How to perform arthrocentesis on a joint

In this Medmastery article, learn about the basic arthrocentesis procedure, and the tools you'll need to tap a joint.
Last update19th Nov 2020

Identifying the tools for an arthrocentesis

Performing an arthrocentesis is also called tapping a joint. To tap a joint, you will need several tools:

  • A 25 gauge (G) needle and a 3 cc syringe for anesthesia
  • Lidocaine or ethyl chloride freeze spray for anesthesia
  • Sterilizing solution (e.g., chlorhexidine)
  • Sterile gloves
  • Sterile drape
  • Fluid collection container (e.g., urine collection cup)
Figure 1. To perform an arthrocentesis, you will need several tools such as a 25 gauge (G) needle, a 3 cc syringe, anesthesia solution such as lidocaine or ethyl chloride, sterilizing solution, sterile gloves, sterile drape, and a fluid collection container.

So, now that you know what you need to perform an arthrocentesis, what do you do with these tools?

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How to perform arthrocentesis on a joint

The arthrocentesis procedure requires seven simple steps to ensure a safe, clean, and painless tap:

  1. Mark your site by pushing a needle cap on the skin to create a landmark for the needle.
  2. Put on sterile gloves and lay down a sterile drape.
  3. Clean the skin with sterilizing solution, such as a chlorhexidine swab.
  4. Anesthetize the area with 0.5 cc of lidocaine or ethyl chloride spray.
  5. Tap the joint using a needle and syringe, sized appropriately for the joint you’re tapping.
  6. Remove the joint fluid and place in a container.
  7. Send the fluid to a lab for cell count, culture, gram stain, and crystal evaluation.
Figure 2. How to perform arthrocentesis on a joint. 1) Create a landmark by pushing a needle cap into your patient's skin to mark the site. 2) Use sterile gloves and drapes. 3) Sanitize the area. 4) Anesthetize the area. 5) Tap the joint. 6) Remove the joint fluid and place in a collection container. 7) Send the fluid to a lab for cell count, culture, gram strain and crystal evaluation.

Congratulations, now you know the tools and basic procedures for performing an arthrocentesis!

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Recommended reading

  • Roberts, J. 2019. “Arthrocentesis”. In: Roberts and Hedges’ Clinical Procedures in Emergency Medicine and Acute Care. 7th edition. Philadelphia: Elsevier.  

About the author

Siamak Moayedi, MD
Professor and Director of Medical Student Education, University of Maryland and Course Director, Essential and Critical Procedures, Emergency Medicine.
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