Which ED procedure involves removing fluid from a joint for diagnostic analysis?

• A. Lumbar Puncture
• B. Paracentesis
• C. Thoracentesis
• D. Arthrocentesis

Answer: (D)

Arthrocentesis is the procedure of removing fluid from a joint for diagnostic analysis. In the ED, a clinician uses aseptic technique to aspirate synovial fluid from a joint (often the knee) so it can be analyzed in the lab. The fluid is examined for cell count, Gram stain, culture, and crystals to distinguish septic arthritis from inflammatory or crystal-induced arthritis and to guide treatment. Other procedures collect fluids from different body spaces: a lumbar puncture retrieves cerebrospinal fluid around the spinal cord, paracentesis withdraws ascitic fluid from the abdominal cavity, and thoracentesis removes pleural fluid from the space around the lungs. Thus, fluid from a joint points to arthrocentesis.