Let’s start with two astounding statistics that relate to feline degenerative joint disease (DJD):
- Nine out of 10 cats show evidence of DJD on radiographs—even 6-month-old kittens!1
- One in five cats in the United States is over the age of 11 years.2
DJD is a common but often unrecognized condition in cats, causing chronic pain and preventing cats from performing normal feline behaviors. Since the disease is progressive, it worsens with age and clinical signs increase. Ilona Rodan, DVM, DABVP (feline practice), discussed the condition at a recent Fetch dvm360 conference. If DJD is untreated, she explained to her audience, the cat’s social relationships within a household can change and patient welfare can suffer.
By being aware of DJD, its incidence, the joints it affects, the pharmacologic options available, other multimodal therapies, and simple environmental modifications, your veterinary team can help improve the quality of life of affected cats and help them live comfortably with their owners.
What causes DJD?
The cause in the majority of feline DJD cases remains unknown, Dr. Rodan says, but we do know that obesity is a predisposing factor. Large studies in human medicine have shown that obesity is a cause of DJD and arthritis in people, and the same seems to be true in pets. “We know that weight loss helps with osteoarthritis in dogs, and we have reduction in lameness in cats with weight loss,” says Dr. Rodan.
Another interesting finding, Dr. Rodan says, is the association between chronic kidney disease and DJD. In fact, 69% of cats (between 6 months and 20 years) that have DJD also have chronic kidney disease. “It’s not just coincidence because they’re older cats,” Dr. Rodan says. “There is definitely some correlation.” When veterinarians treat cats with DJD, they need to consider chronic kidney disease when choosing medications, she says.
Injury and genetic conditions—including hip dysplasia, patellar luxation and osteochondrodysplasia—can also predispose cats to developing DJD. Hip dysplasia is prevalent in Maine coon cats, and patellar luxation is common in Abyssinian and Devon rex breeds—although Dr. Rodan says her most recent cases have been in domestic shorthairs. Osteochondrodysplasia in the Scottish fold breed is a dominantly inherited condition that results in malformed limbs and progressive joint destruction. “Deformities can be seen by 7 weeks of age and the condition accelerates degenerative joint disease. There are organizations, especially in other countries, that are recommending that Scottish folds not be bred,” says Dr. Rodan.
Which joints are affected by DJD?
Feline DJD often affects multiple joints in the limbs, spine or both. Spinal or axial DJD is most frequently found between thoracic vertebrae T7 and T10, but more severe disease is seen in the lumbar vertebrae, Dr. Rodan says. Axial DJD increases as the cat ages. (See “‘DJD’ or ‘osteoarthritis’?” below.)
“In the limbs, elbows and knees are affected about 20% each. The incidence in the hips and shoulders is about 18%. And we see it in the hocks as well,” says Dr. Rodan. As opposed to axial DJD, appendicular DJD occurs equally through the various ages. “So, all ages for the limbs; older cats for the back,” concludes Dr. Rodan. Knowing this can help you during your physical examination of a cat you suspect has DJD.
Why is diagnosing DJD a challenge?
Feline DJD is difficult to detect because cats hide their pain as a protective mechanism. Also, just as in people, there’s individual variance in pain threshold among cats, Dr. Rodan says.
“DJD has a slow, insidious onset,” Dr. Rodan says. “Most owners just think their cat is getting old. Plus, pain is not always static. The clinical signs of DJD can wax and wane. Sometimes the cat will have good days; sometimes they’ll have bad days.”
As opposed to dogs, most cats with DJD do not show lameness because the disease tends to impact the same joints bilaterally. “Unless secondary to an injury, owners often don’t recognize signs as cats are not limping because DJD is impacting both legs,” she says.
Dr. Rodan says that in practice, the best way to diagnose DJD is a combination of patient history, physical examination and radiographs.
Patient history and owner observations
Changes in behavior are the most common signs of DJD, but these can also occur with other types of pain, nonpainful illnesses and distress. Clients often recognize the pain of DJD in their own pets more accurately than veterinarians do because they know their cats’ normal behaviors and routines and notice changes. However, clients frequently attribute the changes to old age rather than to pain.
According to Dr. Rodan, signs of pain with DJD can include decreased grooming, reduced movement or withdrawal, changes in vocalization, house soiling, changes in relationships with people or other animals in the household, and human-directed aggression. A cat may exhibit multiple changes in behaviors.
Analysis of a cat’s gait is admittedly challenging to conduct in a practice. So the patient history should include questions about changes in the cat’s mobility, including how high the cat can (and will) jump, whether the cat hesitates before jumping up or down, and whether the client has noticed changes in how the cat climbs up or down stairs.
Dr. Rodan says a good client questionnaire to use is the Feline Musculoskeletal Pain Index (created by Dr. Duncan Lascelles and copyrighted by the Comparative Pain Research Laboratory at North Carolina State University College of Veterinary Medicine). Veterinarians can access the latest index at this NC State link after filling out a brief online form. Although there is a validated feline acute pain scale, there is as yet no validated chronic pain scale in cats.
Your visual and physical examination
The main goal of the examination is to evaluate the cat’s gait and posture, Dr. Rodan says. The first step? Watch from a distance. “Observe them in the exam room,” she says. “They may want to jump up on the bench or the owner’s lap, but they may hesitate quite a while before they jump. They appear to be thinking, ‘Is it worth the pain to get where I want to go?’”
Your hands-on examination should include palpation of the cat’s back and limbs to check for stiffness and muscle atrophy. Dr. Rodan says, “On palpation, we can note a decreased range of motion and joint thickening, but only in the elbows and hocks. In hips, shoulders and knees, DJD has to be really bad before there’s a change in range of motion.” Spinal pain is most common over the lumbar and lumbosacral regions. “Less common findings are pain on range of motion, fluid in the joint capsule, limping and crepitus,” she says.
Finally, observe the cat as it returns to its carrier at the end of the examination, noting any hesitation that might reflect joint pain. As cats should never be forced to get them to move, Dr. Rodan also advises asking clients to take 30- to 45-second videos of their cat jumping up and down from the bed and climbing up and down stairs. If the owner shares the videos with you electronically, you can link them to the pet’s electronic medical records. Comparing these videos over time and to assess response to treatment can be very helpful.
Although many cats have radiographic evidence of DJD, radiographic signs do not necessarily equate with pain. And conversely, DJD pain can be felt before there are obvious changes on radiographs, with a range of 33% to 85% of painful joints having radiographic evidence of disease.3 “Radiographs don’t always correlate with exam findings,” she warns. Therefore, radiographs are taken to rule out other possible causes of pain, such as neoplasia or fracture.
When you’re taking radiographs of these cats, analgesia is essential, Dr. Rodan says. She prefers to do them when the cat is under general anesthesia, such as for a dental prophylaxis or periodontal procedure. Careful radiographic positioning is also important. “Stretching these cats out is going to make them really uncomfortable, but that’s necessary to obtain good views, making analgesia plus sedation or anesthesia critical,” Dr. Rodan says.
If the physical exam and radiographs don’t reveal evidence of DJD but you’re still suspicious that a cat is in pain, you can do an analgesic trial. Ideally you would conduct a nonsteroidal anti-inflammatory drug (NSAID) trial after review of laboratory values.
Treating cats with DJD
Unfortunately, cats with DJD get treated less than dogs. “There are a lot of reasons for that,” says Dr. Rodan. “One is it’s harder to diagnose DJD in cats in the first place. They’re not limping. And then we’re concerned about adverse effects of medications, which is a very important reason.” On top of those factors, owners can have trouble administering the prescribed drugs.
Combination drug therapies and changes to the home environment that allow the cat to perform its normal behaviors are essential to pain management and the patient’s comfort and welfare, according to Dr. Rodan.
Multimodal pharmacologic management
Different medications target different sites along the pain pathways, so Dr. Rodan advocates multimodal therapy. “Use different therapies together because they work synergistically,” she says. “Using them together allows you to use lower doses so you have fewer side effects.”
NSAIDs. Dr. Rodan says the NSAIDs approved for cats—meloxicam and robenacoxib—are the treatment of choice right now for feline DJD, even though they’re not approved in the United States for long-term use in cats. “Meloxicam, which has been around for longer, is approved for long-term use in cats in Canada, Europe, the Middle East, Australia, New Zealand and several other countries,” she says.
When using NSAID therapy in cats, Dr. Rodan advises following the guidelines developed by the International Society of Feline Medicine and the American Association of Feline Practitioners. If you’re going to prescribe meloxicam or robenacoxib for long-term use in the U.S., she recommends asking cat owners to sign a waiver acknowledging the off-label usage.
Use only the 0.5 mg/ml injectable meloxicam and discard the enclosed syringe, replacing it with a 1-ml syringe for accurate dosing to reduce the potential for kidney and liver problems, Dr. Rodan instructs. She advises giving 0.1 mg/kg the first day, then reducing the dose to 0.05 mg/kg every day or less frequently.
“We give the first dose in the practice, then we teach the owner how to give the lower dose at home,” she says. “We mark a tuberculin or insulin syringe with a permanent marker so the owner can see where they’re supposed to draw the drug up to.” Dr. Rodan has her technicians teach clients how to prepare and administer the drug and to explain the importance of accurately administering the drug to the cat.
Dr. Rodan says she often tapers the dose and frequency of meloxicam, and she’s found that many cats are comfortable with low-dose NSAIDs given every other or every third day. “That works because I’m using it in conjunction with something else,” she says.
There are certain precautions to take when combining NSAIDs with other drugs in cats with DJD. Dr. Rodan avoids using NSAIDs with glucocorticoids, warfarin, phenobarbital and digoxin, and she says NSAIDs should also be used carefully with ACE inhibitors and diuretics. “In fact, I will not use NSAIDs with diuretics because it’s so easy for cats to become dehydrated,” she says.
If a cat is on short-term steroids, Dr. Rodan advises a five-day washout period before starting an NSAID. If a cat has been on long-term steroids and you want to attempt to transition it to an NSAID, she says you need to taper the steroid for a minimum of three weeks and then allow for at least a three-week washout period. “I find that most of these cats have been put on long-term steroids because they need them, and I can’t get them off. So I just won’t use NSAIDs in those cases,” she says.
Dr. Rodan says to warn owners about the side effects to look for and advise them to stop the NSAID and call their veterinarian if the cat begins vomiting, refuses to eat or exhibits any other changes. A free downloadable client handout about NSAID use in cats is available here.
Veterinarians are often concerned about NSAID use in cats with concurrent chronic kidney disease, but Dr. Rodan says a number of studies have shown that meloxicam and robenacoxib can be used in cats with concurrent DJD and chronic kidney disease as long as patients are eating well and normovolemic, and the kidney disease is stable and in stages 1, 2 or early stage 3.4,5 Patient monitoring as noted in the AAFP/ISFM’s “Long Term Use of NSAIDs in Cats” is necessary.
Central-acting drugs. About one-quarter of cats with DJD have maladaptive pain, Dr. Rodan notes. “NSAIDs do not work on maladaptive pain,” she says. “So in addition to NSAIDs, or when we cannot use NSAIDs, we have to use something else.”
Although tramadol can decrease central sensitization, Dr. Rodan does not use it. “It’s bitter, and with the [human] opioid addiction problem, I won’t let it be in the clinic,” she says.
Gabapentin is Dr. Rodan’s choice for a centrally acting drug. It can be used for chronic and neuropathic pain without serious side effects. “Gabapentin is fantastic,” she says. “It functions at the site of the spinal cord. It’s short-acting, and it’s ideal when you can use it conjunction with other treatments.” She notes that gabapentin is very safe, though it can be sedating. She starts at lower doses and gradually increases to effect to prevent sedation.
NV-02. NV-02 (also known as frunevetmab) is a feline anti-nerve growth factor monoclonal antibody being developed by Nexvet. There have been two studies published on this emerging therapy,6,7 with a pivotal study in progress. Dr. Rodan says NV-02 appears to be a safe long-term analgesic for cats with DJD-related pain. “Hopefully it’s going to get FDA approval soon,” she says.
Nonpharmacological treatments and environmental modifications
When treating cats with DJD, Dr. Rodan says veterinarians need to consider more than just drugs: Weight reduction in overweight cats, nonpharmacological therapies and environmental changes can all help in DJD cases.
Obesity exacerbates DJD pain because it puts an increased load on the joints, and it causes low-grade inflammation that may be associated with DJD. “Weight loss improves function and mobility; it reduces pain and disability,” Dr. Rodan explains. “Exercise is really important. In fact, in human medicine, they’re now talking about exercise even more than the calories that are eaten.” Dr. Rodan says getting a cat to exercise is as easy as taking it outside on a harness, letting it outside in a safe enclosure, engaging it in interactive and self play, using puzzle feeders, and letting it try hydrotherapy if the cat doesn’t mind water.
The diet the cat eats can help too, Dr. Rodan says: “The only nutraceutical that works is omega-3 fatty acids, and that is when fed in the diet.” Check current prescription joint, kidney and senior diets for omega-3 fatty acid supplementation.
Dr. Rodan has found acupuncture to be a safe, effective therapy for feline DJD when used within a multimodal approach. She has a certified acupuncturist in her practice, and she says cats tolerate the treatments very well.
Other therapies to try in a multimodal management program include the Assisi Loop (or other targeted pulsed electromagnetic field devices) and cold-laser therapy. Dr. Rodan points out that studies in cats are lacking. “These are anecdotal still,” she says, “but I use these treatments in conjunction with other things. I like to use multiple things, and owners don’t mind it. Always reassess the patient to ensure its comfort.”
The home environment should also be modified to allow the cat with DJD to have easy access to its favored places. Dr. Rodan advises clients to provide food, water and litter in easily accessible areas where the cat doesn’t have to compete with housemates. “Owners like to put litterboxes in the basement, but each cat should have access to a litterbox on the floor where it spends most of its time,” she says. “My favorite litterbox for cats with DJD is the dog litterbox for dogs up to 35 lb or a large storage box with an opening cut out in the front. Use whatever box you want as long as the cat can easily get in and out of and have space to turn around.”
A cat with DJD may not be able to crouch down normally to eat or drink from a food or water bowl resting on the floor. “Raising the food and water bowls to about the cat’s shoulder height lets them sit in a more normal feeding posture,” Dr. Rodan says.
Something as simple as a scratching post can be modified for a cat with DJD. Whereas a younger cat might have preferred a vertical sisal rope post, an older cat with DJD may prefer a soft carpet on a horizontal surface.8 Pet steps or ramps can provide easy access to preferred resting areas for cats with DJD.
As with any chronic condition, cats with DJD need recheck appointments to assess how the treatment is working. “Be sure to follow up to see how the cats are doing,” Dr. Rodan says. “Additionally, I like to have videos from before and after treatment. I can see if this cat is really moving around better than in the appointment alone.”
In summary, when looking at the cats in your practice and keeping an eye out for DJD, Dr. Rodan says to be aware that the disease happens in both the limbs and the spine. “Examinations are important; X-rays are important; and history is even more important,” she says. “These cats have a poor quality of life if not treated.”
Once a diagnosis of DJD is reached, NSAIDs should be the mainstay of treatment when indicated, and a multimodal management strategy is best. Your veterinary team’s TLC can provide comfort for cats, despite the presence of DJD, and support for clients who want to be sure their cats are not in pain. “Cats need to be cats. And we want them to have a great quality of life,” Dr. Rodan concludes.
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