Does Jointcracking lead to arthritis?


  • Community Lead

    According to Reuters Health it does not.
    TODO: Unfortunately, at this time access to this post has been limited. When I can regain access to this article I shall repost the information in full here.

    Another interesting article on this topic has an accumulation of fellow Jointcracker opinions:
    http://www.faqfarm.com/Q/Does_cracking_your_knuckles_really_give_you_arthritis


  • Community Lead

    Ian A. York, Ph.D iayork@panix.com , a research fellow at the department of pathology of Harvard University posted a very interesting study about then current scientific papers on the above question to alt.folklore.urban on November 21 1995.

    He meanwhile posted
    his original write up on his homepage at

    I took the liberty to mark especially interesting passages in bold.

    The question is usually, "Will cracking my knuckles cause arthritis?" and there are probably two myths given as the answer. One is "yes", and the other is "no."

    Oddly enough, medical science has not devoted great attention to this vital question. A while ago I posted some abstracts about it; more recently I read some 83% of the world's literature on this subject (the sixth paper was torn out of its binding) and the answers are far from clear.

    Two papers ([4] and [5]) were essentially case reports, or were too small to be reliable. One [2] was a larger study, one [1] was a review with some original data, and the other one [3] was a letter commenting on [2]. The first two can be pretty much dismissed; [4] simply found a guy with arthritic hands who cracked his knuckles (and had no obvious predisposing signs for arthritis) and concluded the knuckle-cracking was causative; this is a meaningless correlation.

    [5] was slightly better; they surveyed elderly people for arthritis of the hands and then asked which of them were 'habitual knuckle-crackers'. However, the numbers were too small to give much information; I also have serious questions about their method of identifying knuckle-crackers. (They found that 11 of the 23 women they asked self-identified themselves as knuckle-crackers. Perhaps I've been leading a sheltered life, but this sounds awfully high to me. Does anyone out there find that half of the little old ladies they meet habitually crack their knuckles? Perhaps their subjects took the question to mean 'Have you ever cracked your knuckles?" instead.)

    Now we get to the interesting papers. [2] looked at a larger number of people (300 people, of whom 74 admitted to being habitual knuckle-crackers - a number that sounds closer to my expectations than the previous one) and studied a variety of hand functions. Most were normal; in particular, there was no increased incidence of arthritis. However, the KC group was more prone to swelling of the hand, and also had reduced grip strength.

    When I posted the abstract to this paper, someone on the group pointed out that the KC group were also found to be more likely to be manual labourers, and noted that they therefore might have been more prone to hand trauma, which (rather than the KC itself) could have led to the hand problems. This was a fair point that wasn't addressed by the abstract, although I assumed the study would have considered this rather obvious potential confounding factor; this is why I checked the full paper. The authors do indeed consider it, and conclude that it seems unlikely, since the KC group was no more prone to trauma or hand surgery, or to other hand problems.

    However, the followup letter [3] makes another point - which is that the correlation doesn't demonstrate cause. The writer suggests that, for example, people with unusually loose joints may be more prone both to crack their knuckles and to joint damage because of the loose joints. This is fair too - although pretty speculative - and so the question remains open.

    One thing we can safely conclude, though, is that KC does not cause arthritis. Even in the relatively large study, the KC group was not found to be more prone to arthritis. So technically, the "no" answer is correct. However, since I doubt that most people draw a sharp distinction between developing osteoarthritis of the metacarpophalangeal joints and chronic inflammatory damage to the ligamentous capsule of the metacarpophalangeal joint (both hurt) I don't think a "no" answer here really addresses the question.

    This brings us to the last study [1]. Here Brodeur considers some potential mechanisms by which KC could induce damage. They point out that the mechanism responsible for the noise - cavitation - is the same principle that causes damage to plane and ship propellers. However, a calculation of the energy released by a single crack puts it at 1/10 the level necessary to cause damage. If we accept this - and it seems reasonable - then the question becomes whether chronic low-level assault can cause damage in the long term. There's no evidence either way for this, and it's as easy to come up with rationales on both sides.

    There's another mechanism that Brodeur mentions more in passing, that I think is at least as plausible as cavitation. During the KC process, the ligaments around the joint are rapidly stretched. Could this lead to chronic damage? It seems to me that it certainly could. A similar effect strikes, for example, pitchers; the trauma involved in pitching a single game may not cause any particular damage, but as we all (where "we all" equals North American baseball fans) know pitchers' joints and ligaments are more prone to damage over the long term than are the average person's. The stress involved in cracking a knuckle may be less than that involved in throwing a baseball 97 miles per hour, but on the other hand (Ha!) the ligaments involved are less robust, and while a pitcher may deliver some 100-odd insults to the ligaments every five days, I imagine a confirmed knuckle cracker is well above that.

    So what can we conclude? There's weak evidence for some damage to the joints; there's a reasonable, but speculative, model for the mechanism. There is hard evidence that the effect is not inevitable; not all members of the KC groups showed damage. I would conclude, personally, that it's quite likely that cracking your knuckles could lead to some unpleasantness down the road; and since there's little reason to continue an annoying and asocial habit, I'd suggest quitting. But since your loved ones have probably already suggested this many a time, it's unlikely you'll take my word for it.

    If I were writing the FAQ, I'd say something like this:

    F: Cracking your knuckles causes arthritis.
    Tb/U: It may damage your hand in other ways.

    Here are selected bits of the references in question:

    [1] Brodeur R.
    The audible release associated with joint manipulation.
    Journal of Manipulative & Physiological Therapeutics. 18(3):155-64, 1995

    […]
    Damage Due to Habitual Joint Cracking
    There has been very little work done to determine the long-term effects of habitual joint cracking. The scant literature that is available on this topic indicates that habitual knuckle cracking may have a direct effect on the soft tissue of the hands and there is a case study that indicates it may also cause damage that leads to radiologic change (17). However, there is insufficient evidence to make any conclusive statement regarding the long-term effects of habitual knuckle cracking.
    [review of the Swezey and Swezey report: no significant difference.]
    [review of the Catellanos and Axelrod report.] The knuckle crackers had approximately 75% less grip strength and a higher incidence of hand swelling. Because the average duration of the knuckle cracking habit was 35 +/- 18 years, the habit seems to have little effect on joint cartilage. The increase in joint swelling and the decrease in hand function indicates that habitual knuckle cracking has a greater effect on the soft tissue than on the bone or cartilage. However, damage to the cartilage cannot be ruled out. Watson et al [review of Watson et al.]
    [ … ]
    Joint Damage from Habitual Joint Cracking
    [ … ]
    Watson et al estimated the energy released by the cracking sound to be 0.07 mJ/mm^3 (15). Cartilage requires impact energies on the order of 1.0 mJ/mm^3 to cause damage to the articular structure and chondrocyte death (26). The effect of a single joint crack is less than 10% of this value and the energy released would be released in terms of damage to cartilage. Watson et al. argue that the effects of habitual joint cracking may be additive: the energy released during cavitation may be, over a period of time, sufficient to damage the articular cartilage (5,17,23). Although Watson et al. proposed this theory as a cause of direct damage to the joint cartilage, there is little clinical evidence to support this mechanism. [ … other possible damage mechanisms ...]
    The evidence of tissue swelling with habitual joint cracking indicates that the only area of injury would be at the proposed snap-back interface between the capsular ligament and the synovial fluid. Microtrauma may occur at the portion of the ligament involved in the snap-back and excessive joint cracking may ultimately lead to swelling of the ligament. This mechanism is completely speculative, but at least it has the support of clinical evidence (19). [ … ]

    [2] Castellanos J. Axelrod D.
    Effect of habitual knuckle cracking on hand function.
    Annals of the Rheumatic Diseases. 49(5):308-9, 1990

    Discussion
    The development of arthritis of the hand as a result of habitual knuckle-cracking has been considered an old wives' tale. Swezey reviewed 28 nursing home patients who could recall whether or not they had cracked their knuckles. Among these patients, a relationship between knuckle cracking and arthritis could not be found[1]. Indeed, metacarpophalangeal osteophytes were found in patients who had not been habitual knuckle crackers.
    Yet a bioengineering study of cracking joints suggested the potential for significant joint damage.[2] When tension is applied to the joint, cavitation occurs within the synovial fluid. This creates an unstable condition as the pressure within the bubble is lower than that of the surrounding fluid. Because the joint separation occurs at a high rate the net flow of synovial fluid is toward the low pressure regions, with a collapse of the vapour phase of the cavity. There is a release of vibratory energy, which may be responsible for the cracking sound.
    It is this phenomenon which is responsible for the erosion of ship propellers and the blades of hydraulic turbines.[3]
    Given the potential damage caused by this cavitation phenomenon, one might expect habitual knuckle cracking to cause some decrement in hand function, if not accelerate the onset of osteoarthritis of the hand.
    Of the 300 patients studied, 74 admitted to habitual knuckle cracking for 35 ( 18 ) years. Their s* x distribution was similar to that of those denying knuckle cracking. Those patients who were habitual knuckle crackers were more likely to have swelling of the hand and lower grip strength (table 2). Other factors which might influence hand function, such as carpal tunnel syndrome, contractures, surgery or trauma to the hand, and the presence of Heberden's or Beouchard's nodes, were equally present in both patient groups. Habitual knuckle crackers however, were more likely to be manual labourers with higher incomes (tables 1 and 2).
    Although the cause of habitual knuckle cracking was not considered in this study, patients admitting to it were more likely to bite their nails, smoke, and drink alcohol, as were members of their families (table 2).
    This study suggests that although habitual knuckle cracking does not relate to osteoarthritis of the hand, it may relate to decreased hand function. Therefore, habitual knuckle cracking should be discouraged.

    [3] Simkin PA.
    Habitual knuckle cracking and hand function.
    Annals of the Rheumatic Diseases. 49(11):957, 1990

    SIR: In a recent survey Castellanos and Axelrod evaluated 300 consecutive outpatients at Mount Carmel Mercy Hospital to determine whether habitual knuckle cracking is a risk factor for hand dysfunction. They found no relation with osteoarthritis, but noted that 'knuckle crackers were more likely to have hand swelling and lower grip strength' and concluded that 'habitual knuckle cracking results in functional hand impairment. I believe they have not established cause and effect in these interesting correlations.
    Not everyone can crack their knuckles. Some do so with ease, whereas others are quite incapable of performing this feat. No one has determined how the joints of these groups differ. It is quite possible, for instance, that metacarpophalangeal joint laxity may both facilitate knuckle cracking and impair hand function. As this hypothesis implies that hand swelling and diminished grip occur secondary to articular structure rather than abuse, it may be that nervous citizens of Detroit can continue to crack their knuckles without fear of injury.
    'Will cracking my knuckles hurt my hands?' remains a common gambit when a rheumatologist is identified as such among new acquaintances striving to make conversation. I still believe that the answer to this question is no, but perhaps it is time that we really found out.

    [4] Watson P. Hamilton A. Mollan R.
    Habitual joint cracking and radiological damage.
    BMJ. 299(6715):1566, 1989

    A 25 year old Malaysian man who habitually elicited cracking sounds from many of his joints was investigated during a study of joint cracking. He had no symptoms or obvious abnormalities of his joints, but a radiograph of his right hand showed ligamentous ossification on the ulnar side of his third metacarpophalangeal joint and chondrocalcinosis in the first and fourth metacarpophalangeal joints (figure). There was no evidence of osteoarthritis.
    Distraction of the articular surfaces during finger pulling lowers the pressure of the articular fluid. When the vapour pressure is reached the fluid evaporates, giving a cracking sound and forming an intra-articular bubble. Previous studies have reached conflicting conclusions about the radiological changes found in habitual finger cracking,[1,2], but we suggest that excessive joint cracking caused the changes seen in this subject, who had no signs of any other underlying disease.

    [5] Swezey RL. Swezey SE.
    The consequences of habitual knuckle cracking.
    Western Journal of Medicine. 122(5):377-9, 1975

    [ … ] The patient population consisted of 28 persons, with an average age of 78.5 years, of whom 23 were women and 5 were men. […] [ from Table 2: 11 women and 4 men were habitual knuckle-crackers ]

    Conclusion
    The data fail to support evidence that knuckle cracking leads to degenerative changes in the metacarpal phalangeal joints in old age. The chief morbid consequences of knuckle cracking would appear to be its annoying effect on the observer.

    [6] Unsworth A. Dowson D. Wright V.
    'Cracking joints'. A bioengineering study of cavitation in the metacarpophalangeal joint.
    Annals of the Rheumatic Diseases. 30(4):348-58, 1971

    I will try to hunt for the referenced documents and put them into a pdf format to post here. Of course, I welcome every help in this undertaking.

    So far I have not found any web search allowing a download of similar documents.


  • Community Lead

    This post has many interesting details http://answers.google.com/answers/threadview?id=121033

    Unfortunately, I don't have time to dissect the article right now. I only noticed some links in this article came up dead.

    Maybe someone else can.


  • Community Lead

    We all know excessive knuckle cracking leads to reduced grip strength.

    This fact does also support the theory that Jointcracktitis is actually caused by Hypermobile Joints / Lax liagments.

    Lax liagements / lax muscles = weak grip strength.

    I'm glad I'm finally starting to see some logic in all this clouded mys(t)ery.



  • With the lax grip - now i know why it has happened to me - because of my cracking.

    Wow JC - you quote and write a lot using technical terms i have never heard of in my 14 years of life :lol:



  • @Blaze:

    With the lax grip - now i know why it has happened to me - because of my cracking.

    Wow JC - you quote and write a lot using technical terms i have never heard of in my 14 years of life :lol:

    he seems an experienced man :)



  • He actually isn't, just an ordinary cracker like anyone else if you have read through the forum.



  • ah i see


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