Discriminating septic and non-septic arthritis when investigating an equine synovial fluid is the most frequent and relevant objective. Definitive diagnosis (bacteria isolation) is often established lately when effectively achieved. In adjunction to the microbiological investigation, the practitioner should then regularly rely on a combination of other criteria in order to determine the treatment to be performed. Among these criteria are notably the macroscopic aspect of the synovial fluid, total and differential cellular count, biochemical parameters (total proteins or de lactates), as well as serum and/or synovial dosage of different biomarkers such as serum amyloid A (SAA), myeloperoxidase (MPO) or elastase (ELT).