Transient synovitis of the hip

Case history

A 3-year-old boy is seen in the emergency department at 2 a.m. because he is crying. He is otherwise healthy. Earlier in the day he was playing, but his mother noted that he may have had a limp. He has no fever and otherwise feels well. On physical exam, slight movement of his hip is tolerated but excess motion causes him to cry. His complete blood count and erythrocyte sedimentation rate are normal.