Background Rotationplasty may be indicated for some children with osteosarcoma in the distal femur or proximal tibia; in properly selected patients, it may offer functional advantages over transfemoral amputation and more durable results than a prosthesis. The clinical and functional outcomes reported for this procedure generally have been limited to studies with a mean followup of approximately 8 years in terms of Musculoskeletal Tumor Society Score (MSTS), physical examination, and gait analysis. However, the effects of residual thigh-shank length on gait have not been explored to our knowledge. Questions/purposes We asked: (1) Do differences in the length of the surgically treated residual thigh-shank relative to the contralateral thigh result in altered gait patterns? (2) What were the clinical and functional impairments and radiographic findings of patients who underwent rotationplasty and who survived to adulthood? (3) Do gait analysis findings in adults differ from previously reported findings in children in terms of relevant gait parameters such as maximal ground reaction forces and sagittal knee angles? Methods From January 1986 to December 2009, 254 children (age range, 3-14 years) affected by high-grade bone sarcomas located in the distal half of the femur were surgically treated at our institute. Forty-two of these patients (16.5%) underwent rotationplasty. During this period, three adolescents older than 15 years were treated by rotationplasty owing to the tumor volume and extracompartmental involvement. In total, 45 patients underwent rotationplasty. From January 1986 to December 2000, rotationplasty generally was the preferred treatment for patients younger than 9 years with a high-grade bone sarcoma calling for an intra-or extraarticular resection of the distal femur, as long as the sciatic nerve could be spared. From January 2001, the procedure was not used as often. Of the 45 patients who underwent a rotationplasty, 14 died of disease at a mean of 37 months (31%); 31 patients (69%) were survivors at the time the study was done, 29 of whom were continuously disease free (64%) and two had no evidence of disease after a pulmonary metastasectomy (5%). These 31 patients were invited to participate in the study, and 25 of the 31 agreed to participate. There were 15 males and 10 females with a mean age of 23.8 years (SD, 7.5 years) and mean followup of 15 years (SD, 5.8 years). Clinical assessment included the MSTS score (total score ranges between 0 and 30 with 0 Each author certifies that he or she, or a member of his or her immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research 1 editors and board members are on file with the publication and can be viewed on request. Clinical Orthopaedics and Related Research 1 neither advo...