🦴 Joint Pain · Septic vs Reactive · JIA · Lyme · Rheumatic Fever · Trauma

Schwartz Clinical Handbook — Chapter 47 · Septic arthritis · Transient synovitis · Osteomyelitis · JIA · Acute rheumatic fever · Leukemia · Lyme

Select joint count (mono vs poly), fever, warmth/swelling, refusal to bear weight, rash, preceding URI, tick bite, and lab clues (CRP/ESR, synovial fluid) → differentiate septic arthritis (urgent), transient synovitis, JIA, acute rheumatic fever, Lyme arthritis, reactive arthritis, or malignancy.
⚠️ Red flags: fever, inability to bear weight, erythema over joint, severe pain with passive motion → septic arthritis, joint aspiration and IV antibiotics.

📋 Step 1 — Joint count & inflammatory signs
📌 Diagnostic impressions
📖 Schwartz Ch 47

Select number of joints (monoarticular, pauciarticular, polyarticular), fever, warmth, swelling, refusal to bear weight, rash, preceding illness (URI, pharyngitis, tick bite), and lab clues (CRP/ESR, synovial fluid WBC) → differentiate septic arthritis, transient synovitis, JIA, rheumatic fever, Lyme arthritis, reactive arthritis, or leukemia.

✔️ Septic arthritis: hot, swollen, limited ROM, fever, high CRP, synovial WBC >75k.
✔️ Transient synovitis: afebrile, mild symptoms, resolves with rest.
✔️ JIA: morning stiffness, ≥6 weeks duration, pauci/polyarticular.
✔️ ARF: migratory polyarthritis, carditis, chorea, elevated ASO.
✔️ Lyme: monoarthritis (knee), erythema migrans, endemic area.
📘 Schwartz pearls (Chapter 47)
• Septic arthritis: joint aspirate for culture — emergency washout.
• Kocher criteria (≥3 of: fever, non‑weight‑bearing, ESR ≥40, WBC >12k) → high risk septic hip.
• Lyme arthritis: serology (ELISA + Western blot), treatment with doxycycline (or amoxicillin if <8y).
• JIA: rule out malignancy (CBC, smear, LDH, uric acid).
• Transient synovitis: observation if afebrile, normal CRP, improvement within 72h.