History An 84-year-old diabetic woman has been admitted to the emergency department with an acutely swollen and painful left knee. She has been sick with a high temperature and productive cough for the last week. In the last 24 hours, she has been unable to tolerate the weight because of her knee pain. Examinations This elderly woman is unwell, febrile, and sweaty. Her blood pressure is 98/60 mmHg, respiratory rate 22/min, and pulse 108 bpm.
Her left knee is held rigid in fixed flexion and is hot and red with a moderate effusion. There is a decreased expansion on the right side, with dullness to percussion, coarse crackles at the base and increased vocal resonance. The remaining examination is normal. Haemoglobin 14.2 g/dL (13.3–17.7 g/dL) White cell count 18.3 x 109/L (3.9–10.6 x 10 9 /L) Platelets 542 x 10 9 /L (150–440 x 10 9 /L) ESR 45…
