Do YOUR knees crack? Try listening to this! Excruciating video reveals the gruesome sounds our joints make every time they bend


  • Device uses microphone and sensors to record scraping joint sounds
  • As the man straightens his knee, a loud crunching sound can be heard
  • Scientists say this is the noise of bone or cartilage rubbing together 
  • Hoped the device will be used for research into causes of joint pain 

Kate Pickles For Mailonline

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It sounds like a familiar crunch from scrunching up paper or pulling off a stalk of celery.

But the snap and crackle heard in this ear-curdling video is actually the sound your knees make every time they bend.

A team of researchers have developed a device which records and amplifies the sound one of the most parts used parts of the body. 

Even people who think they have healthy knees will be horrified to listen to the grinding sounds their joints make when rubbing together.

And this is before the clicking and cracking people typically experience with age, which is audible to the naked ear.

The video starts with Professor Omer Inan getting back into the swing of his college days as discus thrower.

He spent years whirling around like a tornado, which he admits knees aren’t built for, during his time studying at Stanford University.

While lobbing the discus to demonstrate, he explains the sport – along with daily wear and tear from carrying weight – heaps strain on the knees.

The video then cuts to a patient who has had the listening device strapped to his knee.

As he moves it from bent to straight, his knee lets out a sound that’s so cringe-worthy, it makes even the most hardy, coil away in disgust.

But the man with the crunchy knee just sits there, clearly not in any pain.

The 1 minute 30 second clip is demonstrating the knee band, developed by engineers at the Georgia Institute of Technology.

The device uses microphones and vibration sensors to listen to and measure the sounds inside the joint. 

As the man straightens his knee, a toe-curling crunching sound can be heard – but it’s actually just the sound the joint makes every time it bends and straightens

 

When he heard the first recordings of crackly grinding in early experiments, Professor Inan was surprised by the extent of the sounds.

‘It was a lot louder than expected and a lot clearer,’ he said.

To others however, it just sounds grotesque. 

‘It’s a little bit like some kind of Halloween stuff happening. 

‘You’re listening to your bones rubbing on each other, or maybe cartilage,’ Professor Inan said.

Now researchers are using the device to graph out the recorded audio.

They match the pattern to the joint’s range of motion to see where exactly in the leg’s extending and bending, the knee creates creaks and pops.

The result has peaks and squiggles that resemble an electrocardiogram or other physiological signal.

Early results note the acoustic pattern an injured knee produces is markedly different from that of an intact knee. 

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

It is now hoped medical research will build on the acoustical sensing technology, which doctors called ‘crepitus’ and eventually decode the sound into useful patterns to study joint pain. 

They study and accompanying video was published in the journal IEEE Transactions on Biomedical Engineering online. 

 

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