11. Knee Arthrocentesis

General Considerations

Indications:

  • Diagnostic: to determine etiology of an effusion.
  • Therapeutic: to drain large effusions or hemarthroses; to inject steroids or anesthetics.

Contraindications:

  • Absolute (pick another site):
    • Infection or psoriasis over entry site.
  • Relative (weigh risks and benefits in each patient individually):
    • Suspected bacteremia, although should perform if ruling out septic arthritis.
    • Prosthetic joint (should be performed by Orthopedics).

Technique

Preparation:

  • Obtain informed consent.
  • Review procedure with your supervisor and watch the NEJM “Arthrocentesis” video.
  • Gather supplies: marking pen or temp probe cover, chlorhexidine or betadine, 60mL syringe, 10mL syringe, 20g or 22g needle, 25g needle, 5mL 1% lidocaine, lavender and black top tubes, blood transfer device, 2 sets of sterile gloves, 2 face masks with eye shields, pillow/blanket to prop knee, chuck, wastebasket.
  • Palpate anatomic landmarks and the effusion. If unable to detect clinically significant effusion, consider orthopedic or rheumatology consultation for assistance.
  • Position patient supine on stretcher. Knee should be extended and then flexed at approximately 15-20˚. Place blanket or pillow underneath flexed knee to stabilize position.

Procedural steps:

  • Perform Time-Out. Complete and have an assistant co-sign the pre-procedure checklist.
  • Mark needle entry with marking pen or temp probe cover. Needle entry will be 1cm medial or lateral to the superior third of the patella and directed toward the intercondylar notch.
  • Ask about allergy to iodine. Prep the area with chlorhexidine or betadine.
  • Draw 5mL 1% lidocaine in 10mL syringe. Use 25g needle for your initial skin wheal and continue to anesthetize deeper tissues in anticipated trajectory of arthrocentesis. Remember to always aspirate while advancing your needle.
  • Use 20g needle attached to 60mL syringe for arthrocentesis. Direct the needle behind the patella and toward the intercondylar notch. Constantly pull back on the syringe while advancing until you enter the synovial cavity.
  • Remove as much fluid as possible. Consider ‘milking’ the effusion by gently compressing the suprapatellar region with the opposite hand. When aspiration is complete, remove needle, clean the site and apply a sterile bandage.

Complications

  • Iatrogenic infection, pain (think irritation from needle or joint-injection flare), joint instability, re-accumulation of fluid.

Diagnostic Studies

  • Send fluid for cell count/differential and crystal analysis (lavender top) and gram stain/culture (black top).
  • If septic arthritis is on the differential diagnosis, consult orthopedic surgery.

Knee Arthrocentesis

*May be negative if patient on antibiotics.

 

Ahmed I, Gertner E. Safety of arthrocentesis and joint injection in patients receiving anticoagulation at therapeutic levels. Am J Med. 2012 Mar;125(3):265-9. doi: 10.1016/j.amjmed.2011.08.022. PMID: 22340924.

Bettencourt RB, Linder MM. Arthrocentesis and therapeutic joint injection: an overview for the primary care physician. Prim Care 2010;37(4):691-702.

Thomsen TW, Shen S, Shaffer RW, Setnik GS. Videos in clinical medicine. Arthrocentesis of the knee. N Engl J Med 2006;354(19):e19.