A 13 year old boy presented to the accident and emergency department because he was unable to bear weight on his left leg and had a history of pain in the left knee. The pain began 10 days before, after a fall, at which time he had a dull pain in his knee but was still able to bear weight. Three days before his attendance he tripped again, and after this injury, the pain had become more severe and he was unable to bear weight. He was otherwise healthy, with no history of joint problems. He was not particularly active or sporty and had a body mass index of 25.6. On examination, he was in moderate pain and was unable to bear weight. Both knees were normal, but his left leg was shortened and externally rotated, with no evidence of bruising or injury. Examination of his left hip showed limitation of flexion, abduction, and, in particular, internal rotation because of pain. All other joint examinations were unremarkable. He underwent radiography (fig 1⇓). ### 1 What type of radiograph is this and what does it show? #### Short answer Figure 1 is a “frog lateral” radiograph and it shows a widened physis and malalignment of the epiphysis and proximal femoral metaphysis (fig 2⇓), confirming the diagnosis of a left slipped upper femoral epiphysis. Fig 2 Frog lateral radiograph showing a widened physis and malalignment of the epiphysis and proximal femoral metaphysis on the left side #### Long answer Slipped upper femoral epiphysis is the transphyseal displacement of the upper femoral epiphysis from the metaphysis.1 Frog lateral (while the patient is supine with both knees flexed, soles …