The study population will include sixty (60) children with idiopathic scoliosis who will undergo spine surgery and sixty (60) developing children "Control Group". Scoliosis patients will undergo a period of testing which requires three visits: pre-operative evaluation, one-year post-operative evaluation, and two-year post-operative evaluation. The Control Group will require one initial assessment. A total of 240 evaluations will be performed over a three-year period. We will evaluate the correlation among outcome tools and quantitative measures in order to determine how these instruments can be used more effectively for better treatment. Subjects and their parents will be fully informed of the nature of the study as well as the potential risk involved and sign the appropriate consent form. The study will be reviewed by the IRB and include HIPAA compliance. This will be accomplished during testing at the Shriners Hospital for Children- Chicago Motion Analysis Lab. All possible steps will be taken to assure the safety and convenience of the study participants. All subjects will be evaluated using clinical outcome tools (PODCI, SF-36) and will undergo quantitative 3-D motion analysis and postural stability assessment. Quantitative 3-D gait analysis will be done with our 14-camera Motion Capture system and passive reflective markers (Figure 3). Motion analysis will be performed with each subject walking at a comfortable and natural speed on the laboratory walkway. Passive markers will be attached to anatomic landmarks in standardized locations using double-backed tape. Marker coordinate data will be used to determine range of motion and joint angles.