For some, knuckle cracking is reminiscent of Bollywood film heroes getting ready to take on 10 bad guys at once, while others just go about killing their idle time, turning and twisting their fingers and knuckles to produce a cracking sound. But why do we do it?

Knuckle cracking is a common habit among many, especially noticeable while taking a break from hours of work or while sitting idle at home. It is also a sign of nervousness or to deal with stress among some people, while for others it is merely something they do to pass the time.

There have been various arguments made for and against the practice (or habit) of knuckle cracking. Knuckle cracking has often been thought to cause arthritis—popping sounds made by other joints in the body are also linked to this chronic disease which causes joint inflammation. Although there isn’t conclusive evidence regarding this, it may be an underlying symptom if your knuckles or fingers hurt while doing so.

The "popping" sound that comes cracking ones knuckles is due to the extension of the joints in the fingers. There are theories that this causes the bubbles in the fluid of the joint to burst. This is why you cannot experience the same sensation immediately after cracking a finger, as the bubbles take some time to collect again.

Even though it is considered to be a largely harmless act, there have been instances of finger dislocations or flared or injured tendons as a result of cracking your knuckles too often. Read on for more on why we crack our knuckles and is it safe.

  1. Why do people crack their knuckles?
  2. Causes of knuckle cracking
  3. Side effects of knuckle cracking
  4. When should one see a doctor
  5. How to stop knuckle cracking

More than half the global population is estimated to have the habit of cracking their knuckles, which is significant, with more men indulging in this activity than women. And while most consider it to be a stress-relieving act, others around the person doing it may find it rude or impolite.

Many people find knuckle cracking to be second nature, close to other behavioural habits such as touching your face frequently. However, there are several reasons attributed to this practice and why people do it:

  • For most people, knuckle cracking comes from habit. Most habitual people end up cracking their knuckles at least five times a day, without even realising it.
  • Some people indulge in the habit simply because of the "popping" sound it makes, even while cracking their toes.
  • Knuckle cracking has also been associated with stress and as part of a person's coping mechanism to deal with it.
  • Feeling nervous or jittery about something can also produce certain physical reactions, and knuckle cracking is one of them.
  • The knuckle-cracking sound is thought to be a result of the bubbles in the fluid between joints bursting or popping, and some associate it with a tension relieving practice.
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Much like other joints in the body like the neck or the back, even our fingers and knuckles produce cracking sounds upon being bent or pulled a certain way. 

The popping sound is thought to come from the bursting of bubbles present in the fluid in the joints. These bubbles comprise gases such as carbon dioxide, which are released when the fingers are bent or extended from the joints.

However, studies done later on this subject suggest the sound hasn't been conclusively linked to the bursting of bubbles—instead, knuckle cracking leads to the formation of cavities. The scientists studied real-time footage using MRI images, and found that there was cavity creation in the joint when the joints were bent that resulted in the cracking sound.

Another study performed in 2018 found that the sound is caused by the partial collapse of the cavities in the joints, and it takes time for new cavities to be formed, which is the reason why you are unable to produce the same cracking sound immediately after cracking your knuckles once.

In an article published in the Swiss Medical Journal in 2017, titled "A review about sounds produced by joints", researchers said they found no evidence connecting cracking knuckles with arthritis. 

Another doctor performed a study on himself, having cracked the knuckles only on his left hand for 50 years more than twice a day, and avoided doing so on the knuckles in his right hand. He reported no difference between the fingers in either hand, nor did they show any signs of arthritis.

Another, much larger study published in the Western Journal of Medicine studied a geriatric patient population with a history of knuckle cracking and found no correlation between the habit and arthritis or similar degenerative conditions.

There have also been some other conditions associated with knuckle cracking, such as the habit could reduce the strength of your grip or lead to swollen or larger joints in the fingers, but no conclusive evidence has been found regarding such theories as well.

However, even though all available evidence points towards the activity being largely harmless, if knuckle cracking leads to pain in your fingers or joints or causes swelling, it is best to avoid doing it repeatedly. Pain in the fingers or swollen joints could point towards an underlying condition such as gout, or even arthritis, even though there isn’t a direct correlation between the two.

Another danger of knuckle cracking too often or vigorously is that can lead to finger dislocations or tendon damage.

Although available research suggests that knuckle cracking is mostly a harmless habit, some of the above-mentioned instances could cause you to take a trip to the doctor's office:

  • If your fingers begin to swell, hurt or become crooked or bent in one direction, it is best to get it checked by a doctor.
  • If the knuckle cracking leads to pain or swelling, it may be because of an underlying condition—it is best to get it looked at by a medical professional in this case.
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Knuckle cracking may not be harmful as previously thought, but it can be a source of distraction or irritation to those around you. Here are some ways you can break this habit and avoid knuckle cracking altogether in the long run:

  • Keep your fingers and hands occupied by holding things like a stress ball, book or keep yourself engaged in an activity.
  • Look for other ways to manage your stress, with the help of meditation, breathing or physical exercises.
  • Be conscious about your habit and those around you, and make the effort to stop yourself from doing so each time you feel like it.
  • Try to understand the reason why you do it, make your friends or family members point it out when you do it to help you stop.


  1. Health Harvard Publishing: Harvard Medical School [Internet]. Harvard University, Cambridge. Massachusetts. USA; Knuckle cracking: Annoying and harmful, or just annoying?.
  2. Swezey RL et al. The Consequences of Habitual Knuckle Cracking The Western Journal of Medicine. 1975 May; 122: 377-379.
  3. Saubade M et al. A review about sounds produced by joints Rev Med Suisse. 2017 Jul 12;13(569):1334-1338.
  4. deWeber K et al. Knuckle Cracking and Hand Osteoarthritis Journal of the American Board of Family Medicine. 2011 Mar; 24 (2): 169-174.
  5. Kawchuk GN et al. Real-Time Visualization of Joint Cavitation PLoS ONE 10(4): e0119470.
  6. Suja VC and Barakat AI. A Mathematical Model for the Sounds Produced by Knuckle Cracking Scientific Reports. 2018 Mar; 8: 4600.
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