In septic arthritis, which statement is true regarding diagnosis?

• A. It relies solely on imaging
• B. It requires documentation of pathogens by culture or NAAT
• C. It is never caused by bacteria
• D. It always presents with fever

Answer: (B)

Diagnosis depends on proving the infection by identifying the organism in the joint, usually through culture of synovial fluid or molecular testing such as NAAT. Imaging can show a joint effusion or inflammation but cannot confirm infection by itself, so it’s not sufficient alone. Culturing the synovial fluid is the standard way to document the pathogen, and NAAT can be especially helpful if cultures are negative or slow-growing. Bacteria can cause septic arthritis, so the statement that it’s never bacterial is incorrect, and fever isn’t always present.