Osteoarthritis is under recognised in cats. Studies show that 60–90% cats have radiographic evidence of arthritis but it's actually pretty rare for a cat to be presented to us for an arthritis assessment.
Cats are masters of hiding pain. So here we're going to look at how to get around this and help our arthritic cats.
What is osteoarthritis?
Put 'osteo' (bone), 'arthro' (joint) and 'itis' (inflammation) together and you get osteoarthritis (OA), a term that describes a form of chronic joint inflammation caused by deterioration of joint cartilage and the underlying bone. Because of this, it's often also called degenerative joint disease (DJD).
Mostly, we just call it arthritis.
There are two main types of OA: primary, which has no underlying cause (rare in dogs, possibly common in cats); and secondary, which occurs because of something else such as abnormal wear on normal cartilage.
What causes osteoarthritis?
In cats, the main causes of OA are:
- wear and tear (ie primary arthritis)
- dislocation of the kneecap (patella luxation)
- abnormal development of the hip (hip dysplasia)
- cartilage abnormalities (seen in Scottish Folds)
There are several factors that increase the risk of developing arthritis. Genetics play a big role, for example, conditions such as hip dysplasia and patella luxation occur much more commonly in certain breeds. Obesity is another risk factor as it places more stress on joints.
Medical conditions and treatments that affect collagen or cartilage also increase the risk of arthritis. These include diabetes and prolonged treatment with corticosteroids.
What are the signs of osteoarthritis?
We often think that OA = lameness. In dogs, this is mostly true but lameness in cats tends to be less obvious. Instead, you need to look out for clues suggesting of arthritis such as:
- reluctance, hesitance or refusal to jump up or down
- jumping up to lower surfaces than previously
- difficulty going up or down stairs
- stiffness in the legs, especially after sleeping or resting for a while
- difficulty using the litter tray
- difficulty going through the cat flap
- increased irritability and grumpiness
- reduced activity level
- reduced frequency or time spent grooming
Because arthritis often goes undetected in cats, International Cat Care and the International Society of Feline Medicine (ISFM) have produced a 'mobility checklist' that you can download from here and use to see if there have been any changes in your cat that may be indicative of arthritis or joint pain.
How is arthritis diagnosed?
Arthritis is mainly diagnosed on history and physical examination. In the history, we're looking at age, signs (as above) and previous reports of injury/trauma.
On physical examination, we're looking for:
- visible joint deformity
- joint pain
- decreased range of motion of the affected joint
- grating detected with joint movement (known as crepitus)
- increased fluid in the joint (effusion)
- thickened joint capsule
- joint instability
We make suggest taking some X-rays. These help rule of other causes of joint pain and assess the degree of bony changes in the joint. It should be noted that the severity of changes on X-ray doesn't necessarily match the severity of clinical disease. We may see lots of degenerative change on X-ray but have a cat that's walking around pretty well.
Blood and urine tests are not usually needed to diagnose or investigate arthritis. But we may recommend them if we're concerned about other conditions (eg diabetes) or to check for contraindications before starting medications.
How is arthritis treated?
The goal of OA treatment is to alleviate pain and improve (or maintain) function. There is no cure. We may have to try several different treatments to find what works for your pet. Usually, we'll end up doing a combination of the following.
This is about keeping your cat comfortable and encouraging the sort of activity that helps with mobility but doesn't cause pain. Things you can try include:
- providing a warm, soft bed in a spot that's easy for your cat to get to – covered ('igloo style') beds tend to be popular with most cats
- providing a ramp or some 'steps' up to favourite positions like the windowsill or couch
- having a litter tray with at least one low side for easy access
- making sure everything your cat needs is on one level if you live in a multistory property
- grooming and cleaning your cat – soft brushes may be better tolerated than metal ones; a damp microfibre cloth can be pretty good at mimicking a cat's tongue
- clipping claws regularly as arthritic cats tend not to do much scratching
If your cat is overweight, try and get some weight off to reduce stress on joints. It's not always easy to get a cat to lose weight safely. Changing diets suddenly can make cats stop eating – something we don't want. The best approach may be to feed more wet food than dry (it has fewer calories) and/or to use one of the lower carb style diets such as Royal Canin® Satiety or Hill's® Metabolic.
There are also special 'joint diets' such as Hill's® J/D. This contains supplements that may reduce inflammation and support/protect joint cartilage. Most supplements can be purchased separately if preferred.
There are lots available – very few have scientific evidence of benefit in cats. Here are some that do have some evidence in other species (mostly dogs and people) and may help cats too:
- omega 3 fatty acids found in fish oils (docosahexaenoic acid or DHA and eicosapentaenoic acid or EPA) – these have been found to reduce production of inflammatory chemicals and help with the symptoms of OA in dogs. Their evidence of benefit in people with OA is less clear, but they do seem to help relieve symptoms of rheumatoid arthritis
- green-lipped mussels – there are several products containing green-lipped mussel extracts that have been around for a while but a newer product called Antinol® appears to have some pretty impressive evidence of benefit. It's a dog medication but can be safely used in cats – and for once, it's something they seem to like!
- chondroitin sulphate and glucosamine (glucosaminoglycans) – are widely used to slow down the progression of arthritis and protect joint cartilage in people and pets. There is some evidence that they work, but not all products are equal and it can be hard to know if you're getting a high-quality version when it comes to pet products
- methylsulfonylmethane (MSM) – this seems to have a positive effect in people with OA (when used in combination with other things), but there isn't much in the way of good evidence in cats
There are several supplement blends available for cats. Their effectiveness is unclear: some people swear they help; some people don't notice much change with their use. They don't appear to cause harm and it's possible that even if you're not seeing things improving, perhaps things aren't progressing either.
Injectable joint protectants
These are also glycosaminoglycans like chondroitin sulphate and glucosamine. The most common one used is pentosan, which comes in several different formulations by different companies. We use one called Zydax® because it has the highest quality evidence. It is given as a course of four injections over 4 weeks. Note that its use in cats is 'off-label'.
Non-steroidal anti-inflammatory drugs (NSAIDs)
NSAIDs are the most commonly used pain-relieving medications. The main one used in cats is meloxicam (there are very few NSAIDs licenced for cats in Australia. These drugs are metabolised and excreted by the liver and kidneys, which may be compromised in older cats, so before we start NSAIDs or if we're using them long term, we may recommend blood and urine testing.
The ISFM and AAFP (American Association of Feline Practitioners) have put together an NSAID information leaflet that you may find helpful. It can be downloaded here.
Other pain-relieving medication
In addition to or in place of NSAIDs, we may prescribe pain-relieving medications such as tramadol and gabapentin. In some cases, we may use an oral opioid medication (buprenorphine).
Studies in cats are lacking, but acupuncture has shown to be effective in other species. People often ask how well cats tolerate 'the needles'. The answer is 'surprisingly well' but laser acupuncture is often used instead of needles in cats. It tends to be used in conjunction with other therapies rather than as a replacement.
While people often have joint replacement surgery for arthritis, we rarely perform it in cats. When we do, it's usually to fix the underlying cause of OA such as patella luxation.