History An 84-year-old woman with diabetes has been admitted to the emergency department with an acutely swollen and painful left knee. She has been unwell with a raised temperature and productive cough for the last week and for the last 24 hours has been unable to bear weight because of her knee pain. Examination This elderly woman is unwell, sweaty and febrile. Her pulse is 108 bpm and blood pressure 98/60 mmHg. Oxygen saturation on room air is 92 per cent. Her left knee is held rigid in fixed flexion and is hot and red with a moderate effusion.
Her respiratory rate is 22/min. There is decreased expansion on the right side, with dullness to percussion, increased vocal resonance and coarse crackles at the base. The remainder of her examination is normal. What is the diagnosis and likely explanation for the right knee pain and swelling? Is the diagnosis and likely explanation for the…
