Magnetic Knees

It's fairly easy nowadays to grow knee stem cells in the lab to repair or replace cartilage, but once those cells are placed in a worn-away area of a joint, it's hard to get them to work—they tend to spread throughout the joint. So Japanese researchers incorporated a magnetized iron oxide molecule into stem cells and surgically inserted a magnet under the injured portion of a rat's knee. Like magic, the stem cells moved into place immediately and were continuing to build new cartilage there three months later.

How Soon: A variation of this approach could be available in a few years. In the future, researchers may develop a magnet that would dissolve in the body over time.

Bionic Ankles

To date, prosthetic limbs haven't been good at understanding messages from the nervous system—which means they haven't been able to fully integrate with the body and brain. But in April, scientists at the Rehabilitation Institute of Chicago reported that they'd programmed a computer to recognize muscle signals from amputees' intact upper legs. When the volunteers flexed their leg muscles, electrodes attached to their skin picked up electrical activity and fed it into the computer, which then translated the signals to move virtual knees and ankles portrayed on a screen. After a few tries, the amputees were bending their onscreen knees and twirling their onscreen ankles with ease.

How Soon: The scientists hope to test computerized prosthetics in the lab within a year, and outside on streets and stairs in about three years.

Better Ankles

To treat an arthritic ankle, surgeons often fuse the joint, which can limit a person's ability to run, climb stairs, and play sports. But the FDA recently okayed a new generation of artificial ankles that more closely mimic nature's shifting, wobble-stabilizing originals. Studies show that the joints allow for more natural movement than fused ankles, though their long-term safety isn't yet known. (More on that in about six years.)

How Soon: The prosthetic joints are already being used as ankle replacements today.

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