As a general rule, the bones of the mammal's skeleton are held together by ligaments & the moving parts of the bone are covered with a glass-like articular cartilage to ensure smooth movement. The moving parts are supported in a sac called the joint capsule, which contains an oil-like compound called synovial fluid. This protects & supports the ligaments & cartilage.

Diseases of the joint may lead to damage of the articular cartilage, disturbance of the joint fluid or weakening of the ligaments between the two bones. Such changes destabilise the moving parts & interfere with the correct movement of the bones. When this happens, the body reacts to overcome the instability & this inflammatory reaction is called arthritis.

The early stages of this reaction are referred to as acute arthritis & the changes seen are as follows:

•    soft swelling of the joint, painful to the touch

•    pain associated with movement of the joint

•    heat localised to the area of the joint

Where the underlying cause of acute arthritis is not treated & when the diseased joint is not rested, the acute reaction is likely to progress to chronic arthritis. As time progresses, the body attempts to stabilise the joint by transforming the fibrous ligament bridges into bone. This process, often referred to as osteoarthritis, restricts the natural movement of the bones & predisposes to further attacks of painfull acute arthritis.

Changes associated with chronic arthritis include:

•    hard, painless swelling associated with the bone on either side of the joint

•    restricted movement of the joint with some discomfort

•    crepitus ( cracking sound ) during movement of the joint

Eventually as chronic arthritis progresses, the two bones will fuse, a process called ankylosis. No further arthritic reaction then occurs, but under such circumstances no movement of the joint is possible.

When an animal presents at the surgery with leg lameness or pain associated with the spine, it is important to determine the cause.Treatment is administered to both take away discomfort & minimise the development of chronic osteoarthritis. Techniques used in veterinary medicine to investigate arthritis include the following:

•    clinical examination with digital manipulation of the joint

•    radiography

•    aspiration ( removal by needle & syringe ) of joint fluid for laboratory analysis

•    surgical biopsy of the cartilage, bone & soft tissues involved in the joint structure

•    ultrasound

•    blood haematology & serology

Treatment of arthritis is variable & dependent upon the nature of presentation & the underlying cause, but may include one the following:

•    surgical repair or stabilisation

•    antibiotics to overcome septic arthritis

•    steroid therapy to treat autoimmune arthritis, eg rheumatoid arthritis in dogs

•    non-steroidal antiinflammatory therapy

•    glucosamine & chondroitin supplementation to reduce arthritic progression

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