How is sound caused by cracking of knuckles?
Sound is caused by cracking of knuckles when a bubble which has formed in lubricating fluid (synovial fluid) which surrounds the two bones burst. The fluid prevents the bones from grating against each other and contains tiny bubbles that cannot be seen by nacked eye. So when the knuckle bones remain together the fluid is under pressure and bubbles remain tiny.But when one clenches their fist,the bones are pulled apart which cause the tiny bubbles form a larger bubble. These get burst when clenched and produce cracking noise. Docters are not sure whether cracking knuckles is harmful or not.
