Paul wrote:I tend to listen to the first hand experience of old ladies and men in the nursing homes I have fed because their fingers were so swollen they couldn't move them.
First hand experience is not valid evidence, sorry. There's a reason we don't just say "Well, a bunch of people say this, so that makes it true." There are thousands of people who swear up and down that tapping the lid of a soda can that's been shaken will make it not fizz up. This has been proven to be absolutely 100% false by experimentation, but people will STILL say it works.
This is much the same. I don't doubt the people in nursing homes have swollen fingers. I don't doubt that maybe they cracked their knuckles a lot. However, that doesn't mean that cracking their knuckles caused swollen fingers.
In many scientific fields, there is a statement that is repeated over and over. Namely, "Correlation does not imply causation." In other words, just because A happens, then B happens, does not mean A caused B. Even if every single person in the nursing home cracked their knuckles, and all had swollen fingers, that does not mean that cracking their knuckles caused swollen fingers.
You might say "But if everyone who did it had the same problem, doesn't that prove it?" Well, no. For a good example, here's this:
A. A rooster crows.
B. The sun rises.
Did the rooster crowing cause the sun to rise? No, that's absurd. But every day the rooster crows, and the sun rises. If the rooster didn't crow, the sun would still rise.
The study you quoted. The study is, of course, a correlational study. Causational studies cannot be done on this sort of thing for ethics reasons. It is unethical (and probably illegal) to perform studies that would theoretically cause harm to the participants. In this case, they said that those who cracked their knuckles frequently showed signs of hand swelling. That's nice, but here's the question: are those who crack knuckles more likely to have swollen hands, or are people who are already going to get swollen hands more likely to crack their knuckles for whatever reason?
See what I mean? It's also likely these people would have gotten swollen hands anyway, and that the knuckle cracking is merely a symptom.
Anyway that's about all I have to say on the subject. *shrug* I am not a doctor, and shooraijin is. So listen to him, not me. XD