Choosing a functional brace for knee injury is a complex issue complicated by a lack of quantitative research on the subject and an increasing number of braces currently on the market. The correct brace decision will be facilitated by a better understanding of knee injury biomechanics and by a thorough understanding of the choices available. The ultimate selection of a brace should be based on sound mechanical criteria and individualized for each patient. The brace must be mechanically effectual and one the patient likes, has confidence in, and will tolerate. In combination with aggressive rehabilitation, the functional brace can make a significant contribution to returning individuals to functional activity.