From the Guidelines
Diagnosing gout in the knee is most definitively done through joint fluid analysis, where a healthcare provider examines the fluid for urate crystals under a microscope, as recommended by the European League Against Rheumatism in 2020 1.
Key Diagnostic Steps
- Joint fluid analysis for urate crystals is the gold standard for diagnosis, with a level of evidence of 2b and a grade of recommendation of B, as per the European League Against Rheumatism guidelines 1.
- Clinical evaluation, including sudden, severe knee pain, redness, warmth, swelling, and extreme tenderness to touch, can support the diagnosis.
- Laboratory tests, such as blood tests measuring uric acid levels, can be helpful but are not definitive.
- Imaging tests like X-rays, ultrasound, or dual-energy CT scans can detect crystal deposits and joint damage in chronic gout.
Importance of Early Diagnosis
- Patients should seek medical attention during an acute attack rather than after symptoms subside, as this allows for proper joint fluid analysis.
- The American College of Rheumatology diagnostic criteria consider clinical presentation, laboratory findings, and response to treatment when making a diagnosis.
- A history of gout in other locations, such as the big toe, can strengthen the diagnosis when knee symptoms develop.
Diagnostic Considerations
- The diagnosis of gout should not be made on the presence of hyperuricaemia alone, as stated in the European League Against Rheumatism guidelines 1.
- Risk factors for chronic hyperuricaemia, such as chronic kidney disease, overweight, and excess alcohol consumption, should be considered in the diagnostic process.
- Systematic assessment for associated comorbidities, including obesity, renal impairment, hypertension, and diabetes, is recommended in patients with gout, as per the European League Against Rheumatism guidelines 1.
From the Research
Diagnosis of Gout of the Knee
To diagnose gout of the knee, several methods can be employed, including:
- Clinical prediction rules, which have been validated for diagnosing gout 2
- Arthrocentesis, which should be performed when there is suspicion of an underlying septic joint 2
- Synovial fluid or tophus analysis, which can be performed if the diagnosis is uncertain 2, 3
- Demonstrating the presence of monosodium urate (MSU) crystals in the joint fluid or tophus, which is considered the gold standard for diagnosis 3
- Clinical, radiologic, and laboratory criteria, which can be helpful in the absence of demonstrating MSU crystals 3
Clinical Presentation
Gout is characterized by:
- Swelling, pain, or tenderness in a peripheral joint or bursa, including the development of a tophus 2
- Acute gouty arthritis, which typically presents with a sudden and severe exquisitely painful joint 3
- Risk factors, including male sex, obesity, hypertension, alcohol intake, and others 2
Laboratory and Radiologic Findings
Laboratory and radiologic studies can be helpful in making the diagnosis of gout, including: