A teenager with knee pain

Case presentation

History and examination

A 15-year-old boy wearing a knee guard presented with a five-month history of left knee pain and an associated limp. Several months previously, he had presented with the same features to the emergency department of a major teaching hospital. An x-ray and MRI of the knee had been performed, which were normal in appearance (Figure 1). He was subsequently referred to a rheumatologist, who arranged x-rays of the hip (Figure 2) and bone scans (Figure 3). On the basis of these findings, the patient was urgently referred to an orthopaedic surgeon.