To all you knuckle crackers ...

... you can sleep easier tonight. Knuckle cracking does not lead to arthritis. So why would I bother to blog about this today? For one simple reason. After a 50 year, single participant study, results have demonstrated that habitual knuckle cracking does not lead to arthritis. This research has advanced the field so much that it was given a 2009 Ig Nobel award. The original research (see citation below) was published in 1998. A link directly to the Letter to the Editor of the journal Arthritis and Rheumatism can be found here (PDF, 2 pages).

Donald Unger, an allergist in Thousand Oaks, California, earned the medicine prize for addressing another timeless question: does cracking knuckles really cause arthritis, as his mother warned him it would? As a child, he naturally thought his mother omniscient, but as a teenager he learned about science and started questioning received wisdom of this kind.

To resolve the issue Unger embarked on a long-term controlled experiment, and began cracking the knuckles on his left hand twice a day, but not those on his right (Arthritis and Rheumatism, vol 41, p 949). He has done so for more than 60 years, and never suffered arthritis in either hand. "Mother, you were wrong," he says, looking heavenwards. What he now wants to know is: "Was it really necessary for me to eat my broccoli?"

In the reported "study" the following was observed:

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.

Therefore, rest assured knuckle crackers (of whom I am one), your habit is not detrimental.

Reference
Unger DL (1998). Does knuckle cracking lead to arthritis of the fingers? Arthritis and rheumatism, 41 (5), 949-50 PMID: 9588755