Lameness after synovial sepsis

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Synovial sepsis is a relatively common condition affecting horses and causes acute lameness and pain. It is a serious condition and prompt, aggressive and early treatment is associated with better outcome. Bacterial synovial infection causes a severe inflammatory reaction in the synovial environment, and this process can trigger degenerative changes. Even with acute aggressive treatment, eradication of the infection may be challenging in some cases. Some cases may develop protracted synovial infection with chronic lameness. In other cases, involvement of tendinous or osteochondral components may cause persistent lameness.

Unfortunately, the clinician may face the scenario when a horse shows lameness after treatment of a synovial infection and the question to answer is: Is the infection eradicated? Or is the infection persistent?

As clinicians, we strongly rely on synovial fluid analysis. Bacterial culture is considered the gold standard for diagnosis of synovial sepsis; however, it is considered that only about 35-45% of those cases with suspected synovial infections may yield a positive bacterial culture. Cytology of the synovial fluid is also used to guide our decisions; however, any intrasynovial intervention, being synoviocentesis, needle flush, surgery or intraarticular medications can each and all have important inflammatory effects, which lead to increased inflammatory markers. As a consequence, synovial fluid analysis in these cases quite commonly yields results that fall within what is considered the grey area as to the diagnosis of persistent synovial sepsis, and this makes interpretation and decision-making difficult. The absence of a gold standard for the diagnosis of synovial sepsis is limiting.

Clinical scenarios will be reviewed where the dilemma of what is happening, what the cause of persistent lameness is and a discussion on how to approach and manage these cases will be presented and discussed with the audience.

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