Which option lists the three Cs used in diagnosing septic arthritis?

• A. Inflammatory markers, imaging, and culture
• B. Crystal analysis and imaging
• C. Cell count/diff, Crystals, and Culture
• D. Culture and sensitivity only

Answer: (C)

Diagnosing septic arthritis hinges on a direct analysis of the affected joint’s synovial fluid. The three Cs are Cell count with differential, Crystals, and Culture. The cellular analysis looks for an infectious/inflammatory pattern in the fluid, with a high white blood cell count and neutrophil predominance typical of septic arthritis. The crystal analysis helps distinguish crystal-induced arthritis, such as gout or pseudogout, from infection; crystals can be present or not, but their findings help avoid misdiagnosis and ensure appropriate treatment. The culture aims to identify the causative organism and guide targeted antibiotics; a positive culture confirms infection and directs therapy, while a negative culture doesn’t completely rule out infection but makes management more challenging.

Other tests like inflammatory markers and imaging can support suspicion but are not specific for septic arthritis and may be present in many other conditions, so they don’t alone establish the diagnosis. Culture alone misses information about the inflammatory cell response and crystal status, so it doesn’t provide a complete picture. That combination of cellular analysis, crystal assessment, and culture best represents what’s used to diagnose septic arthritis.