Synovial Fluid Biomarker Alternatives Can Plasma and Urine Samples Shed Light on the Post-Traumatic Intra-Articular Microenvironment?

The purpose of this study was to analyze the relationship between the intra-articular inflammatory response and any associated systemic inflammatory response following knee injury requiring operative management. Patients undergoing primary knee arthroscopy provided synovial fluid, blood, and urine samples immediately prior to surgery. Samples were analyzed using a multiplex magnetic bead immunoassay for the concentrations of cytokines and growth factors that have been shown to be associated with post-injury inflammation. One hundred and fifty-one patients undergoing arthroscopic management of meniscus, ACL, and focal chondral lesions were included in the analysis. After correction for multiple tests, there were no statistically significant correlations between synovial fluid biomarkers and biomarkers in plasma or urine for any of the intra-articular pathologies assessed. This analysis suggests that the most accurate measurement of the post-injury inflammatory response must be sampled from the intra-articular space. In the post-traumatic knee, there is no substitute for synovial fluid biomarker analysis.