You are answering a USMLE-style medical question. Question: A 13-year-old boy is brought to the emergency department because of pain in his right knee for the past week. The pain is exacerbated by jogging and climbing up stairs. He has no history of trauma to the knee. He is otherwise healthy. He is an active member of his school's gymnastics team. His vital signs are within normal limits. Examination of the right knee shows a tender swelling at the proximal tibia; range of motion is full. Knee extension against resistance causes pain in the anterior proximal tibia. The remainder of the examinations shows no abnormalities. X-ray of the right knee shows anterior tibial soft tissue swelling with fragmentation of the tibial tuberosity. Which of the following is the most appropriate next step? Options: A) Administration of oral ketorolac B) Perform joint aspiration C) Open reduction of the tuberosity D) Application of a lower leg cast " Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.