Similarly, cracking knuckles was a mystery until Dr. Adrien Flatt (hand surgeon, U of Iowa) took scans of a knuckle being 'cracked'. It was bubbles in the joint

Similarly, cracking knuckles was a mystery until Dr. Adrien Flatt (hand surgeon, U of Iowa) took scans of a knuckle being 'cracked'. It was bubbles in the joint fluid being squeezed out of the compressed joint back into solution. Hey! I wonder if that action produces similar accelerations?