The goal of modern prosthetics is to replicate the function of the replaced limb or organ in the most capable and discreet fashion possible. However, even the most advanced, commercial, transtibial prostheses available today only passively adjust the position of the ankle during the swing phase of gait and return a portion of the user's own gravitational input. To greatly improve the quality of life of a transtibial amputee, new technologies and approaches must be used to create a cutting-edge robotic ankle prosthesis which can perform on par with, if not outperform, the equivalent able-bodied human ankle. Initial attempts by us and others have had great success in providing the natural gait power and motion through all ranges of walking speeds. A new design is presented which governs both the coronal and sagittal angles and moments of the ankle joint to potentially provide unprecedented levels of athleticism and agility among transtibial amputees.