Most patients experience a popping or cracking sound during a manipulation, whether spinal or extremity. This is not dangerous, and it typically does not cause discomfort for patients. Contrary to popular belief, the sounds are NOT the bones cracking against each other, Instead, this sound occurs because gas and fluids are moving through the joint space. When pressure builds in a joint, you experience a lack of motion. The adjustment releases the pressure, causing a popping sound, similar to uncorking a champagne bottle.