By Abhishek Jha:
You took copious notes in the classroom, return home with shoulders drooping, settle yourself on the sofa for some good old knuckle cracking, and tut! A parent’s wagging finger will inevitably point out that this is a bad habit. Any effort at countering this proscription is met with a health disclaimer: cracking knuckles causes arthritis.
This common wisdom, however, has little backing by researchers. From research papers published as early as 1975 to one as recently as 2010, and one that won an Ig Nobel Prize (it’s a thing), people have been unable to establish any relation between knuckle cracking and arthritis.
But there is a cracking sound, right? Yes, it is true that there is a cracking sound, but that is not because your bones are ‘cracking’. On the other hand, studies indicate that it has more to with a bubble burst in your joints. As it happens, your knuckle joints are surrounded by a membrane where a viscous fluid lubricates your joint. Now this fluid has some gases, which form bubbles when you stretch your joints. This bubble formation happens because the pressure in your joints is lowered when the joint is stretched. The explanation for bubble formation is beyond the scope of this article (but those interested in more exploration would know it as the magic of vapour pressure). As the joint-fluid flows into the space created by the stretched joint, these bubbles collapse making the characteristic cracking sound.
It takes about 15 minutes for the gases to mix again before you are able to repeat the procedure. Since there are other factors like the space between your joints also at play, it is also not necessary that a sound will be produced.
Yet, there is bubble cracking! That bubble burst can hurt the bones, no? Well, if it does, this does not lead to the wear and tear arthritis (known better as Osteoarthritis). Even the mean (the shady 1970s research concluded that its “annoying effect on the observer” is the only bad that knuckle cracking can do) habitual knuckle-crackers are not known to end up with Osteoarthritis due to bubbles bursting in their joints.
There is a catch however. A study published in 1990 says that habitual knuckle crackers have more swelling of the hand and lower grip strength. Sigh! Also, the cracking sound follows the pressure release that occurs (called articular release). This articular release requires that one overcome the physiologic barrier, which when crossed makes the joint move more freely. People trying too hard to get that sound are also known to have injured themselves.
Confusion galore! Thank you very much, researchers. What habitual knuckle crackers would probably want to know is whether they should abandon the habit. As far as arthritis is concerned, the word out there, as the studies show, is that you won’t get arthritis. Physiotherapists, however, say that a cracking sound with any associated pain should concern you. At any rate, never at least try to crack your way to an injury.