When aspirating a joint, which set comprises the three core components?

• A. Crystal analysis, Culture & sensitivity, Imaging
• B. Cell count with differential, Imaging, Crystal analysis
• C. Cell count with differential, Culture & sensitivity, Crystal analysis
• D. Culture & sensitivity, Crystal analysis, Imaging

Answer: (C)

The key set of analyses for an aspirated joint is to evaluate the synovial fluid for cell content, crystals, and infectious organisms. This trio directly helps distinguish septic arthritis from crystal-induced and noninfectious inflammatory processes. The cell count with differential tells you how many cells are present and the proportion of neutrophils, with higher neutrophil-dominant counts suggesting infection or inflammatory arthritis. Crystal analysis looks for monosodium urate crystals (gout) or calcium pyrophosphate crystals (pseudogout), identifying crystal-induced arthritis. Culture and sensitivity checks for bacteria and guides antibiotic therapy if infection is present, confirming septic arthritis and informing treatment choices. Imaging, while valuable for guiding needle placement and assessing joint structure, is not part of the fluid analysis itself. Together, these three fluid analyses provide a comprehensive, rapid assessment to direct appropriate management.