One promising approach is to reuse impact energy by incorporating elastic elements. As there is a lot of potential for that around the ankle joint, numerous engery conserving prosthetic feet are commercially available.

Another factor is correct alignment of the prosthesis. If the prosthesis is too stable, the user has to use excessive energy to overcome the stability point and initiate swing phase. If it is too dynamic, the user has to actively stabilize the leg using his hip muscles, which leads to an increase in metabolic load.

Finding the sweet spot of prosthetic alignment is a key factor for energy reduction.

Implanting an Endo-Exo Prothesis into the femur will give you back control and a sort of sensitivity for the ground.

Thanks for your answer Mr. Roland Auberger