Best to just present this in full:
During the author’s childhood, various renowned authorities (his mother, several aunts, and, later, his mother-in-law [personal communication]) informed him that cracking his knuckles would lead to arthritis of the fingers. To test the accuracy of this hypothesis, the following study was undertaken.
For 50 years, the author cracked the knuckles of his left hand at least twice a day, leaving those on the right as a control. Thus, the knuckles on the left were cracked at least 36,500 times, while those on the right cracked rarely and spontaneously.
At the end of the 50 years, the hands were compared for the presence of arthritis. There was no arthritis in either hand, and no apparent differences between the two hands. Knuckle cracking did not lead to arthritis after a 50-year controlled study by the one participant. While a larger group would be necessary to confirm this result, this preliminary investigation suggests a lack of correlation between knuckle cracking and the development of arthritis of the fingers.
A search of the literature revealed only one previous paper on this subject, and the authors came to the same conclusion (Swezey RL. Swezey SE. The consequences of habitual knuckle cracking. West J Med 1973;122:377-9.).
This result calls into question whether other parental beliefs, e.g., the importance of eating spinach, are also flawed. Further investigation is likely warranted.
In conclusion, there is no apparent relationship between knuckle cracking and the subsequent development of arthritis of the fingers.
This study was done entirely at the author’s expense, with no grants from any governmental or pharmaceutical source.
Donald L. Unger, MD
Thousand Oaks, CA