OR3.2 | Joint Aspiration Practice — Summary & Reflection

KEY TAKEAWAYS

Joint aspiration is a diagnostic and therapeutic procedure requiring knowledge of anatomy, strict aseptic technique, and systematic fluid interpretation. The key surface landmarks for each joint — knee (superolateral patella), shoulder (posterior acromion), ankle (anteromedial joint line), hip (ultrasound-guided) — must be memorised. Aseptic technique is non-negotiable: skin prep must fully dry, sterile drapes must cover the field, and needle-to-tissue contact must never contaminate the sterile zone. The critical diagnostic threshold for septic arthritis is synovial WBC >50,000/μL with >90% neutrophils. A negative Gram stain does not exclude infection — culture is the gold standard, and it must be sent before antibiotics. The Kocher criteria (non-weight-bearing, ESR >40, fever >38.5°C, WBC >12,000) risk-stratify paediatric hip cases: ≥2 criteria (~40% probability) warrants urgent aspiration and probable surgical washout. Specimen tube selection is critical: EDTA for cell count, sterile plain bottle for culture, fluoride tube for glucose.

REFLECT

You are assisting in the emergency department when a 7-year-old is brought in with a 36-hour history of right knee pain, fever of 38.8°C, and refusal to walk. His WBC is 14,500, CRP 88 mg/L, ESR 48 mm/h. Knee X-ray shows only soft-tissue swelling. Your registrar says: 'We should start antibiotics now and aspirate in the morning when the orthopaedic team arrives.' What is your response? Reflect on the sequence of diagnostic steps, the urgency of the situation, and how you would communicate your concern to the registrar respectfully but clearly.