Painful hip and limping

A 6-year-old young boy is brought in for evaluation of a painful hip. He has been limping and not wanting to walk for the past 2 days. He has had no obvious injury. He feels a little better if he is given some ibuprofen. He has not had a fever and does not have any other current symptoms, although he had "the flu" last week. On examination, his vital signs are normal. His right hip has some pain with internal rotation. He walks with a pronounced limp.