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This is Scientific American's 60-second science. I'm Christopher in Taliatta.

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 Enan, 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.

But I would also sometimes feel that I would feel this basically catching or popping

or creaking every now and then in my knee.

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 bent?

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.

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