The Effect of Perthes' Disease on Hip Cartilage

Inclusion Criteria: * Subjects must have reached the healed stage of unilateral Perthes' disease. -Subjects will be between 7 and 18 years of age. * Subjects must understand English. Exclusion Criteria: * Subjects will be excluded if they have bilateral Perthes' disease or if they have not yet reached the healing stage of the disease. * Subjects will also be excluded if they do not meet the criteria to have an MRI (e.g., the subject has metal implants, is claustrophobic, has a metallic object in eye or a pacemaker). * A subject will be excluded if they have any of the precautions for the MR contrast agent, Magnevist, such as pregnancy, breast-feeding, respiratory allergies, asthma, thrombotic syndromes, history of grand mal seizures, impaired renal or hepatic function.