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What is the diagnosis?

The most likely diagnosis is septic arthritis of the right wrist.  The differential includes gout, pseudogout, Lyme disease, osteoarthritis, or systemic disease.  The overall incidence of septic arthritis in a erythematous swollen wrist is 3-5% [1].

• Pearl: Patients diagnosed with septic arthritis of the wrist often have medication-induced immunosuppression, diabetes, cirrhosis, kidney failure, or a history of wrist trauma [1].

What is the mechanism of injury?

Septic arthritis of the wrist is often not accompanied by an acute injury, although recent instrumentation is a risk factor for infection. This patient did have a recent steroid injection in the wrist. They also have a history of diabetes, and are immunosuppressed, likely leading to infection.

What physical exam findings are expected?

Septic arthritis often presents with warmth, erythema, swelling, pain with motion, and fever.  There is no physical exam finding that definitively diagnoses or rules out septic arthritis, although several findings are suggestive of it. 

• Pearl:  There are no published laboratory or clinical criteria that reliably differentiate septic arthritis from inflammatory arthropathy [1].

Which imaging modalities can be used?

X-ray, ultrasound, and MRI can all aid in the diagnosis of septic arthritis of the wrist, but none of them provide a definitive diagnosis.  Radiographs typically demonstrate soft tissue swelling or a joint effusion [2].

What is the management in the ED?

The next step is joint aspiration [3]. Clinicians should also obtain X-rays, labs (including ESR, CRP, and Blood Cultures), and admit the patient. There are multiple approaches to wrist arthrocentesis.  The most common is a dorsal approach. Identify Lister's tubercle. Anesthetize the area. Prep the skin. Use a 20-21 gauge needle for aspiration. Insert needle perpendicular to the skin on the ulnar side of the extensor policis longus tendon, radial to the extensor carpi radialis brevis tendon. If you hit bone, withdraw and redirect [4]. Ultrasound (image 2) may be used to help guide aspiration. If there is high enough suspicion for septic arthritis of the wrist the patient will need to be admitted to the hospital on antibiotics.

Image 2: Courtesy of David Carrol, Radiopedia.org rID:92758. Ultrasound of wrist. LT: Lister's tubercle. ECRB: Extensor carpi radialis brevis. ECRL: Extensor carpi radialis longus

When do you consult Orthopedics?

If there is high enough suspicion for septic arthritis, orthopedics should be consulted urgently from the emergency department.