What are the radiographic findings on an x-ray of an adult patient with a gout flare in the ankle?

Radiographic Findings of Acute Gout Flare in the Ankle

An x-ray of an acute gout flare in the ankle is typically normal or shows only non-specific soft tissue swelling, making plain radiography not useful for confirming the diagnosis of early or acute gout. 1

What You Will See in Acute Gout

Early/Acute Phase Findings

• Soft tissue swelling is the most common finding, but this is non-specific and can occur with any inflammatory process 1
• Normal joint spaces and bone architecture are typical in acute flares 1
• No erosions or tophi are visible in early disease 1

The EULAR guidelines explicitly state that radiographs are not useful in confirming the diagnosis of early or acute gout, with a strength of recommendation of 86% 1

Chronic Gout Findings (Not Applicable to Acute Flares)

If the patient has had untreated gout for years, you might see:

• Asymmetrical joint swelling (likelihood ratio 4.13 for differentiating chronic gout from other conditions) 1
• Subcortical cysts without erosion (likelihood ratio 6.39) 1
• "Punched-out" erosions with overhanging edges in advanced disease 1
• Tophi appearing as soft tissue masses, sometimes with calcification 1, 2

However, these features occur late in disease evolution and are not present during acute flares 1

Clinical Algorithm for Imaging in Suspected Ankle Gout

When Plain Radiography Is Appropriate

• Use x-rays primarily for differential diagnosis to exclude fracture, infection, or other bone pathology 1
• In long-standing disease (>2 years), x-rays can assess structural damage and chronic changes 1

Superior Imaging Modalities for Acute Gout

• Ultrasound is the preferred first-line imaging with 74% sensitivity and 88% specificity for the "double contour sign" indicating monosodium urate crystal deposition 1, 3, 4
• Dual-energy CT (DECT) shows 85-100% sensitivity and 83-92% specificity for detecting MSU crystals 1, 3, 5
• Both ultrasound and DECT can visualize crystal deposition even when x-rays are completely normal 1, 3

Critical Pitfalls to Avoid

• Do not rely on normal x-rays to exclude gout during an acute flare—radiographs are frequently normal apart from soft tissue swelling 1
• X-rays provide no information about crystal deposition or active inflammation in acute disease 1
• The absence of radiographic changes does not rule out gout, as characteristic features only appear after years of recurrent attacks 1
• If septic arthritis cannot be excluded clinically, joint aspiration with Gram stain and culture is mandatory regardless of imaging findings 3, 6

Definitive Diagnosis

The gold standard remains synovial fluid aspiration showing needle-shaped, negatively birefringent monosodium urate crystals under polarized light microscopy, with sensitivity and specificity approaching 100% 3, 6. Plain radiography plays only a minor role in diagnosis, though it may be useful for differential diagnosis and ruling out other conditions 1.