Assessments of children with Osteogenesis Imperfecta (OI) are typically limited to a physical exam and observations from a clinician during a hospital visit. Often quantitative information such as bone mineral density and outcome questionnaires is obtained, but with the increasing prevalence of motion analysis and other performance type laboratories, there are many other tools available, which could be beneficial to this patient population. These laboratories can provide date supplementary to morphologic and radiographic data that is helpful in tracking changes in the patient’s functional abilities, recover from fracture, and treatment outcomes. This chapter will cover some useful evaluation methods for children with the most commonly seen types of OI and provide some examples of their test results