Sixteen individuals with Costello syndrome underwent a complete history, physical examination, and medical record review. Medical history and record review were performed for two additional children with Costello syndrome. The POSNA Functional Health Outcome Questionnaire Baseline Assessment was completed by the parents of all 18 children. All the children were below the fifth percentile for height and all had ligamentous laxity. All children demonstrated delayed walking and none was able to run. Orthopaedic problems included tight heel cords, congenital vertical talus, planovalgus feet, hip subluxation, kyphosis, scoliosis, radial head subluxation, elbow flexion deformity, reduced shoulder range of motion, and limitation of overhead activity. Foot problems were most frequently encountered. Two children had no orthopaedic symptoms. All children with Costello syndrome had poor scores on the POSNA Functional Health Outcome Questionnaire. Orthopaedic problems are a significant part of Costello syndrome, and affected individuals should be evaluated and followed-up regularly by an orthopaedic surgeon.