Arthrocentesis is defined as which procedure?

• A. Aspiration/injection of joints
• B. Biopsy of synovial tissue
• C. Injection into bone marrow
• D. Arthroscopic visualization

Answer: (A)

Arthrocentesis is the puncture of a joint with a needle to reach the joint space in order to withdraw synovial fluid (aspiration) and, if needed, to inject medications into the joint. This procedure is used both for diagnostic purposes—analyzing the fluid for infection, crystals, or inflammatory cells—and for therapeutic relief of effusion or pain with injections like corticosteroids. It is distinct from arthroscopy, which uses a camera to directly visualize the inside of the joint; from bone marrow procedures, which target the bone marrow itself; and from synovial biopsy, which collects tissue from the synovial lining rather than fluid.