Prosthetic legs with sensors can help people avoid unseen obstacles underfoot. Three people who have had a leg amputated found that they perceived such prostheses as an extension of their own body and were able to climb stairs more quickly than they could with a conventional prosthetic leg. Prosthetic limbs are often abandoned due to people's poor mobility when using them. The devices don't restore sensation, leaving people to rely on touch feedback from the stump meeting the socket. Stanisa Raspopovic at the Swiss Federal Institute of Technology in Zurich and his colleagues modified a commercially available prosthetic leg by adding sensors to an insole on the foot and inside the knee.