Snap Crackle Pop: Yea That Was My Knee (Part 1)
I hear these two sentences a lot:
"Every time I stand up from the couch or climb stairs that knee just pops and clicks and makes all kinds of racket. It must really be worn down."
or
"Yea those first few warm up sets on squat I normally get a pretty loud pop out of that knee. It doesn't hurt, it just always happens."
Scientist and Doctors lump these sounds into one term and call it crepitus. That's the last time I'll use that word since we aren't here to learn about fancy words. We are here to help you understand more about why your knee(s) pop and if/when it could be concerning.
Lets start with putting these noises into two categories.
1. It's probably normal
and
2. Probably need to get that looked at
1. It's Probably Normal
The Loud Pop: This is the loud one time pop you hear. You do it once and you cant make it happen again until some time has past by. I also lied earlier when I said no more big words because here it is, tribonucleation. It is the process of when two solids are separated from one another, when submerged in a liquid, can produce small gas bubbles.
And guess what, it happens in the human body. It is a normal body process and to this date, the best evidence I can provide to explain why you hear a loud pop. What happens is when you get up or squat down there is slight separation of the two bones that make up your knee joint. In that joint you have fluid. When you bend your knee a certain amount or squat down there can be just enough force and joint separation to allow for these small bubbles to form. If it happens quick enough, we get a pop that we can hear.
On an MRI what is seen as this occurs a change in color of the image between the joint surfaces after the audible pop. Before the joint surfaces separate they show fluid, which is a different color than air/gas. Right after the separation of the joint surface the image now shows an area of color that shows an air/gas cavity. After the pop there is a time period after in which it takes for the gas to disperse into the joint fluid. And that is why after you pop it, you can't do it again for an amount of time.
The closest example to the knee where this has been seen is in the fingers. I'm sure you have pulled your finger or bent it in a way where it pops. It may catch you off guard, but it doesn't hurt. Oh and "poppin' ya knuckles" doesn't cause arthritis in your hands (that's for another day).
In part 2 we will look at other sounds (What, you can't see sounds?) that are pretty normal and shouldn't be a cause for concern.
P.S. Don't tell your Mom to back off because I said it was okay to pop your knuckles. What mom says goes, no matter what science says.