AS equine practitioners, we all know that diagnosing synovial sepsis can sometimes be challenging when trying to distinguish between early stage infective arthritis, with a relatively low total nucleated cell count (TNCC), and traumatic arthritis with a high white blood cell count. 1 Another challenge can be obtaining enough synovial fluid, if any, to allow determination of the three most useful parameters in making the diagnosis of septic synovitis: TNCC, neutrophil percentage and total protein. Under the worst circumstances, if a very chronic septic process is encountered with extensive soft tissue trauma or infection and large wounds, synovial cavity puncture, aspiration and withdrawal may not be possible or should even be discouraged (Fig 1). In these particular circumstances, a systemic quick, affordable sensitive and specific synovial biomarker test to aid the immediate diagnosis is needed to allow clinical therapeutic decisions to be made rapidly. In a study by Robinson and others, 2