Tensegrity, a prototype prosthesis, offers the wearer a stable gait thanks to its reproduction of the human foot's natural mechanisms. From Medgadget:
Built by inventor and mechanical engineer Jerome Rifkin, the artificial foot bends like a normal foot and ankle, and conforms to the terrain underneath it. The prosthetic options for foot amputees is limited due to the complexity involved in mimicking the weight-bearing action and propulsion involved with the foot.
While fancy robotic prosthetic feet are already available, insurers don't like them and won't pay for them. Tensegrity, however, doesn't use complex, vulnerable electronics: it's pure hardware, manipulated with thick braided metal ropes and pneumatics, with no need for expensive motors, regenerative power cycling or AI chips.
"The human foot is ... a passive device. You just have to set it up correctly and let it do what it does," Rifkin told Popular Science, which reports that it cost $100,000 and eight years to develop. It has video of it in action.
A more natural prosthetic foot [Medgadget]
The Natural Artificial Foot [PopSci]