(Click the link to comment and to vote – voting not working through email, sorry!)

A 20 month old boy is brought in by his mother for refusal to bear weight on the right leg. She was at work all day and the child went to the park with his father, but no known trauma occurred. He has had no fever, URI symptoms, or rash. He was born full-term and has no significant past medical history. Physical exam of his right leg is unremarkable. AP and lateral X-rays are as shown. 

What is the next best step in management?