Imagine the snaps, crackles and pops of a crispy cereal or the sound of a potato chip bag being crumpled. Each time you move your lower limbs, those are the sounds your knees make on the inside, even without you realizing it.
Now, researchers are hoping to put those cringe-worthy sounds to good use, harnessing them to track the health of patients.
Engineers at the Georgia Institute of Technologyhave developed a knee band equipped with tiny microphones and sensors that can record the noises our knees make and deliver those recordings electronically to doctors.
Doctors then can listen to those recordings to pinpoint noticeable changes in the sounds, which could help them evaluate damage after a knee injury and track improvements or setbacks in recovery, said Omer Inan, an assistant professor at Georgia Tech who has led research on the new knee band technology.
“We would not want to look at a snapshot of the sounds and try to diagnose if someone has a particular injury. But what we are interested in is looking at a person who already has been diagnosed and then tracking them over time to see if they’re getting better or worse,” Inan said.
“If an injured person performs exactly the same knee flexion-extension exercise, their knees may produce very different sounds each time,” he said. “Whereas, for a healthy person, if they perform the same exercise, we would see very similar signatures. It’s very consistent in nature.”
Overall, Inan pointed out that a healthy knee without a history of injury tends to sound softer than a knee with a history of injury, which sounds more static-y or crackly.
Knee injuries are common in the military as well as in sports, Inan said. Using sounds to assess the recovery of a soldier’s or an athlete’s knee could be helpful in deciding when that soldier should return to duty or that athlete should return to competition, he said.
“What we’d like to deliver to a doctor is a health score for the patient, so that score could be something as simple as a red, green and yellow indicator and could then be used by that patient to determine when they can move to different types of exercises during rehab, when they might be able to return to their sport and when they should really back off and maybe work on some more basic exercises to get their knee better,” Inan said.
To pair a knee sound with a certain stage in injury recovery, Inan and his colleagues simulated injury and swelling stages in cadaver knees, he said. To simulate swelling, for instance, they put various amounts of saline into the knee capsule and then recorded what sounds that knee produced.