A commonly held belief is that cracking one' s knuckles causes arthritis. But this is, in fact, false, as indicated by the fact that most people with arthritis never cracked their knuckles. The reasoning is flawed because the argument ['concludes that knuckle-cracking does not cause arthritis by appealing to an applicable principle', 'treats the absence of a condition in some people afflicted with a disorder as evidence that the condition never causes the disorder', 'ignores the possibility that arthritis is caused by genetic factors', 'makes a distinction between people who crack their knuckles and people who do not when there is no actual difference between these two groups of people']