<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 38-year-old man comes to the physician because of progressive pain and swelling of his left knee for the past 2 days. He has been taking ibuprofen for the past 2 days without improvement. Four days ago, he scraped his left knee while playing baseball. He has a 2-month history of progressive pain and stiffness in his back. The pain starts after waking up and lasts for 20 minutes. He has type 2 diabetes mellitus. His older sister has rheumatoid arthritis. He is 170 cm 5 ft 7 in tall and weighs 91 kg 201 lb; BMI is 31.5 kgm2. Temperature is 39C 102.2F, pulse is 90min, and blood pressure is 13585 mm Hg. Examination shows an erythematous, tender, and swollen left knee; range of motion is limited. There are abrasions over the lateral aspect of the left knee. The remainder of the examination shows no abnormalities. Laboratory studies show a leukocyte count of 13,500mm3 and an erythrocyte sedimentation rate of 70 mmh. Which of the following is the most appropriate next step in management?? A: Bone scan, B: MRI of the left knee, C: Blood cultures, D: Arthrocentesis of the left knee, E: Continued ibuprofen intake,  <response>: This is a clinical vignette describing a 38-year-old man with progressive left knee pain and swelling for 2 days. He injured his knee 4 days ago playing baseball. He also has a 2-month history of back pain in the mornings. He has type 2 diabetes and a family history of rheumatoid arthritis. On exam, he has an erythematous, tender, swollen left knee with limited range of motion and abrasions. He has fever, leukocytosis, and an elevated ESR. This presentation is most consistent with septic arthritis given the acute onset of symptoms in the setting of recent trauma, fever, elevated inflammatory markers, and exam findings. The next step would be to aspirate the joint to analyze the synovial fluid and confirm the diagnosis.MRI could show effusion but would not provide information about the causative organism. Blood cultures could be positive but arthrocentesis is more likely to grow the organism. Bone scan and continued NSAIDs are not indicated at this point.D: Arthrocentesis of the left knee 