Osteoarthritis in cats
diagnosis and treatment
It is well recognised that as humans get older they are likely to suffer
from joint pain caused by osteoarthritis. It is also well known that older
dogs suffer from joint discomfort and vets are familiar with the
medication dispensed to relieve their pain. However until recently,
feline osteoarthritis (OA) has not been commonly diagnosed or treated
mainly due to the cats' survival instinct to hide signs of pain and the
lack of recognition of the condition by owners and veterinary surgeons.
Incidence of osteoarthritis in cats
Due to the challenges of diagnosing arthritis in cats, it can be difficult to
tell how many cats are affected. However, recent studies looking at
radiographs of older cats produced startling results. Ninety per cent of
cats over 12 had evidence of degenerative joint disease (Hardie et al,
2002). This study and others suggest that osteoarthritis is very
common in older cats and therefore is being under-diagnosed.
What causes osteoarthritis?
Osteoarthritis is a type of arthritis in which the normal cartilage that
cushions the joint is worn away, exposing the bone and resulting in
discomfort. OA can be primary or secondary to a joint injury or
abnormality as described below. Primary OA occurs in previously normal
joints that have not suffered a specific injury and is the most common
form seen in older cat, the cause of which is not clearly understood.
There are some factors that can contribute to the development of OA.
These include:
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Genetics: certain breeds appear to be predisposed to developing
arthritis due to various underlying joint problems, for example
hip dysplasia in Maine Coons and patella luxation in the
Abyssinian. Scottish Folds are particularly prone to OA affecting
multiple joints and Burmese cats are thought to suffer with
elbow arthritis more than other breeds
Injury causing abnormal joint loading: fractures, dislocations and
other injuries can cause the joint to be used differently and
result in secondary OA of the affected joint
Obesity: obesity does not cause arthritis but it will exacerbate
the condition
Acromegaly: this unusual hormonal disease results in diabetes
mellitus and some cats also develop arthritic joints
What are the signs of osteoarthritis?
The most obvious sign of arthritis is joint pain, with the most commonly
affected joints being the elbows, stifles (knees) and hips. However, this
is where the problem arises; cats are the masters of hiding discomfort
and do not demonstrate the obvious signs of pain. They are not taken
for walks like dogs and restrict their own activity to minimise the use of
the sore joints. They also tend not to show the same obvious signs of
pain as other species (e.g. vocalising), exhibiting more 'passive'
behaviour to disguise pain.
Signs of pain in cats that owners may observe and report to the vet
include the following:
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Reduced mobility
o Reluctance to jump up or down from furniture
o Sleeping in different, easier to access sites
o Difficulty using the cat flap
o Lameness or stiff/stilted gait – this is relatively uncommon
as often multiple joints are affected and so the lameness
is disguised
o Litter tray accidents, missing the tray, reluctance to climb
into high sided trays
Changes in grooming behaviour
o Matted and scurfy coat
o Overgrooming painful joints
Temperament changes
o Reduced interaction, eg, lack of response to petting
o Lack of tolerance of handling, children, other pets
Changes in activity level
o Playing and going outside less frequently
o Not hunting or exploring the outdoor environment as
frequently
o Overgrown claws due to lack of activity
On examination affected cats may
demonstrate discomfort and resist
palpation and movement of the affected joints. The joints may feel firm
and swollen. Orthopaedic examination can be challenging in cats, as
they are often reluctant to walk normally in a consulting room. Using
'Cat Friendly Practice' principles and not rushing will help the cat relax
and behave more normally, facilitating a more rewarding examination.
The next step in the diagnosis involves radiography (figure 1). Ideally
two views are taken of the affected joints and changes include the
formation of new bone around the joint margins (the bodies attempt to
‘stabilise’ the joint). Sclerosis (thickening) of the underlying bone and
narrowing of the joint space are also observed. Further laboratory tests
are not usually required to diagnose osteoarthritis, however as affected
cats tend to be older and may have more than one disease (see later),
a full investigation should be performed before prescribing medication.
Management of the arthritic cat
Treating arthritis in cats doesn't start and finish with a pill or potion.
Home comforts and management adjustments are vital to the
improving the cats' quality of life and can be just as important as
medications.
Easy home and management adjustments for the arthritic cat
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Provide soft beds for sore joints in easily accessible, quiet places
(figure 2)
Place beds in quiet, draft free areas of the house
Igloo beds or cardboard boxes can make an older cat feel warm
and secure
Provide 'steps' up to higher sites, eg, the sofa, the cat flap
Tie the cat flap open so the cat doesn’t need to push through
Always have a litter tray inside and use a low sided version or
cut out the sides to make it easy for arthritic cats to climb in
Use different types of litter that are softer for sore feet
Make sure food and water are easily accessible, at floor level or
with steps up to higher levels
Put food, water and litter trays on one level to avoid the cat
having to go up and down stairs
Radiator beds are popular but again arthritic cats will need help
to get into them, other warming devices such as wheat bags can
help but electrical devices should be used only when the cat is
monitored
Arthritic cats may need extra grooming and help cleaning eyes
and perineal region
Overgrown claws need regular cutting.
Nutritional management and nutraceuticals
Obesity will exacerbate OA and so should be avoided. Obese cats need
careful diet changes supervised by a veterinary surgeon. Overweight
cats need to lose weight slowly and changes may take several months.
Rapid weight loss can result in metabolic problems such as hepatic
lipidosis when a large amount of fat accumulates in the liver.
Several dietary supplements and diets are available for cats with OA
containing combinations of essential fatty acids (EFAs) (to reduce
inflammation), natural glycosaminoglycans (to help improve cartilage
quality), anti-oxidants (reduced free-radical damage), methionine,
manganese and selenium (to assist cartilage synthesis) (Hills j/d).
Nutraceuticals
Chondroitin and glucosamine supplements are available for cats. The
affects are unproven but they have been shown to be effective in dogs,
horses and people and so may be beneficial. They may help in early or
mild cases but are not likely to be enough alone in more severe cases.
Medical treatment
Medications can be very effective at controlling pain but should only be
used once the cat has been fully assessed for their general health and
the presence of other diseases. Most cats with arthritis are geriatric and
so commonly suffer concurrent disease. Ideally cats should have a full
biochemistry profile (to check liver and kidney function), haematology
(red and white blood cell counts), and urinalysis. If this is cost
prohibitive the minimum database should include a biochemistry profile
and urinalysis, specifically specific gravity (concentrating ability).
The most common medication used and the only medication to have a
license for the treatment of chronic pain caused by OA in cats is
meloxicam (Metacam; Boehringer-Ingelheim). This drug is very
effective for treating pain but should be avoided in cats with kidney
problems, liver problems, vomiting/diarrhoea or any cat that is
dehydrated or has low blood pressure (hypotension). The lowest
effective dose should be used and the drug is ideally given with food.
Maximising water intake is important in all older cats (to prevent
dehydration and urinary problems) and this is especially true of cats
receiving meloxicam (water fountains, wet food diet etc).
Alternative drugs have been used including opioids (buprenorphine
which can be given sublingually, tramadol) and gabapentin. These
drugs are not licensed for use in cats with osteoarthritis and so have
not been closely studied. Anecdotal reports suggest they may be useful
in cases where meloxicam in not appropriate. Corticosteroids are not
recommended as they cause side effects and can result in long term
health problems such as diabetes.
Alternative treatments
Acupuncture has been used in other species to treat the chronic pain of
OA. This treatment has not been proven in controlled studies but
anecdotal reports suggest it could be useful for some cats. It should
always be performed by a specially trained veterinary surgeon and not
used as a substitute for medication in severe cases.
In conclusion OA is common in older cats and is challenging to identify.
Diagnosis relies on an observant owner and a veterinary surgeon asking
the right questions and using cat friendly practice principles when
approaching the examination and management. Medications can be
very effective and improve a cat’s quality of life but concurrent geriatric
disease should be considered before such drugs are prescribed. The
importance of management changes cannot be over-estimated.