Georgia Tech researchers say knee sounds reveal secrets about joint health

Many of us have knees that crackle, or pop or even crunch. But what do those sounds really mean?

Georgia Tech Associate Professor of Electrical and Computer Engineering Omer Inan and his team are listening closely. Because, Inan says, the subtle vibrations and sounds our knees make call reveal a lot about their health.

"The knee is made up of soft tissue, and it holds up all of our body weight, and it has to do all kinds of crazy things when we're trying to do things like jump or run or sprint," Inan says. "When it does so, these tissues rub against each other."

To record the sounds made by that friction, Inan and his team have designed wearable knee sensor mounted with tiny microphones about the size of the head of a pencil.    

"Before our group, people would try and measure this and they would take these giant microphones and push them against people knees," he says.

Inan says that was not really practical. So, they made their sensor as portable as possible, testing it Georgia Tech athletes, to record the sounds their knees made during workouts.

"If your knee does have an injury, it sounds different," Inan says.

The team translates the audio recordings into graphs that are similar to what you would see on an EKG.
A healthy knee makes an even crackling noise as it moves. But, if you listen to recordings of an injured knee, the sound is less even and more erratic.

Inan says they have been able to tease out what each sound means.
So, he says, the device may one day be helpful in assessing players who are injured on the field.

"You want to understand, should we take them out of the game," Inan asks.

If we do get injured, monitoring our knee sounds could one day tell us when it's safe to exercise again,
or when we need more time to recover.

The clues are there, Inan says. We just have to listen for them.