A wearable device that records the sounds of knees cracking could reveal clues about the condition of the joint (Scientific American, 2016).

The device has been developed by Omer Inan, an electrical engineer at Georgia Tech, who said “I actually feel like there’s some real information in them that can be exploited for the purposes of helping people with rehab.”

His experience with cracking knees goes back to his days as an undergraduate at Stanford University, where he threw discus. He said “If I had a really hard workout, then the next day of course I’d be sore, but I’d also sometimes feel this catching or popping or creaking every now and then in my knee.”

Omer Inan, who built tiny microphones at a high-end audio company, before working at Georgia Tech, developed the device with a team of physiologists and engineers as part of a Defense Advanced Research Projects Agency (DARPA) project to develop better technology for knee injuries. The device uses tiny microphones strapped to the knee to monitor the sound of cartilage and bone rubbing together during movement. The researchers built a prototype with stretchy athletic tape and a few tiny mics and skin sensors. Preliminary tests on athletes suggest the squishy sounds the device picks up are more erratic, and irregular in an injured knee than in a healthy one, which Omer Inan said might allow patients and doctors to track healing after surgery. He said:

The primary application we’re targeting at first is to give people a decision aid during rehabilitation, following an acute knee injury, to help them understand when they can perform particular activities, and when they can move to different intensities of particular activities.

Further details of the project appear in the IEEE Transactions on Biomedical Engineering.