Review Question - QID 214313

A 3-year-old well appearing child has refused to walk for the past 2 days. His parents report no known injuries. Examination in the emergency department reveals a temperature of 102.2 degrees F (39 degrees C) and limited range of motion of the left hip. An AP pelvic radiograph is normal. Laboratory studies show a WBC count of 9,000/mm3, an erythrocyte sedimentation rate (ESR) of 50 mm/h, and a C-reactive protein level of 5 mg/dL (normal <1mg/dL). What is the next most appropriate step in management?