ABSTRACT
A 3 year old is brought to accident and emergency by his parents because he has not been walking for the past day and refuses to stand. He is normally fit and healthy but he did have antibiotics for tonsillitis 2 weeks ago. They do not think he has had any injuries but he attends daycare and something could have happened there. He is up to date with his immunizations and his parents have no concerns with his development. On examination he looks well, is apyrexial, with a heart rate of 120 and respiratory rate of 26 with no bruising. His knees are normal on examination and the hips have a full range of movement except he cries on external rotation of the right hip. There are no deformities seen on x-ray of the hips and knees. After some paracetamol he manages to stand and take a few antalgic steps with encouragement, limping on the right leg. What is the most likely diagnosis?
