Q. A 5-year-old boy has been brought to the emergency department by his mother with a swollen and painful right knee after a minor fall while playing. The child has a history of easy bruising and prolonged bleeding after dental procedures. The patient's family history is significant for a maternal uncle with a similar bleeding disorder. His temperature is 98.4°F (36.8°C), heart rate is 90/min, respiratory rate is 14/minute, and blood pressure is 110/70 mm of Hg. On physical examination, there is significant swelling and tenderness of the right knee joint. X-ray shows right knee joint effusion. Laboratory tests are shown below. What is the most appropriate next step in the management of this patient?