Comparison of Ultrasound-Guided and Standard Landmark Techniques for Knee Arthrocentesis

Background: Ultrasound is a useful adjunct to many Emergency Department (ED) procedures. Arthrocentesis is typically performed using a landmark technique but ultrasound may provide an opportunity to improve arthrocentesis performance. Objective: To assess the success of emergency physicians performing landmark (LM) vs. ultrasound (US)-guided knee arthrocentesis techniques. Methods: This was a prospective, randomized, controlled study of patients requiring knee arthrocentesis who presented to one urban university ED and two community EDs between June 2005 and February 2007. Results: There were 66 patients enrolled (39 US-guided, 27 LM). Among all users, there was no difference in arthrocentesis success (US 37/39 vs. LM 25/27); p = 1.0. Secondary Endpoints: 1) Patients reported less pain with ultrasound; US-guided 3.71 (95% confidence interval [CI] 2.61–4.80) cm vs. LM 5.19 (95% CI 3.94–6.45) cm; p = 0.02. 2) Providers felt the US-guided technique was easier to perform than LM; 1.67 units on 5-point scale (95% CI 1.37–1.97) vs. 2.11 (95% CI 1.79–2.42) units; p = 0.02. 3) The total procedure time was shorter with the US-guided technique; 10.58 (95% CI 7.36–13.80) min vs. LM 13.37 (95% CI 9.83–16.92) min; p = 0.05. 4) There was no difference in the amount of fluid obtained between techniques; US-guided 45.33 (95% CI 35.45–55.21) mL vs. LM 34.7 (95% CI 26.09–43.32) mL; p = 0.17. Conclusion: US-guided knee arthrocentesis technique does not improve overall success of obtaining joint fluid aspirate vs. the standard LM and palpation technique. An US-guided approach does not result in more pain for the patient, takes no additional time to perform and, at least for novice physicians, leads to more fluid aspiration and greater novice provider confidence with the procedure. Further studies with more participants and standardization of anesthetic quantity are required to validate these findings.