visits—is important too. 

 
Many pet owners do not see other chronic changes in their cats, such as muscle atrophy, but it is an important change to point out to them once the cat is seen at the clinic. Some clinics have a cat evaluation area consisting of climbing frames and other play apparatus. Depending upon the personality of the cat, these areas can be useful for observing the movement of the cat while obtaining additional information from the pet owner. Lameness is rarely noted when assessing a cat for osteoarthritis because joints are commonly 
bilaterally affected. 

 
Much of the initial detective work needs to be done at home, so motivated and OA educated pet parents are an important part of your feline care team. Long-term, chronic pain and the associated physical changes can be difficult to control, but disease management can start from a stronger base if the signs are identified quickly. 

 
How to Diagnose Chronic Pain Associated with OA in Cats 

 
There are several pieces of the puzzle that may aid in diagnosing chronic pain associated with OA in cats, including: 

 
Questioning of pet parents is without doubt an important part of OA diagnosis in cats. Since changes can be subtle, and cats act differently at the veterinary clinic than they do at home, understanding the behaviour of cats in their at-home environment is key. It is important to identify any changes in behaviour—not just changes in what the cat does but asking questions to identify what the cat does not do. Clinical metrology instruments—pet owner questionnaires (discussed later)—can help to capture such information. All cats should express normal behaviours such as scratching or grooming, so identifying a cat that is reluctant to groom or is not using its scratching post as often, could be an important indicator of pain. 

 
Consider asking your clients to take videos of their cat at regular intervals to provide a 
visual log and help monitor for any changes. Videos of the cat climbing up and down stairs, jumping on and off high surfaces or furniture, or chasing and running are particularly useful ⁽¹⁾. While cats don’t often limp with osteoarthritis, they do show other 
abnormalities such as stiffness, hesitancy to jump and increased noise upon landing. Of 
course, changes in behaviour can occur for a variety of reasons and are not always due to OA pain. Other causes of chronic pain, cognitive dysfunction, changes in the home, or a need for increased enrichment can all cause behavioural changes in cats, but a similar approach— gathering more information from pet owners and a full medical examination of the cat—can help identify possible causes. 

 
A thorough physical examination is a key part of patient evaluation and a full orthopaedic examination should be included whenever possible—especially if DJD is suspected. As much as possible, cats should be allowed to express their natural behaviours in the veterinary examination room. Allowing cats to walk around the exam room, come out of the carrier on their own, jump down from the exam table, or even jump onto a nearby countertop or sink can all increase the opportunities for witnessing subtle changes in behaviour or gait. 

 
Diagnostic tests are key to ruling in or out, not only osteoarthritis, but other medical 
conditions as well. Blood work and urinalysis are useful to evaluate general health status and radiographs should be taken to confirm any diagnosis of DJD/OA. It is important to 
remember that radiographic signs don’t always correlate with clinical signs of the disease ^{(4, 8)} but radiographs can help determine an overall DJD score ⁽²⁾ as well as rule out any other causes of musculoskeletal pain. 

 
Sometimes, a trial period of pain control medication can support the diagnosis of chronic OA pain. Pet parents may not always be able to recognize that their cat is having 
mobility/activity problems until they see the difference that treatment can bring. However, it is important that they understand that cats chronically affected by OA have learned to adapt their behaviours, and may not immediately return to previous activities. Observable benefits have been most commonly reported after a few weeks of treatment, in feline OA pain management studies ^{(9, 10)}. A multimodal approach to treatment is also recommended. Disease management plans should include environmental enrichment in addition to pain control medication. Different types of therapies to complement pain 
medications are also important considerations and could include joint health supplementation, weight loss, physical therapy, or other alternatives such as acupuncture. 

 
Specific Tools to Help Diagnose Osteoarthritis in Cats ⁽¹¹⁾ 

 
Pain scales for use in cats with chronic pain have been developed to aid diagnosis and 
monitoring. Three well known pain scales are appropriate for use in cats with OA and are questionnaires completed by the cat’s owner: 

All of the pain scales evaluate the impact of chronic pain in slightly different ways. For 
example, the CSOM assesses the impact of pain on activities specific to that cat (including time and place), the FMPI uses 17 standardized items to assess mobility, ability to perform daily activities and interaction with other pets and people, and the MI-CAT(C) uses the most items to evaluate many aspects including agility, normal behaviours, self-maintenance, 
and physical condition ⁽¹²⁾. 

The MI-CAT(C) questionnaire also has a partner tool the MI-CAT(V) which involves 
assessment of movement and posture by veterinarians. It is greatly aided by having pet owners take a variety of videos at home during their cat’s normal activities. 

 
When left untreated, chronic pain due to osteoarthritis negatively affects the welfare of the cat, the cat’s daily activities, and the human-animal bond. While a keen understanding of natural feline behaviours and experience with orthopaedic issues in cats are key to identifying chronic pain due to OA, collaboration between pet owners and veterinarians can be a very powerful tool.