Is Cracking Your Knuckles Good or Bad?

Is Cracking your knuckles good or bad? This seems like one of the oldest questions of human kind almost on par with: “Which came first, the chicken or the egg? We have all had a friend, or family member tell you that cracking your knuckles will give you arthritis.

I have had patients, friends and family members ask if cracking your knuckles is good or bad. The simple answer to this question is it is good for the joint. All synovial joints of the human body, from your fingers, your spine, all the way to your toes will crack or pop naturally. For those who don’t know, a synovial joint is where two bones meet and have a fluid filled joint space between them. This is then surrounded by ligaments forming the joint capsule, which both strengthens the joint and encapsulates the fluid within the joint space.

What’s the Crack?

The cracking or popping sound the occurs during either normal joint motion or during spinal manipulative therapy of chiropractic adjustments are technically called a cavitation. A cavitation in physics is a rapid change in fluid pressure. This change in fluid pressures the formation of an air bubble within the fluid. This process of cavitation is the same process as a ship or boats propeller blade moving through water. When viewed from below the water, the propeller blade causes bubbles to form within the water as the boat moves through it. This process is shown in this video on boat propeller action under water.

In a dysfunctional joint, the fluid within the joint space can be pushed away from one area of the joint causing high pressure on one side of the joint, and low pressure on the other. When manipulated, the two bones are pulled further away from one another.  As the joint space gets wider (up to 3 times its normal resting distance) the fluid under high pressure rushes towards to area of low pressure equalising it1. This process subsequently results in an increase in the joints range of motion, making it more mobile.

The researchers have put the videos from their experiment of cracking their knuckles in during and MRI showing the joint cavitation  click here.

Does Cracking Your Knuckles Cause Arthritis?

No.

Whilst there are some reported cases in the medical literature that assert that knuckle cracking is associated with an increased risk of arthritis of the hands and fingers2,3. These studies are now very old (from 1975 and 1990 respectively) and were not the most scientific of studies, even for their time. In fact, Castellanos (1990) in their study state that the vibration energy that result from joint cavitation “submits the joint to high impact forces” causing “joint erosion”. However, they failed to provide any evidence for this statement. They also conclude in the same study that: “There was no increased preponderance of arthritis in either hand group”. Meaning there was not increased rate of arthritis in the group who cracked their knuckles, compared to those who didn’t in their study.

There is evidence however, that shows that chronic, habitual knuckle cracking is associated with a lower prevalence of arthritis later in life1,2.

So, I am sorry to say to all those parents out there who tell their children “don’t crack your knuckles, you will get arthritis” that there is no evidence to support that statement. This is simply an old myth that needs to die away quietly into the night.

 

 

 

References:

  1. deWeber K, Olszewski M, Ortolano R. Knuckle Cracking and Hand Osteoarthritis. J Am Board Fam Med. 2011;24(2):169-174. doi:10.3122/jabfm.2011.02.100156
  2. Swezey RL, Swezey SE. The Consequences of Habitual Knuckle Cracking. Vol 122.; 1975. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1129752/pdf/westjmed00297-0049.pdf. Accessed March 20, 2019.
  3. Castellanos J, Axelrod D. Effect of habitual knuckle cracking on hand function. Ann Rheum Dis. 1990;49(5):308-309. http://www.ncbi.nlm.nih.gov/pubmed/2344210. Accessed March 20, 2019.

 

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