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 cats, the cause of which is not clearly understood.

There are some factors that can contribute to the development of OA. These include:

• 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 (such as 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:

Reduced mobility

• Reluctance to jump up or down from furniture.
• Sleeping in different, easier to access sites.
• Difficulty using the cat flap.
• Lameness or stiff/stilted gait - this is relatively uncommon as often multiple joints are affected and so the lameness is disguised.
• Litter tray accidents, missing the tray, reluctance to climb into high-sided trays.

Changes in grooming behaviour

• Matted and scurfy coat.
• Overgrooming painful joints.

Temperament changes

• Reduced interaction, for example,?lack of response to petting.
• Lack of tolerance of handling, children, other pets.

Changes in activity level

• Playing and going outside less frequently.
• Not hunting or exploring the outdoor environment as frequently.
• 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. 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, 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

• Provide soft beds for sore joints in easily accessible, quiet places.
• 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 like the sofa or 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 results?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, particularly specific gravity (concentrating ability).

The most common medication used and the only medication to have a licence 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.