arthrocentesis2A patient comes into the ED and you suspect septic arthritis to the knee. As you consent the patient for arthrocentesis, you can tell s/he has reservations about a needle being inserted into their knee and left in place while you aspirate. You also think in the back of your mind how tricky it is to sometimes change syringes while keeping the needle in the correct location. Is there another way of tapping the knee without a needle?


Trick of the Trade: Use the angiocatheter for knee arthrocentesis

  • Prepare for arthrocentesis in the usual fashion (anteromedial or anterolateral approach)
  • Instead of attaching a needle to the syringe, attach an 18 gauge angiocatheter
  • Insert the angiocatheter while aspirating back on the syringe
  • When synovial fluid is aspirated, advance the catheter into the joint and remove the angiocatheter needle
  • The plastic catheter is left in the joint for aspiration


  • No metal needle left in the knee, which may comfort some patients
  • No needle to secure if you need to change syringes
  • Convenient way to also administer intraarticular steroids/analgesics
  • Joint/catheter can be manipulated without fear of causing tissue injury


  • Milk the joint/effusion to facilitate fluid collecting in the joint space
  • Slight manipulation of the joint may help the fluid re-distribute into the joint space
  • Aspirate as you slowly withdraw the catheter in case there is a residual fluid pocket
  • Be aware of a kinked catheter as an extreme angle may impede aspiration

Other pearls regarding septic arthritis? Check out synovial lactate for septic arthritis and the Paucis Verbis card: Septic Arthritis.

Has anyone tried the angiocatheter technique for knee arthrocentesis? We’d love to hear about your experience!

Fred Wu, MHS, PA-C

Fred Wu, MHS, PA-C

Lead PA
Department of Emergency Medicine
Kaweah Delta Medical Center (Visalia, CA)
Fred Wu, MHS, PA-C

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