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Infected Joint, Septic Arthritis (in Adult)

A septic joint is an one that harbors a life-threatening bacterial infection. Bacteria reach these the joint through traumatic injury (wounds) or can be introduced during joint injection. This is in contrast to the condition in foals, in which bacteria gain access to the joint through the blood stream.

In adult horses, a septic joint usually results from a wound that has penetrated into the joint. Bacteria are introduced into the joint and proliferate. A massive inflammatory process follows. Infection fighting white blood cells rush to the area and begin trying to destroy the bacteria. The products they produce in doing so cause intense inflammation and pain and in themselves damage the joint cartilage.

Horses with a septic joint are severely lame, and usually have a hot and swollen joint. Rapid diagnosis and aggressive treatment is critical to a good outcome.

The most important part of treatment is prompt, aggressive flushing of the joint.

Prognosis & Relevant Factors

Prognosis for a horse with a septic joint is always guarded, meaning that the result could go either way. The longer the time between infection and appropriate treatment, the more joint damage takes place, and the more likely that chronic arthritis (and permanent lameness) will develop.

With time, the infection progressively becomes harder to treat. Bacteria get a stronger and stronger foothold as more of the joint tissues become riddled with infection. Once infection invades underlying bone. and cartilage and underlying bone is damaged, leading to chronic arthritis.

Author: Doug Thal DVM Dipl. ABVP


Steel CM, Pannirselvam RR, Anderson GA. Risk of septic arthritis after intra-articular medication: a study of 16,624 injections in Thoroughbred racehorses. Aust Vet J 2013;91(7):268-73.


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