A prototype of prosthetic knee that mimics normal walking motion has been designed by researchers at Massachusetts Institute of Technology (MIT). After successful initial results its prototype will be tested in India.
The team has built the prototype of a prosthetic knee that generates a torque profile similar to that of able-bodied knees, using only simple mechanical elements like springs and dampers.
The prototype will be tested in India, where about 230,000 above-knee amputees currently live. The invention has the potential to revolutionize the prosthetic limb industry as good prosthetics cost several thousand dollars.
For instance, a top-of-the-line prosthetic -- that incorporates microprocessors which work with on-board gyroscopes, accelerometers, and hydraulics to enable a person walk with a normal gait -- can cost around $50,000.
Amos Winter, an assistant professor of mechanical engineering at MIT, said his team has developed a passive, low-tech prosthetic knee that performs nearly as well as high-end prosthetics, at a fraction of the cost.
"If we can make a knee that delivers similar performance to a $50,000 knee for a few hundred dollars, that's a game-changer. In places like India, there's still stigma associated with this disability. They may be less likely to get a job or get married. People want to be incognito if they can," he added.
Most amputees in developing countries wear passive prostheses -- simple, cheap designs with no moving parts. "When you see people walk in them, they have a pretty distinctive limp," Winter said.
In part, that's because passive prostheses do not adjust the amount of torque exerted as a person walks. For instance, in normal walking, the knee flexes slightly, just before the foot pushes off the ground -- a shift in torque that keeps a person's center of mass steady.
In contrast, a stiff, unbending prosthetic knee would cause a person to bob up and down with each step. The researchers used the measurements to calculate a torque profile -- the amount of torque generated by the knee during normal walking.
"Our challenge was, how do you tune the torque profile to get able-bodied motion, with a passive prosthetic knee. This was a quick prototype, but so far, we are seeing good indicators of natural gait," Winter said.
The finding was reported in IEEE Transactions on Neural Systems and Rehabilitation Engineering.