Joints that crack may sound alarming, but it's almost always harmless, says a top spinal doctor.
"If it doesn't hurt you, you retain full freedom of movement and the joint isn't swollen in any way, there's no reason to worry about it," said Reinhard Schneiderhan, an orthopaedist and president of the German Spine League.
The quieter pops come from the synovial fluid in the joints as it is pressed into new locations during movement. Habitual knuckle-crackers appear to suffer no long term ill effects from this.
More abrupt cracks might be heard when a joint snaps into a new position. Ideally the new position will be benign, but we occasionally do pop out of joint, when the two parts of a joint mutually block, Schneiderhan said.