Question category: Rheumatology
A 60 year present with a swollen left painful knee. She is known to have rheumatoid arthritis, being treated with methotrexate and hydroxychloroquine. She feels unwell and is pyrexial. On examination the knee is very warm, swollen and movement of knee is very restricted. Her bloods show raised inflammatory markers and a normochromic, normocytic anaemia and elevated white cell count. What is the most important management?