Physical Pursuits

Physical Pursuits - Bioengineering

The Jaipur Knee, a low-cost prosthetic knee joint, is comprised of five pieces of plastic and four nuts and bolts. It requires no special tools and takes just a few hours to manufacture.

One of the greatest gifts of mechanical engineering is how it has helped design prosthetics to improve physical mobility and dexterity. Joel Sadler, a former Stanford University lecturer in mechanical engineering, found that the biggest challenge isn't just innovation, but budgeting.

"You have to focus on improvement but also on how many people already go without technology that already exists," he says. One of the inventors of the Jaipur Knee, he and his team set out to create a knee joint prosthetic for $20 for the world's less fortunate. With more than 3,000 on the receiving end thus far, it's changed the lives of people who otherwise would never get the mobility so many of us take for granted.

Physical Pursuits - Bioengineering

Co-Inventors Eric Thorsell and Joel Sadler with Kamal, a young amputee from India.

"The cutting edge bionic knee or hand are $20,000 - $25,000 just for the components," says the native of Kingston, Jamaica. "Add all the costs up like a car where you want extras and it could be more than $100,000 for a top-end system." These kinds of numbers are clearly not easy to afford and also require large sums for testing. Sadler even reminds that those opportunities usually come with a far different price. "The biggest leaps in innovations and investment happened after wars," he says. "Because the need is suddenly there [for soldiers]. But what also amazes me is how the old inventions of prosthetics still hold up. The device used for hands, the split hook, hasn't changed that much."

Beyond All of Us

Sadler says the innovation trend will not be continued as a result of trying for everyday function only, but believes there will be a leap toward augmenting functions. "It's not just helping someone missing limbs," he says. "It's about people who want to go beyond the natural limits of human characteristics like strength, dexterity, and reducing the tendency to be injured.

"We're talking about what's been going on with the idea of recreational bionics for troops walking on uneven terrain carrying superhuman heavy loads," he says. "Or Cyberdyne with human-assisted lifting. It will even eventually come down more to putting things over the exoskeleton and figuring out how to get a mechanical interface over our squishy human bodies."

Physical Pursuits - Bioengineering

Close-up of the polycentric design made of hard plastic.

But one thing Sadler says is likely never to change is how patience is needed for success. "For Jaipur, we loaded 700 pounds of other components, we did a cycle load 4 million times, equivalent to four years of walking. Even after its results and low cost, there are still many we haven't gotten to. Many people think of trying to make something work but not about the long haul."

In fact, it's a haul that could be the greatest impediment to future demand for prosthetics. "There are people all over the world who suffer and need these items but a key principle of business is distribution," he says. "You have poor countries that need prosthetics badly and two [customers] could live many miles from each other in a very rural area. How do you service all of them and still turn a good profit? The person who solves that is just as important to the future of prosthetics as anyone."

Eric Butterman is an independent writer.

The cutting edge bionic knee or hand are $20,000 - $25,000 just for the components. Add all the costs up like a car where you want extras and it could be more than $100,000 for a top-end system.

Joel Sadler, former lecturer, Stanford University


January 2012

by Eric Butterman,