The purpose of this project is to create an affordable, state-of-the-art lower extremity orthotic device prescription system, called MOPS, that interactively guides the clinician in the decision- making process of prescribing an ankle-foot orthoses (AFO) and/or knee ankle foot orthoses (KAFOs). MOPS includes a set of pre-fabricated, adjustable, modular trial orthoses, and an interactive and instructional decision-tree software application that guides the clinician in selecting the most appropriate AFO/KAFO design and settings. An algorithm assists the clinician and patient with fine-tuning adjustments to the orthosis settings and any necessary modifications to the shoe to optimize walking function. To determine if the modular trial orthosis mimics the performance of the orthosis prescribed to the patient, it is compared with the gait performance of adult participants walking with the prototype trial orthosis and the patients own final custom- molded hybrid (plastic and metal) or metal orthosis (with static or dynamic joints), as well as with no orthosis. The project evaluates the outcome of the orthotic prescription with MOPS through patient and clinician satisfaction surveys and a series of focus groups.