We will recruit 20 subjects from our healed Perthes' population. We will use dGEMRIC imaging to identify regions of cartilage degeneration in the femur and acetabulum. Both hips will be imaged so that we can use the unaffected side as a control. We will apply dGEMRIC imaging, which allows the composition of cartilage (specifically, the concentration of glycosaminoglycans [GAGs], important structural proteins in the cartilage) to be assessed.