What is septic arthritis?
Septic arthritis is an infection of one or more joints that occurs when bacteria or another infectious agent is introduced into the joint(s), leading to painful inflammation. The infection most commonly occurs through injury to a joint like a penetrating wound but can also be spread through the bloodstream or from the surrounding tissues. In general, male, large and giant breed dogs are most affected. Septic arthritis is seen most often in dogs 3 months to 11 years of age, but dogs of any age can develop it.
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 affected 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), 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 dog’s blood will be taken to look for evidence of infection and inflammation. Arthrocentesis (sampling joint fluid) will also be performed, and the fluid will be assessed for the presence of inflammatory cells, and cultured to determine what infectious agent is present. X-rays of the affected joint may also be performed to assess for potential damage in the area.
Are there any specific risk factors that set the stage for septic arthritis?
There are some factors that can make a dog more vulnerable to septic arthritis. For example:
- Diseases that suppress the immune system, such as diabetes mellitus and Addison's disease.
- Medications that suppress the immune system.
- Trauma that penetrates a joint (bite wound, gunshot, migrating foreign body like a grass awn).
- Surgery involving a joint.
- Osteoarthritis, other joint damage, or injections into a joint.
How is septic arthritis treated?
If your dog has septic arthritis and is very ill, they will be hospitalized and treated as necessary to be stable. Your veterinarian will extract joint fluid for bacterial culture and may lavage (flush) the joint to minimize joint damage. Some dogs 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.
Once home, these dogs benefit from long-term management. Cold packs, alternated with heat packs, may help to increase blood flow and decrease 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 an antibiotic is chosen, the medication is typically given until at least 2 weeks after clinical signs have resolved; this means treatment can continue for at least 6 to 8 weeks. In addition, a non-steroidal anti-inflammatory drug (NSAID) or an opioid may be given to relieve pain and inflammation.
What follow-up care might be needed?
It will be important to watch for joint pain and swelling to return. There may be a need for microscopic evaluation of joint fluid to monitor response to therapy. Physical rehabilitation 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.
