The 11 categories of musculoskeletal conditions that follow represent the most common health care reasons for which children and adolescents are seen in doctors' offices, emergency departments, and hospitals. A number of these conditions, such as the skeletal dysplasias, are relatively rare, diagnosed infrequently in the health care system, and have little data available on prevalence and burden. Yet, though rare, they may result in significant morbidity and often require lifelong medical interventions; therefore, warrant discussion.