Joint Cartilage Erosion in Cats

Erosive, Immune-Mediated Polyarthritis in Cats

Erosive, immune-mediated polyarthritis is an immune-mediated inflammatory disease of the joints, in which the cartilage of the cat's joint (articular cartilage) is eroded away.

Leukocyte cells, leukocyte enzymes (catalyzing reactions), cell-mediated immunity, immune complexes (an antibody bound to its triggering antigen), and autoallergic reactions are all directed against cartilage components. This leads to an inflammatory response by the tissue surrounding the cartilage, and protein activation (complement) in response to the immunity displaying cells.

Destructive enzymes, which are released from inflammatory cells, damage the articular cartilage, synoviocytes (cells which produce a lubricating fluid, called synovia, for the joints), and chondrocytes (cartilage cells), leading to erosive changes in the joints.

The condition or disease described in this medical article can affect both dogs and cats. If you would like to learn more about how this disease affects dogs, please visit this page in the PetMD health library.

Symptoms and Types

Symptoms for cats are often cyclic, coming and going at random intervals. These symptoms include:

• Lameness (ocassionally shifting-leg lameness)
• Stiffness in walk
• Decreased range of motion
• Cracking of the joints
• Joint swelling and pain in one or more joints
• Joint instability, subluxation, and luxation

The typical onset of immune-mediated erosive polyarthritis in cats is from one to five years of age and the most common type of the disease is feline chronic progressive polyarthritis (FCCP).

Causes

The suspected causes for this form of joint cartillage erosion are T lymphocyte effector cells that carry out the attack response, and an abnormal antigenic response to the host antibody. That is, an immune response to a substance that stimulates production of antibodies, an antigen, which acts as a “trigger.” Other known causes include:

• Idiopathic
• Feline leukemia virus (FeLV) and feline syncytium-forming virus (FSFV) -- both of which have been linked to cats with feline chronic progressive polyarthritis (FCPP)

Diagnosis

You will need to give your veterinarian a thorough history of your cat's health leading up to the onset of symptoms. Your veterinarian will perform a thorough physical exam on your cat, taking note of signs of pain, decreased range of motion, and any lameness.

A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, a urinalysis, and an electrolyte panel. Joint fluid aspirate will be taken for lab analysis, and submitted for bacterial culture and sensitivity. A biopsy of synovial tissue will also help to make a definitive diagnosis.

X-ray images can also be used as a diagnostic tool. If an erosive, immune-mediated polyarthritis condition is present, it will be visible on the radiograph image.

Treatment

Physical therapy, including range-of-motion exercises, massage, and swimming can help treat severe disease. Bandages and/or splints may be placed around the joint to prevent further degradation of the cartilage, especially in cats that are experiencing difficulty walking. Weight loss also helps decrease pressure on the joints if the cat is overweight.

Surgery for this condition is generally not recommended. However, total hip replacements, and femoral head ostectomy (surgical removal of part of the thigh bone) may be considered.

Arthrodesis of the carpus (wrist) is generally quite successful for treating joint pain and instability. Arthrodesis of the shoulder, elbow, stifle (knee), or hock (ankle), meanwhile, is not as reliable at yielding positive results.

Living and Management

Your veterinarian will schedule frequent follow-up appointments to examine your cat's progress. If your cat’s condition continues to worsen, you must contact your veterinarian immediately for care.