For many years now, there has been a claim that cracking your knuckles leads to arthritis in the future. Although this is a common belief, I still question if it is actually true. I’ve cracked my knuckles for years, despite my mom constantly telling me not to. My mom even went as far as to tell my doctor to tell me to not crack my knuckles. To my surprise though, my doctor said that cracking your knuckles has no correlation with arthritis. Although that made me happy to know, it made me question why such a common idea that arthritis can be caused by knuckle cracking was so easily rebuked by my doctor.
First of all, let me explain why people crack their knuckles and what they are actually doing when they crack them. Amanda Montell, author of the article The Real Reason You’re Addicted to Cracking your Knuckles explains that cracking your knuckles is basically a way to relieve pressure. After sitting in a position for a while, you want to stretch, and this is just a way some people do it. It’s similar to stretching your entire body, but instead it’s your joints. It gives the person a nice feeling, making it habitual and sometimes addictive (Montell 2016). That nice feeling is felt when the person stretches their bones apart, popping the bubble of fluid that builds up between the bones according to Harvard Health Publications’ article called Does knuckle cracking cause arthritis?
If cracking your knuckles is a pressure reliever than why do people associate it with such a bad thing like arthritis? That made me wonder whether if the correlation with arthritis is actually causal or not. There are four possibilities:
- Cracking knuckles directly causes arthritis.
- Arthritis causes one to crack their knuckles (reverse causation).
- There is a third variable that causes both arthritis and the cracking of the knuckles. For example, having a family history of arthritis might cause your arthritis and also stress you out, causing you to crack your knuckles.)
- The correlation between knuckle cracking and arthritis is due to chance alone.
According to Steve Mirsky, author of Crack Research: Good news about knuckle cracking, Donald Unger published a study in 1998 to see if knuckle cracking really causes arthritis. He cracked his left knuckles in his hand twice a day for fifty years. He used the right hand as the control. After all those years, he found that both of his hands were fine, despite the difference in knuckle cracking. This study that he conducted earned him an Ig Nobel Prize (Mirsky 2009.) This study ruled out the direct and reverse correlation between knuckle cracking and arthritis. He established that there is no correlation between the two. Here, Unger failed to reject the null hypothesis, that nothing was going on. Similar to smoking, a person might not smoke but still get lung cancer. Having it only being tested on one person can make the results ultimately due to chance alone. Still though, it is possible that a third variable could cause arthritis and knuckle cracking in another person. Although Unger’s study was long, it was only experimented on one person, himself. If he had conducted it on more than one person, he may have had different results. That being said, although this was experimental, it wasn’t large enough to 100% conclude anything.
Donald Unger
That being said, after researching more into this topic, I found a study conducted in 1990 by Jorge Castellanos and David Axelrod. In the study, they gathered 300 people 45 years old or older. They took into consideration third variables like evidence of possible muscular diseases, making sure no participants had them. Of the 300 tested, 226 did not crack their knuckles habitually and the other 74 were knuckle crackers. They took into consideration sex, smoking history, strength and other factors. After taking in all the factors, they concluded that there wasn’t a greater chance of arthritis in the habitual knuckle crackers over the non-knuckle crackers. They did do a further study that found habitual knuckle crackers had greater hand swelling, less strength, did more laborious things, were more likely to be smokers and drink alcohol. They did find that more non-knuckle crackers bite their nails (Castellanos, Azelrod 1990). The fact that non-knuckle crackers were found to bite their nails more may indicate that biting their nails is a way to relieve stress in imposition to relieving stress by cracking their knuckles. This study was observational because they didn’t ask certain people to crack their knuckles, but instead they just observed the effects.
Since the studies above are either observational or experimental but lacking enough evidence, I would want to conduct my own study. The study would be experimental, allowing me to manipulate the x variable. In the experiment, I would randomly select 1,000 students from Penn State. Each of the students would be asked the question, “Do you habitually crack your knuckles?” Based on that question, I would allocate the students into two groups. I would record the students age, history of arthritis, gender and muscular strength. I would then have them crack their knuckles every day for the next seven months. After the seven months, I would record the students hand strength again and also see if there are any possible signs of arthritis. I have to take into consideration though that not all the students may follow the instructions completely. Also I must keep in mind that signs of arthritis will probably not show up, that’s why I will make sure to look for decreasing muscular strength and any swelling that may appear in addition. Although this study is not perfect, you must keep in mind that the correlation between knuckle cracking and arthritis is like cancer and smoking. You won’t see any of the effects right away. That being said, it’s extremely hard to conduct an experiment over many years with many participants. You can’t trust that all the participants will follow the experiment’s rules or even stay in the experimental study for its entirety.
From these studies, I can conclude that knuckle cracking does not directly cause arthritis. Although reverse causation is unlikely, it is still a possibility. There isn’t enough information conducted to conclude that reverse causation is not possible. Both arthritis and knuckle cracking also may be both caused by a third variable like family history that indicates arthritis. Although this has been concluded, I still think that if one can, stopping or decreasing knuckle cracking is a good idea. Although knuckle cracking does not cause arthritis directly, it does cause other things. In an article by Mr. Mercola called Is Cracking Your Knuckles Harmful? he mentions the 1990 study mentioned above. He further explains that knuckle cracking can lead to swelling in the hands and essentially a decrease in grip strength (Mercola 2014). If possible, I think it’s best that one chances their habits to avoid hand issues in the future.
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Source 5 (make sure to click the PDF on the right side to view)
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Cracking my knuckles is a major bad habit of mine. I never knew that Arthritis could be passed down from generation. I like how you took components of the class lessons and included it in your blog. I live how you had four outcomes to your scenario.
When I saw the title for this blog I knew it was for me because I am constantly cracking my knuckles, with the thought in the back of my head that maybe I am doing my fingers a disservice. It wasn’t so much that my mom was harassing me to stop, more the fact of I have seen from personal experiences that doing it might not be the best idea. It wasn’t until my grandfather saw me doing one time, and felt that he had the knee to say something. He told me that when he was a child, he would constantly crack his fingers, it was his bad habit. As he got older through his life, he realized that he was getting small pains throughout his fingers, and it was relatively young also. Although his doctor really couldn’t point any fingers towards the cracking to have a direct impact, it might have been the reason because of it. Ever since my grandfather told me that story I have stopped because I don’t want to run the risk, even if there isn’t a direct correlation between the two.
Here is an article from Harvard Health that talks about how it might not necessarily cause arthritis but is certainly a good reason to stop:
http://www.health.harvard.edu/pain/does-knuckle-cracking-cause-arthritis
I thought it was effective how you started off your blog post with an anecdote. At first I was a little worried where the blog was going due to this. However, in the next paragraphs you went on to further enhance your entry with evidence and different conducted studies. The study done by Don Unger isn’t very reliable in my opinion. Since he did only conduct the study on himself, I believe it is more of an anecdote. We all know how reliable anecdotes are. They can be a sign of something, but they can be a coincidence or to to something else as well. However, your other studies included in your blog contribute to your hypothesis more effectively. I used to crack my knuckles in grade school. Then I stopped that and went through a phase of biting my nails. Eventually that ceased as well, and the cracking of my knuckles took its place. Till this day, I still crack my knuckles. Although, I only crack certain fingers…not all of them. I crack my pinky on my right hand, and both middle and ring fingers. I wonder why this is. I came across an article about the good and bad of cracking your knuckles. It talks about the difference between finger crackers and finger pullers. There is a difference between the two. It is quite interesting. The link below will direct you to this article.
http://www.techtimes.com/articles/46593/20150416/love-cracking-your-knuckles-heres-the-good-and-bad-about-it.htm
For me personally I don’t tend to crack my knuckles a lot but I do and thats exactly why I do it, to relieve pressure. If I’m sitting and rewriting my notes for class and my hand is hurting I will shake it out and crack both knuckles and the pressure is gone. I wonder if cracking your knuckle’s and pressure relieves the cramping sensation I feel in my hand sometimes. For me, I have also heard the correlation to hand cracking and Arthritis so I am glad it’s not true. I like how you incorporated a lot of science and scientific terms that are talked about it class. There was an interesting article that I found that you could read more up on about knuckle cracking and relieving the cramping sensation. Does the cramping ever happen to you? Why do you crack your knuckles?
http://www.livestrong.com/article/510583-how-to-relieve-cramping-fingers/
(Talks about relieving cramping and ways to do so and number 4 talks about knuckle cracking to relieve pressure)
As an avid knuckle cracker, I was drawn to this blog. Ever since I was little I have been doing it, and cannot seem to stop. My mom would always tell me to stop because she said it would cause arthritis and make your knuckles bigger. After reading this blog, I am glad that this is just a myth and don’t necessarily need to worry about getting arthritis. Other than cracking my knuckles, I often crack my neck and spine. Now this cant cause arthritis, but It is heard to cause some other major problems. Here is a link to a great article explaining the effects of cracking your neck and back your self. http://www.safebee.com/health/truth-about-cracking-your-neck
As an crazy knuckle cracker myself, it is second nature for me to constantly crack my knuckles. Your article clearly explained the issues this action could cause, and had me really thinking if I should or shouldn’t do it. Kind of comparing it to if cracking your jaw is bad, I don’t think any sort of forced body action is good. A question I am left wondering is if cracking our body parts is part of our natural human DNA or if it is a social habit that we all just started doing. Basically, is it learned or is it natural? Looking into it, not a lot of data was gathered on this information. I think the number one thing to pay attention when it comes to cracking parts of your body is how much you do it and how much you rely on doing it. My sister constantly claims she has to crack her hip or she can not sit down. The sound is so loud and disturbing. In cases like this, I don’t think she should continue doing this. If you are concerned about the sounds, here is a link to an article explaining the different feelings and sounds and what you should do about it. https://experiencelife.com/article/creak-crackle-pop/