A 5-year-old boy is brought to the clinic for evaluation of a 5-week history of left thigh pain. His mother reports that he fell from a ladder while playing about 6 weeks ago. Three weeks ago, he had a self-limited upper respiratory infection with rhinorrhea. He has no history of serious illness, has met all developmental milestones, and is fully immunized. Family history is notable for asthma in his 7-year-old brother. Growth parameters are at the 60th percentile for height and 65th percentile for weight. He appears well and in no acute distress. Temperature is 37.1°C (98.8°F), pulse is 88/min, respirations are 17/min, and blood pressure is 110/70 mm Hg. Gait examination shows a mild left-sided antalgic gait. The left groin is tender to palpation, and hip abduction and internal rotation are limited by pain. The remainder of the physical examination is unremarkable. Laboratory studies, including hemoglobin, leukocyte count, and platelet count, are within normal limits. Pelvic radiograph demonstrates a left femoral epiphysis that is smaller than the right with widening of the medial joint space on the left; the femoral head shows minimal structural damage. Which of the following is the most appropriate next step in management?