CRP and infection: There are three possibilities: infection unlikely, infection likely, and infection established based on the following data: clinical and blood workup (clinical features, CRP); synovial fluid cytological analysis (leukocyte count (cells/μL); polymorphonuclear percentage); synovial fluid biomarkers (alpha-defensin); microbiology (aspiration fluid, intraoperative fluid and tissue, sonication (CFU/mL); and histology (high-power field, 400× magnification).