This article will concentrate principally on the degenerative arthritis called osteoarthritis. Compared to the dog and human, cats are fortunate to suffer relatively infrequently from osteoarthritis although it is still the most common long term manifestation lameness in the cat.

OSTEOARTHRITIS

Osteoarthritis is a non-inflammatory, often inherent condition of movable joints that result in changes to the cartilage surfaces and their surrounding tissues with cartilage erosion and new depositions of bone to develop changed and irregular surfaces leading to joint pain, stiffness, swelling and limitation in movement with deterioration with age.

How does it occur?

There is little doubt that certain breeds have an inherited predisposition to osteoarthritis. This is known as primary osteoarthritis and conditions such as hip dysplasia in the Burmese cat would be a good example. Questioning breeders on whether arthritis has been known in their breed lines prior to purchase of a pedigree cat may be sensible. 'Moggies' far less frequently develop inherited osteoarthritic conditions.

Secondary osteoarthritis is more common and arises from some insult of the joint such as the trauma of a road traffic accident, abnormal stresses on the joint surfaces or infection in a joint.

How do you diagnose it?

Your vet will help to diagnose the condition and also eliminate other causes of joint disease. Radiographs may be necessary, as may analysis of joint fluid (the latter to largely eliminate other reasons for joint damage).

Treatment

The secret of successful treatment is early diagnosis and careful management. Treatment can be divided into three areas:

• Weight control. Fat cats have to carry the extra weight!

• Encourage exercise. Don't let fat cat sleep on the couch all day!

• Surgical. Only suitable for specific cases where other solutions have proven ineffective. An example would be where severe arthritis of the hip may respond to surgery.

• Medication. This is a vast topic and depends on the individual case, the severity of problem and owner compliance! It can be divided into conventional and non-conventional therapy

Non-conventional therapy:

• Copper collars and magnetic field therapy (magnets in collars).

• Rhus tox, homeopathic remedy for use in conditions where exercise alleviates stiffness. Bryonia where there is increasing pain with exercise.

• Seaweed extracts, cider vinegar, Devil’s Claw.

• Nutropharmaceutical extracts containing chondroitin and glucosamine associated with manganese salts. This group of natural products, extracted from a range of animals from shark fin to cockerel comb has some scientific support to suggest benefits to joint function so long as the disease is not too far advanced.

Conventional therapy:

This is largely divided into four groups:

• Use of NSAIDs (non steroidal anti inflammatory and pain relief drugs) Very few are licensed for use in the cat and none for long term use due to potential toxic effects.. However there is considerable data available and where obvious suffering is occurring and there is no obvious alternative your vet may discuss the judicial use of these drugs. If this is advised that occasionally they can cause stomach upsets and should be discontinued if vomiting, diarrhoea or loss of appetite occur. They should be used under very careful veterinary supervision if there is any suggestion of blood disorder, kidney, liver, heart disease or gastro-intestinal ulceration. Drug interactions can occur (e.g. with steroids). Given short term by injection but more normally by the oral route, with food.

• Polysulphated glycosaminoglycans (PSGAGs) have anti-inflammatory activity and help modulate cartilage and synovial membrane metabolism. Usually given as weekly injections for a month and then every few months. Again this product is not licensed for use in cats in the UK.

• Hyaluronic acid derivatives have similar functions to B but at present none are licensed on the UK market.

• Steroids can be used to suppress inflammatory changes on the joint surface but should only be used where there is inflammatory erosive osteoarthritis present.

TRAUMATIC ARTHRITIS

This is a generalised term for changes to a joint resulting from either a single or repetitive trauma to that joint.

Acute traumatic arthritis

• Acute trauma to a joint may manifest as a sudden onset lameness with swelling, heat and pain and warrants early veterinary attention . It is important to differentiate this type of acute joint pain from other conditions such as septic or infected arthritis. Early assessment and treatment can reduce the long term damage to the joint. In this condition there is disruption of the cartilage, bone, synovial membranes and ligaments supporting the joint. Inflammatory changes lead to increased synovial (joint) fluid production with swelling and associated discomfort.

• Disruptive, traumatic, acute, conditions with bone damage, dislocation and ligamental rupture may require surgical intervention but only after stabilisation of firstly the patient and secondly the joint itself. Several weeks of resting of the joint is important with possible immobilisation, depending on the condition may be necessary, including and followed by use of non-steroidal anti-inflammatory and pain killing drugs (NSAIDs). Prognosis has to be guarded in many conditions and a degree of osteoathritis will develop in many cases.

• Non-disruptive, traumatic, acute, conditions will not require surgery. Rapid treatment with immobilisation / rest and the use of NSAIDs will provide good results in many cases although in severe cases osteoarthritis will result.

• Repeat trauma induced arthritis occurs when A. there is poor conformation or B. the activity of the animal lends to this occurring. In the former case it is often difficult to deal with although careful and regular assessment of the growing animal can limit problems in this area. In the latter case, identifying the causative action before severe damage is caused and eliminating it will help.

INFLAMMATORY ARTHROPATHIES

Infective arthritis

Depending on the source of infection and the organism causing the infection this condition can manifest as either acute lameness or a grumbling sore joint. Prompt and efficient treatment is required as misdiagnosis or the wrong treatment can lead to permanent incapacitation, with joint degradation and sometimes, generalised disease.

Infection of the joint can be by two routes:

• Direct penetration of the joint; a bite, thorn or road accident.

• Spread via the blood supply.

The organisms involved are varied and depend on route of infection Common organisms are B-haemolytic streptococci, Staphylococci, haemolytic E.coli, Erysipelothrix, and Corynebacterium. Less commonly it has been known for fungal arthritis to develop. The Pet travel scheme may open the borders for the importation of diseases from abroad.

The most common cause of an infected joint, from our experience, is a wound from a cat bite and this presents with varying degrees of lameness with a hot, swollen joint or joints with pain on palpation or manipulation. There may be swelling of the limb and generalised signs such as raised temperature and enlarged lymph nodes and even multi-organ failure.

Radiographs should be taken, as much as to rule out other causes of joint damage as to provide a diagnosis and a sterile sample of joint fluid should be taken for bacterial culture, antibiotic sensitivity and microscopic examination. Blood haematology can sometimes be useful when there are signs of generalised disease.

Treatment with antibiotics specific to the bacterial organism over several weeks is required in all cases. In severe cases, joint drainage and lavage, sometimes over a considerable period of time is required. Pain and anti-inflammatory relief may be required using NSAIDs.

Arthritis induced by Foreign Bodies

This should always be checked for and eliminated when a single joint painful arthritis occurs, especially if there is evidence of a penetrating wound. Shot pellets, blackthorn, wood splinters and glass shards are all common foreign bodies and not all of them show radiographically!

Immune Based Arthritis

A small and important group of diseases causing inflammatory arthritis. Normally several joints (they are usually polyarthritic diseases) are involved with marked inflammation of the synovial membranes, joint swelling, often with pain and sometimes temperature rise. We quite often find that these cases respond poorly to the use of drugs used for other forms of arthritis such as the non-steroidal anti-inflammatory/analgesic drugs (NSAIDs). The pathology of these diseases is the production of ‘immune complexes’, produced, depending on disease type, either locally in the joint or systemically (throughout the body system. These immune complexes stimulate a type 111 hypersensitivity reaction which produces the clinical symptoms. The underlying cause for these diseases is unknown.

Diagnosis can be difficult, partly due to the rarity of some of the disease forms. Certain diseases have specific tests to help identify them but a general test that can help direct your vet towards a diagnosis is a joint fluid sample that is negative for bacterial and fungal culture, joint fluid analysis reveals a high white blood cell count with a particularly high count of a white cell called a neutrophil.

They can be divided into erosive and non-erosive types, depending on whether destruction of the cartilage and bony surface occurs.

Erosive conditions include:

Reiters disease

This is also known as periosteal proliferative polyarthritis is relatively common in the cat, affecting the carpi (wrist) and tarsi (ankle) of the cat with laying down of new bone on the surface and beyond the confines of the joint. Inflammation of the joint membranes (synoviae) causes joint swelling and new bone is layed down at the attachment of tendons and ligaments around the joint making these structures susceptible to rupture. Cats are presented to the vet often once the condition is well established. Treatment is usually with prednisolone corticosteroid although this can be used in combination with certain cytotoxic drugs.

Non-erosive conditions include:

Systemic Lupus Erythematosus

As the name suggests this condition affects the whole body and can take on many different manifestations. This article will only touch on this condition but can be associated with autoimmune haemolytic anaemia, kidney disease, skin and gum eruptions, central nervous system disease, other blood disorders as well as polyarthritis (multiple joint disease). Again, the causative agents are unknown but there is evidence of an unknown, underlying viral infection which stimulates an abnormal ‘whole body’ response with immune complex hypersensitivity developing against a wide range of body cells and tissues. Clinically the polyarthritic form shows as a symmetrical multi-joint lameness usually with temperature rise, lymph node enlargement loss of appetite, mobility and muscle pain and wastage. Radiographs show little evidence of bone change. Blood testing for antinuclear antibodies (ANA test) if positive with clinical symptoms is a useful indicator of disease. Prognosis with treatment is always guarded, the disease usually being progressive leading to organ failure. Corticosteroids in combination with other cytotoxic drugs such as azothiaprim and cyclophosphamide are often used.

Idiopathic polyarthritis

This group are all the inflammatory diseases causing arthritis where no common feature or cause can be found. They can be divided into four groups but have few common denominators. Causative factors can be neoplasia (cancer), gastrointestinal disease, infections elsewhere in the body and other types of immune complex disease. What this indicates, is that if arthritis occurs along with other disease problems, there may be a link between them. An open mind must be maintained!

Drug Induced Arthritis

Polyarthritis, lymph node enlargement, inflammation of blood vessels leading to skin rashes have been reported after the use of several antibiotics such as the sulpha drugs, cephalosporins, macrolides, and penicillins. Withdrawal of the drugs usually leads to reversion to normal health. There have been reports of polyarthritis after vaccination usually clearing within a few days of the reaction. It must be emphasised that these reactions are rare and are far outweighed by the benefits of treatment or vaccination for the majority.