Há estudos para tudo e este estabelece que fazer estalar os nós dos dedos não faz mal (no curto prazo):
http://www.mirror.co.uk/science/cracking-your-knuckles-can-actually-8682115
Citando:
"Now we know cracking knuckles could be GOOD for you, let's see what actually happens when you do it [video in th link above].
The myth that cracking your knuckles is bad for you can be finally put to bed, after a study involving 40 volunteers showed that no short term damage was caused by clicking your fingers.
Researchers from the Radiological Society of North America, used ultrasound to analyse knuckle-cracking in real time. Using the imaging they were able to see exactly what was going on inside the joint at the exact moment of the "pop"."
