WHAT CAUSES THE CRACKING SOUND?

The cracking sound is gas being released from the joint. Gas is produced within the joint cavity but is constantly dissipated by normal joint movement.

 

If a joint becomes restricted in its range of movement or in some cases totally jammed, the gas is not released and gas builds up within the joint cavity causing the joint capsule to swell, irritating sensory receptors associated with the joint capsule causing it to be tender to palpate.

 

Once the gas has been released following manipulation the joint capsule will immediately feel far less tender to touch due to the release of the built up pressure within the joint capsule.