A knee band from the Georgia Institute of Technology uses microphones and vibration sensors to listen to and measure the sounds inside the joint. The sounds will help doctors determine whether a convalescing joint is healthy or requires more therapy.

Omer Inan, assistant professor of electrical and computer engineering, had suffered knee pain himself and would often feel the creaking and popping of his knee as he placed more stress on it.

Inan, developer of the knee monitor, hopes that acoustical sensing technology will decode the sound into useful patterns.

Inan and researchers are currently graphing out the recorded audio and matching it to the joint’s range of motion, examining where exactly in the leg’s extending and bending the knee creates creaks and pops. The result features peaks and squiggles that resemble an electrocardiogram or other physiological signal.

The acoustic pattern an injured knee produces is markedly different from that of an intact knee.

“It’s more erratic,” Inan said. “A healthy knee produces a more consistent pattern of noises.”

To create the acoustic device, Inan and the Georgia Institute of Technology researchers combined micro-electromechanical systems (MEMs) microphones with piezoelectric film. The film, a hypersensitive vibration sensor, collects the best sound, but is very sensitive to interference. The microphones placed against the skin make for an ample backup and a more practical device.

If paired with medical research, Inan’s acoustic device could lead to inexpensive, wearable monitors.