cracking knuckles during dive?

[DavidNedved]

Hi All,

I remember from biology class that doctors at the time were not sure what caused an individual's knuckle's to crack. They were apparently divided on whether it was nitrogen bubbles popping, or connective tissue sliding around and popping. Well, I've decided for myself that mine certainly pop due to nitrogen bubbles. When I'm doing ascents, my knuckles always crack at least once or twice. I'm mostly wondering whether anyone else has ever noticed this? It doesn't bother me in the slightest, but since I've never heard anyone else mention it, I wonder if it means anything odd about my physiology? Just one of those weird things that I thought you guys / gals might be interested in discussing or have something to add... anyone else notice this?

 

[Dr Deco]

Dear David:

Knuckle Cracking

This is something that not everyone can do. In this category, we also find cracking the spine and neck. This is the result of the rapid formation of a gas phase (bubble of nitrogen, oxygen, carbon dioxide and water vapor) within the synovial fluid of the joint. When surface are separated, there is a low-pressure region formed. If the tensile force is great enough, eventually a gas phase will appear. This collapses and a sound is heard (that is one explanation, anyhow). A period is required for the last of the gas phase to shrink down before the joint once again can be “cracked.”

Unsworth A, Dowson D, Wright V. 'Cracking joints'. A bioengineering study of cavitation in the metacarpophalangeal joint. Ann Rheum Dis. 1971 Jul; 30(4): 348-58.

This can also occur between the disks of the spine, and it is referred to as the vacuum phenomenon.

Viscous adhesion

This is a variation of the process known as “viscous adhesion” and is probably responsible for the formation of micronuclei in the capillaries (see attachment). The same process is responsible for the clicking sound that one can make with their tongue on the hard pallet of their mouth.

Dr Deco :doctor:

 

[JDostal]

So would it be a bad thing to crack your knuckles while you are diving? My knuckles crack very easily, and I often do it without even realize that I am doing it.

Would cracking knuckles at depth (which I have occasionally caught myself doing) have any ill effects?

 

[Dr Deco]

Dear Omicron:

Cracking your knuckles should not really cause any problems. A free gas phase in the joint itself is not associated with any pain or problem.

I did hear of someone who could crack his spine. Exactly how he did this, I do not know. People crack their neck, toes, whatever! The fellow became paralyzed immediately, however. He did recover with recompression - happy ending.

Dr Deco :doctor:

 

[JDostal]

Well thank you very much for alleviating the concern for me Dr. Deco. I didn't think it was too much of a big deal, but I figured as long as the discussion was going I should ask. It's a hard habit to stop - I've been doing it for so long I don't even realize I do it anymore, and my fingers always seem to feel more limber after doing it.

 

[Dr Deco]

Dear Omicron:

Curiously enough, when commercial divers are rapidly compressed (about 60 feet/min) to beyond 500 fsw, they find that their joints feel stiff. Scientists termed this "hyperbaric arthralgia", but they call this “no joint juice” as if the problem was one of lubrication.

Some test subjects tried to “crack” their knuckles at 1,000 fsw during a hyperbaric chamber study. If I remember correctly (it was in 1973), they found that it was not easy to do at this depth.

Dr Deco :doctor: