Investigations into the gait of persons with partial foot amputation (PFA) suggest that the effective foot length can be restored when the prosthesis incorporates a relatively stiff forefoot, restricts dorsiflexion, and includes a mechanism whereby forces caused by loading the toe lever can be comfortably distributed to the leg (e.g., an anterior tibial shell). The purpose of this investigation was to systematically alter these variables to understand which design elements are responsible for restoration of the effective foot length. By manipulating features of the prosthesis design in two persons with PFA, we demonstrated using three-dimensional motion analysis that the prosthesis must incorporate each of these design elements to restore the effective foot length. When these design elements were used in concert, the persons with PFA adopted a gait pattern more consistent with nondisabled persons. Further work is required on a larger cohort to ensure the observations are generalizable.