Is Cracking Your Knuckles Bad for You?

Is Cracking Your Knuckles Bad For You

            *Crack* *Crack* *Crack crack crack*

            Behind you in the movie theater. Next to you in class. Across from you at the table at dinner. It is unavoidable. We are surrounded by knuckle-crackers. 25% of all Americans crack their knuckles (1). That means that in a room of four people, at least one has terrorized masses with their bodily function. However, even though knuckle cracking is common, many have theories that cracking your knuckles may be harmful and can even cause arthritis. However, studies have proven that there is no connection between knuckle cracking and arthritis, and that is nothing more than a low-risk habit.

            We have heard it all when it comes to knuckle cracking. Opinions vary greatly, and it is hard to decipher fact from fiction. A recent “WikiAnswers”* question was posted, and many responses were sent in. The responses are anonymous and posted on an online forum, and therefore cannot be valued as reliable sources. However, they do help to illustrate the variety of opinions which exists in reference to this question. Some argue that knuckle-cracking is harmful or alters your fingers.:                                                 

“Cracking your knuckles wears away the cartilage between the joints over a long period of time. This is one of the causes of arthritis.”                                                            “It only elongates the joints over time and gives you the appearance of longer fingers.”                                                                               “Knuckles can grow to be a bit larger than normal, but it's not noticeable.”                             “Finger and thumb arthritis is common, because there are 27 bones in each hand! This means that there are many joints in the fingers that can develop arthritis.”

We most often hear these sorts of responses from frusterated mothers trying to encourage their children to not crack their knuckles (mostly for the peace of mind of the mothers themselves). Others believe that knuckle-cracking can be beneficial.

“Cracking your knuckles actually has some benefits -- you'll feel looser and enjoy more mobility in your joints immediately after popping.”                                                          “If anything, it increases flexibility and keeps your fingers supple.”

But most just think that cracking your knuckles is neither harm nor beneficial.

“The cracking of knuckles is nothing compared to the every day abuse the joints go through in every day normal use”                                                                                “There has never been a meaningful study done that has shown knuckle cracking to be harmful to the finger joints.”                                                                                               “It is an old wife's tale that has been debunked many times.”                                        “Not harmful at all. It is perfectly fine. Don't do your neck though: let the chiropractors do that.”

However, the most interesting perspective came from someone who changes the perspective:

“Maybe it could be the other way around, maybe having arthritis even in the early stages makes some people need to crack their joints. Maybe it is a condition where some people have excess nitrogen build up in there joints making them feel uncomfortable and causing pain and related some how to having arthritis.”

This post is particularly interesting because instead of suggesting that whether it is good or bad, he or she suggested that perhaps knuckle cracking is not the problem; perhaps it is the effect not the cause.

            So what is the truth? The question of the reality of knuckle-cracking is so interesting because it is such a common act. “Knuckles” is simply the name we give to joints in our hands, which, like all joints in our body, hold together to bones and enable movement (2). Flexible tissue called ligament hold the bones together at the joints, and then the joints are covered with a capsule which holds a liquid called synovial fluid, which acts as a lubricant and has nutrients for the cartilage and bone (2). When one actually cracks his or her knuckle, she or he creates “negative pressure” (2) within the synovial fluid and it becomes a vacuum which then “allows more dissolved gas to enter the capsule as a bubble” (2). Once we manipulate the joint in a certain way, we hear a *crack* and the “bubble” bursts; the joint then refills with gas, which causes a delay time between when we can next crack. So the question still remains: to crack or not to crack?

            Throughout the years there have been many studies conducted to explore the answer to this question. Because there can be no actual connection established between knuckle-cracking and arthritis without there existing speculation, most studies try to find a pattern of causation. In 1998 Daniel Unger wrote a personal report in Arthritis and Rheumatism Magazine in which he detailed the account of his 50 year habit. For all 50 years he regularly cracked his left hand and not his right. After having both hands medically examined it was shown that he “had no excess of arthritis in his left hand compared with his right” (3). This particular account, although a personal study, is a good controlled experiment which helps to point to the probability that knuckle-cracking does not lead to arthritis.

            Further studies, perhaps more reliable than Unger’s study, due to the higher amount of trials and subjects, were conducted. In a paper entitled “Effect of habitual knuckle cracking on hand function” (4) by Jorge Castellanos and David Axelrod, a study is described with 300 participants. Castellanos and Axelrod explain that “the mechanicalsequelae of knuckle cracking have been shown to produce therapid release of energy in the form of sudden vibratory energy,much like the forces responsible for the destruction of hydraulicblades and ship propellers” (4). So Castellanos and Axelrod took this strong force and decided to further explore the effects it can have on knuckles. The 300 studied were all over 45 years old, and 74 were knuckle-crackers, 226 were not; within each groups the sex and age distribution was similar. The results were that there was “no increasedpreponderance of arthritis of the hand in either group; however,habitual knuckle crackers were more likely to have hand swellingand lower grip strength”(4). In other words, cracking your knuckles does not lead to arthritis, but can cause a weaker grip.

            There is more evidence to suggest this point, and many have written on it in scientific journals. Although the Castellanos and Axelrod study provided evidence for lower grip strength, it is not the only negative effect on the joints. A scientific journalist writes that “although cracking your joints will not lead to arthritis, overzealous cracking can injure the ligaments that support those joints” (2). So still there is still room for even more harmful effects to occur. The problem is well explained: “Measurements suggest that the energy unleashed when this happens is only about 7% of the amount you would need to damage cartilage” (3). This helps to explain that knuckle-cracking causing arthritis is very unlikely, but that there is a definite percent of cracking which causes harm. This 7% as shown above seems to create some but no major problems.

            The next question, then, is if arthritis cannot be cause by knuckle-cracking, is knuckle cracking a cause of arthritis? Can this question be taken a step further, perhaps to if knuckle cracking can prevent arthritis? A thorough scientific article on arthritis shows that knuckle cracking does not prevent or alleviate arthritis at all, but instead “can worsen the pain and inflammation" (5). It is true that people with arthritis have cracking sounds, but the two, voluntary and involuntary cracks, are not connected (6). Another article written by Pete Bonafede, MD, shows that knuckle cracking is just a tendency which we have due to everyday wear on our joints, and is no indication or prevention of arthritis (7).

            So will all the commotion of our cracks and resulting moans and complaints, knuckle cracking is “neither harmless nor desirable” (7). Therefore it is not recommended because it can cause a small amount of damage, but is not an extreme habit which should be avoided. There in fact exists no real connection, positive or otherwise, between arthritis and knuckle cracking. So perhaps we cannot silence the “crackers” in the theater, library, dinner table, or classroom, but at least we can silence the conversation and report proudly that knuckle cracking is a personal decision with few risks involved. Now comes the real question: should we tell the kids, or just let mothers keep lying to them?

 

 

 

 

 

(1) http://wiki.answers.com/Q/Does_cracking_your_knuckles_lead_to_arthr\

(2)http://www.washingtonpost.com/wp-dyn/content/article/2009/02/22/AR2009022201783.html

(3)http://www.thenakedscientists.com/forum/index.php?topic=17572.0;prev_next=next

(4)http://ard.bmj.com/cgi/content/abstract/49/5/308

(5)http://nz.answers.yahoo.com/question/index?qid=20070815155943AAbAeWZ

(6)http://www.webmd.com/osteoarthritis/guide/arthritis-basics

(7)http://www.providence.org/Oregon/Health_Resource_Centers/Arthritis/AskAnExpert_Arthritis_knuckles.htm