Introduction

Emergency physicians must consider septic arthritis when evaluating patients presenting with a painful and swollen elbow. The clinical exam, even in combination with serum laboratory markers, is not adequately sensitive to rule out a septic joint making arthrocentesis with synovial fluid analysis mandatory once the presence of a new effusion has been verified.¹

Overlying tissue edema and obesity often limit the ability of clinicians to assess accurately the presence of an effusion and palpate classic landmarks needed for “blind” joint aspiration.²

Sonography has proven to be superior to both the physical exam and plain film radiography in detecting the presence of joint effusions, while also confirming alternative diagnoses such as cellulitis, abscesses, and soft tissue hematomas.^3,4

The absence of effusion in the capsule surrounding the elbow joint on ultrasound (in conjunction with the clinical exam) may prevent an unnecessary invasive joint aspiration.⁴

Along with delineating anatomical landmarks and detecting the presence of joint effusion, point-of-care ultrasound can be used to guide needle aspiration during arthrocentesis.

Ultrasound guidance has been shown to improve success rates compared to classic landmark techniques, and having a simple protocol can be invaluable for the clinician performing elbow arthrocentesis.⁵

Procedure

Elbow Effusion Identification by Bedside Ultrasound

We recommend using the linear transducer (10-5MHz) for both the identification of the effusion and needle guidance for the arthrocentesis (Pic 1A). The elbow can be assessed for the presence of effusion from both the lateral and posterior approaches, with the lateral approach preferred for arthrocentesis.

We always recommend first examining the non-affected elbow with ultrasound for clinical comparison of the joint capsule. For the lateral approach to the elbow joint capsule, the goal is to find the soft triangular junction between the lateral epicondyle of the humerus, the radial head, and the olecranon.

The patient should be placed in a sitting upright position with the affected arm abducted, resting to the patient’s side, pronated, and flexed to 90 degrees (Pic 2). Place the transducer along the proximal forearm in a longitudinal fashion, parallel to the shaft of the radius, and with the probe marker towards the patient’s head.