The Cytological Energy Detection of Purulent Inflammation in Synovial Fluid Is Not All Black and White

Neutrophils are frequently found in the cytological picture of synovial fluid in several joint pathologies, and a higher proportion of them can even wrongly indicate these cases as purulent inflammation. For reliable differentiation between purulent and non-purulent cases, we use the cytological energy analysis of the synovial fluid. Using this method, we examined 350 knee joint synovial fluid samples. Overall, we found that the percentage of neutrophils ranged between 20.0% and 50.0% in 44 (12.6%) cases and was above 50.0% in 231 (66.0%) cases. In the same group, only 85 (24.3%) highly anaerobic synovial fluid samples were evaluated as purulent inflammation, and another 17 (4.9%) cases were evaluated as very likely purulent inflammation. Further, we quantified the immediate risk of purulent inflammation using the "purulent score" (PS). Of the total of 350 samples, 103 (29.4%) cases were classified as having a very high risk of purulent inflammation (PS = 4), 53 (15.1%) cases were classified as having a significant risk of purulent inflammation (PS = 3), 17 (4.9%) cases were classified as having a moderate risk of purulent inflammation (PS = 2), and 75 (21.4%) cases were classified as having no immediate risk of purulent inflammation (PS = 1). Based on our results and analyses, the cytological energy analysis of synovial fluid is an effective method that can be used to detect and specify joint inflammation and the risk of septic arthritis development.