Differential diagnosis of joint pain

1. Big picture

Joint pain is not a diagnosis. The examiner wants you to decide first whether the pain is:

1. Articular or periarticular
2. Inflammatory or mechanical
3. Monoarticular, oligoarticular, or polyarticular
4. Acute dangerous arthritis or chronic rheumatic disease

The most important emergency rule:

Acute hot swollen joint = septic arthritis until proven otherwise
→ aspirate the joint urgently before antibiotics if possible
→ then start empiric antibiotics

The biggest exam trap is to treat every painful joint with non-steroidal anti-inflammatory drugs (NSAIDs) without excluding septic arthritis, crystal arthritis, trauma, hemarthrosis, or systemic inflammatory disease.

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