Eric Curran, MS IV
Article: Tao Wu, et al. “Ultrasound-guided versus landmark in knee arthrocentesis: A systematic
review.” Seminars in Arthritis and Rheumatism 2016; 45:627-632.
Background: Intra-articular joint injections have typically been performed “blind”, or guided by
palpation using common anatomic landmarks (LM). The first overview of ultrasound-guided
(USG) applications in relation to the musculoskeletal system was published in 1988 and since
then, numerous studies have shown improved accuracy of joint injections with an image-guided
approach. However, no systematic reviews have directly compared USG and LM arthrocentesis.
This systematic review assesses the efficacy of USG versus LM knee arthrocentesis in adults
with knee pain or effusion.
Methods: This study included randomized or non-randomized controlled trials comparing the
accuracy or clinical efficacy between USG and LM arthrocentesis of the knee joint. The
outcomes of interest were accuracy rate, pain during treatment, aspirated fluid volume, pain
score after 2 weeks of injection, and procedure duration. For summarization of the accuracy rate
in arthrocentesis, a risk ratio (RR) was used. For continuous outcomes (eg, pain score during
treatment), a weighted mean difference (WMD) was used.
Results: Nine studies were eligible for this review, with a total of 715 adult patients (725 knee
joints). Outcomes, by category, comparing USG versus LM technique were as follows:
Knee arthrocentesis accuracy: RR = 1.21, P < 0.001.
Procedural pain score (visual analog score, 0-10): WMD = -2.24, P < 0.001.
Note: the minimal clinically important difference was calculated as > 1.4.
Aspiration volume: WMD = 17.06, P = 0.003.
Pain score 2 weeks after injection: WMD = 0.84, P < 0.001.
Procedure duration: no statistically significant difference (WMD = -0.8, P = 0.31).
Study Challenges: Participants were not blinded to the treatment in seven out of the nine trials
included in this review. This may have resulted in bias, especially for subjective measures such
as the visual analog score for pain. Moreover, there are generally six anatomic approaches to
arthrocentesis and only one study included in this review compared accuracies of these
approaches. If differences in technical difficulty or success-rate exist among these approaches,
such differences may have skewed comparisons drawn in this study. Of note, the study that did
compare approaches found the accuracy rate of the superior lateral approach to be the highest,
at 100%. In addition, the relatively small sample size, use of cadavers in one study, varying
interventions in selected studies (eg, aspiration or injection) and potential for varying provider
experience levels may have limited generalization of the study findings.
The Takeaway: The meta-analysis here offers evidence that in adults with knee pain or joint
effusion, USG knee joint arthrocentesis offers greater accuracy, efficacy, and clinical
improvement over LM technique. As a result, the use of USG techniques in joint arthrocentesis
can potentially improve patient outcomes and even lower healthcare costs. Moreover, when
considering applications to clinical practice, it is important to realize that additional benefits to
USG arthrocentesis exist, such as the analysis of the depth and viscosity of the effusion as well
as real-time procedural visualization. Additional areas of research can focus on comparing USG
success rates to provider experience level and analysis of additional anatomic sites and
applications beyond knee arthrocentesis.