You probably wouldn't try using the same motorbike for both racing over rough trails and commuting on smooth roads, so ... why use the same prosthetic leg? That's the thinking behind the Moto Knee, a prosthesis that's designed for activities such as skiing, horseback riding, cycling and motocross. In order to withstand the impacts that come with such activities, it even incorporates a Fox DHX Air mountain bike shock absorber.

The Moto Knee was designed by motocross and snocross racer Mike Schultz, who lost his left leg in a snowmobiling accident. He soon got impatient with the limitations that a conventional artificial leg placed on his performance, so he set about designing his own "extreme" prosthesis.

"One of the main things that helped me understand how to start a project like the Moto Knee was my hands-on experience working on my racing equipment," he told us. "I was always trying to understand how to make my suspension components work better and understand exactly how and why they worked the way they did. Additionally, as a result of being an athlete and working with trainers and orthopedic doctors, I really understand body mechanics."

Moto Knee inventor Mike Schultz

Generally speaking, the Moto Knee is designed for any high-impact sport that requires what Schultz describes as "an athletic stance." The resistance ratio of its linkage system can be adjusted through its full range of motion, while the compression, rebound and damping of the Fox shock can also be set to the demands of the user and activity. The linkage and shock additionally work together to limit the amount of impact transmitted into the residual limb, and to keep the user's body mechanics laterally balanced.

Although the Moto Knee can be used with just about any prosthetic foot, Schultz designed one that's specifically suited to it, known as the Versa Foot. "As the Moto Knee bends, the ankle of the Versa Foot flexes much more than a typical prosthetic foot which allows you to keep much more of the foot sole on the ground through the 'squatting' motion – and this makes your stance considerably more stable," he explained.

In the same way that a performance off-road bike isn't ideal for city streets, however, the Moto Knee isn't designed for everyday walking. "To have a single knee system work really well for both walking and extreme sports would be very challenging," said Mike. "At this point the Moto Knee is specifically a sport knee and isn’t the best option for day-to-day walking since it doesn’t 'swing' like a normal walking leg."

The MotoKnee was commercially launched in 2011, with over 100 units having been sold since then. The Versa Foot was released a little over a year ago, and is approaching a similar sales number. The former costs approximately US$6,000, while the pricing for the latter starts at $2,300.

"I know what it was like to have my quality of life – my lifestyle – taken away because of my leg injury that led to amputation," Schultz told us. "I also know that incredible feeling of returning to the sports I loved most ... I want to share that feeling with others and allow them to return to the activities and lifestyles they had before their amputations, or for some, to be able to try different things for the first time and set new goals."

The Moto Knee and Versa Foot can be seen in use in the video below.

Product page: Biodapt

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