Septic Arthritis in Cats

By Tammy Hunter, DVM; Robin Downing, DVM, DAAPM, DACVSMR, CVPP, CRPP

My cat was diagnosed with septic arthritis. What is this?

Septic arthritis occurs when bacteria or another infectious agent is introduced into one (or more) joints, leading to painful inflammation. Dogs are more commonly affected, but the condition can occur in cats, although it is rare.

What are the signs of septic arthritis?

The signs of septic arthritis include heat, swelling, and pain in one or more joints. There will typically be decreased range of motion in the affects joint(s), as well as fever, lethargy, and lack of appetite.

What kinds of infectious agents cause septic arthritis?

Bacteria that can live and grow in the presence of oxygen (aerobic bacteria) and bacteria that can live and grow in the absence of oxygen (anaerobic bacteria), and fungal organisms can all cause septic arthritis.

If septic arthritis is suspected, your cat’s blood will be taken to look for evidence infection and inflammation. Arthrocentesis (sampling joint fluid) will also be performed, and the fluid will be assessed for the presence of inflammatory cells, as well as cultured to determine what infectious agent is present.

Are there any specific risk factors that set the stage for septic arthritis?

Any trauma that penetrates a joint, or a surgery involving a joint, can result in septic arthritis. Osteoarthritis, other joint damage, or injections into a joint can also be root causes of septic arthritis. Some diseases, such as diabetes mellitus, suppress the immune system, which can create a predisposition to infection. Medications that suppress the immune system can also influence the development of septic arthritis.

How is septic arthritis treated?

If your cat has septic arthritis and is very ill, they will be hospitalized and treated as necessary to become stabilized. Your veterinarian will extract joint fluid for bacterial culture and may lavage (flush) the joint to minimize joint damage. Some cats with septic arthritis require surgical opening of the joint, removal of abnormal tissue, and copious lavage. Occasionally, a flushing catheter may be placed to provide access to the joint for post-operative flushing.

"Activity should be restricted until cleared by your veterinarian."

Once home, these cats benefit from long-term management. Cold packs alternated with heat packs may be beneficial for increasing blood flow, and decreasing inflammation and swelling. Activity should be restricted until cleared by your veterinarian.

Your veterinarian may prescribe a broad-spectrum antibiotic while waiting for the results of the bacterial culture and sensitivity panel. Once the best choice of antibiotic is made, the medication will typically be given for at least 4 to 8 weeks. In addition, a non-steroidal anti-inflammatory drug (NSAID) or a narcotic may be given to relieve pain and inflammation.

What follow-up care might be needed for my cat?

It will be important to watch for the return of joint pain and swelling. There may be a need for microscopic evaluations of joint fluid to monitor response to therapy. Physical rehabilitation techniques may speed healing and help prevent joint degeneration.

Be aware of the potential for degenerative joint disease, recurring infection, limited range of motion in the affected joint(s), bone infection, or generalized infection that spreads to other areas of the body from the infected joint.

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