This is scientific American's 60 second science. I'm Christopher in Tagata.

The sound of a cracking knee isn't particularly pleasant, but it gets worse when you listen up close.

It does for most people, but for me it's, it actually just makes me excited.

Omar Enon, an electrical engineer at Georgia Tech.

I actually feel like there's some real information in them that can be exploited for the purposes of helping people with rehab.

Enon's experience with cracking knees goes back to his days as an undergrad at Stanford, where he threw

discus.

If I had a really hard workout, then the next day, of course, I'd be sore sore but I would also sometimes feel that I

wouldn't feel this basically catching or popping or creaking every now and then in

my knee. A few years later he found himself building tiny microphones at a high-end audio company.

So when he got to Georgia Tech and heard the Defense Advanced Research Projects Agency,

or DARPA, wanted better tech for knee injuries? He thought,

why not strap tiny microphones to people's knees,

to eavesdrop as their legs bend?

What we think it is, is the cartilage and bone rubbing against each other, the surfaces inside the knee

rubbing against each other during those movements.

He and a team of physiologists and engineers built a prototype with stretchy athletic tape

and a few tiny mics and skin sensors.

And preliminary tests on athletes suggest the squishy sounds the device picks up are more erratic

and more irregular in an injured knee than in a healthy one, which Enon says might allow patients

and doctors to track healing after surgery. Details appear in the I-triplee transactions on

biomedical engineering.

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