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There’s a Medical Term for That Cracking Sound Your Knees Make

Snap, crackle, pop, ugh

In 1915, physician and pioneering medical columnist Dr. William Brady was queried about the niggling issue of popping and cracking originating in the knee region of a concerned questioner. “I am troubled with my knees cracking when I go down stairs,” asked the worried writer. “What can I do? Is it old age coming on? I’m only 45.”

Brady minced no words in delivering his response. “Not old age,” he replied. “Perhaps the effect of past inflammation or injury of the knees. Do nothing.”

Brady’s answer was simple enough for its era, but was it sufficient? With more than a century to further explore the factors that can cause a normal human’s knees to echo like a milk-enhanced bowl of Rice Krispies, is there more to the explanation for the noises? And better yet, is there anything we can do to silence them?

I’m not comfortable having knees that sound like breakfast cereal. Is there something I can do about the noise?

It may surprise you to learn this, but that noise actually has a name — “crepitus” refers to any popping or grating noises that originate in one of your body’s joints. This unfortunate sounding word is sure to remind several people of the word “decrepit,” which literally means “elderly and infirm.” All of which is to say, knowing the technical name of the unsettling sounds that are causing you to face your own mortality is bound to have you associating those noises with old age.

Crepitus most commonly occurs when air bubbles develop in your joints, the same way air bubbles form in your esophagus before you belch. So if it makes you feel less like an old codger and more like a carefree college kid, you can think of crepitus as the burping that your knees perform when air gets trapped within them.

This sounds too simple. Are you sure there’s no other cause for crepitus?

Well, again, crepitus is merely the name of any noise that emanates from any joint. Remember when you annoyed your mother by repeatedly popping your knuckles at the kitchen table, even after she told you it would make your knuckles bigger if you kept it up? Okay, maybe that only happened in my household. Either way, those knuckle popping sounds are also crepitus. 

This also means that popping noises produced by more detrimental and painful (but far rarer) causes are also crepitus. These causes include both arthritis and tendon snapping, which can be undeniably uncomfortable. So if pain accompanies your crepitus, you should get it evaluated by a doctor. Otherwise, it is, in fact, just air escaping from your joint. You can feel free to ignore it, you can take steps to silence your knees (even though those steps are likely to be unnecessary), or you can embrace the sounds and turn your knee into a musical instrument.

Very funny. So I honestly shouldn’t be concerned as long as I don’t feel pain?

If you don’t feel any pain, there’s genuinely no cause for concern. Of course, there are plenty of folks who would love to capitalize on your paranoia, monetize it, and convert it into cash. In fact, many a chiropractor has made an extremely healthy living off of crepitus because their clients regard the series of sequential popping noises that accompany spinal adjustments to be the surest evidence of beneficial bodily realignments. While the legitimacy of chiropractic medicine remains a deeply debated topic, for some people, simply listening to the creaks and cracks of crepitus as the air escapes from their joints makes the whole experience worth the price tag.

It’s unfortunate that every noise linked with air escaping from your body can’t be as humorous as those produced within your rectum, but at least the sounds promulgated from your knees won’t be accompanied by malodorous smells. If they are, you should call a doctor — and the local news, because something very special is brewing within your body.