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Comment by morganvachon | Hacker News Reader

Very interesting. In my "old age" (38 next month) I've found that my ankles and knees have begun popping or cracking with regularity. I can rotate my right foot in a circular motion and it will pop just below the top of the ankle on every single downstroke no matter how many times I do it. My knees have begun popping every time I stand up and usually when I stretch them out under a desk or table. Five years ago this didn't happen, and I'm actually more active today than I was back then.

I've often wondered if the "gas bubble" theory was only partially correct, as there are different kinds of pops and cracks with different sounds and sensations (including pain).

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> I can rotate my right foot in a circular motion and it will pop just below the top of the ankle on every single downstroke no matter how many times I do it.

I've been doing that, also with my right foot, since high school.

Me too! I thank the fact I played basketball since I was in 3rd grade.

My ankle does the exact same. My understanding is that for this sort of cracking, where there is no "refractory period" between cracks, the gas bubble thing is not the cause. Rather it might be a tendon "snapping" across a bone, like some sort of bistable system.

I also have another sort of cracking where the refractory period is weeks, rather than ~20 minutes. I suspect this is another phenomenon as well, though I don't know what it might be. I experience this in my wrists, sometimes sternum (perhaps snapping cartilage in the xiphoid process? I really try to avoid this one.)

My elbows also crack when I hyperextend them. The refractory period there is probably somewhere between 20 minutes and an hour, but I'm not convinced that is the gas bubble thing either.

I pop my knuckles, all 3 thumb joints, wrists (by pronation of hand and supination of forearms, or vice versa), elbows (by hyperextension), shoulders, and cervical vertebrae on a regular basis, and occasionally thoracic vertebrae, toes, and hips. I can very rarely manage to pop one knee or the other, or lumbar vertebrae. I have never been able to pop anything in my ankle; there's just too much joint stabilization there. But I can manage the metatarsal-cuboid joints sometimes by twisting the foot from the toes.

If you can snap your ankle every time you move it in a particular way, it is probably not the same thing. I have never been able to pop the same joint twice in rapid succession. Indeed, that's why I pop so many different joints. Once you've done them all, there's no choice but to wait.

I'd certainly be wary of pops emanating from joints without a great deal of natural range of motion, or those so wrapped up in muscles and ligaments it is practically impossible to isolate any one joint in particular. If you experience any pain while joint-popping, stop doing it, immediately.

Wow, how did you manage to do the thoracic vertebrae? I have been trying to achieve that one for years! On the plus side, I was able to master repeated ankle cracking without refractory period - So I haven't exactly wasted my life.

There are two reliable ways to do it. First, you cross your arms over your chest and put your hands on the opposite shoulders. A brawny accomplice then stands behind you and picks you up by your elbows. Your spine is stretched by your own body weight and your accomplice's chest. That is truly satisfying, but I haven't had it done in many years.

Second method, you put your back against a hard, flat surface and push yourself into it. This one may only pop one or two at a time. And you might break your furniture.

In my old age also (36), one of my ankles pops every time going up (not down) stairs. I also, crack my knuckles, fingers, neck numerous times throughout the day. It's more of a habit now, versus "feeling" anything.

I'd love to know, in laymans terms, the repercussions to doing this. As far as I could gather from the article, it doesn't sound like any long-term effects.

One other question I have, though, is why is it "easier" to crack these parts over time? The more I do it, the easier it is to repeat in the future. Am I just creating this space, and making it easier to "fill" with every "distraction", as the article called it?

There was an Ig Nobel winner who did some work on this[1]. A doctor that cracked the knuckled on one hand and one hand only for decades, and found no discernible difference.

1: http://www.scientificamerican.com/article/crack-research/

Dr. Donald Unger won the 2009 Ig Nobel for demonstrating (N=1) that knuckle-cracking doesn't lead to arthritis, by cracking the knuckles of one hand daily for 60 years, and never cracking those of the other.

http://tech.mit.edu/V129/N41/ignobels.html

Like I said, for someone that does this NUMEROUS times a day, that is some EXTREME self-control to be able to only do it to one hand that long.

When I don't crack my knuckles regularly, they start to feel extremely stiff and experience a dull pain. There is no way I'd be able to stop myself from cracking one of my hands for that long. That really is extraordinary self-control.

There is some evidence that lack of sideways flexibility in the joints contributes to synovitis in climbers. A common recommendation is to regularly twist and stretch the finger joints like this https://www.youtube.com/watch?v=IMO__OrzM_U . Perhaps cracking the joints has a similar effect.

Something that might be enlightening: taking an mucokinetic—a drug that increases and dilutes mucus, e.g. guaifenesin—increases cracking. Presumably sinovial fluid qualifies as "mucus."

Neat, my right ankle has also done that for years, but on the top of the upstroke! It's done it for years, though lately my left ankle also does it. (I'm 30) once again the internet brings together the mutants that once believed themselves alone.

this started for me at 14 :( i feel old

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