Some of you may have seen the article. When osteopaths manipulate your joints and they go pop or crack, the process has been confirmed. As the joint is pulled apart carbon dioxide dissolved in the synovial fluid aggregates and creates a bubble, the surface tension breaks, the bubble bursts and you hear a pop or click. You'll often hear us say, it can be effective without a click, because we are aiming to override and reset inappropriate muscle tension which is holding the joint in a restricted position, and the small sharp movement when the joint is held in tension can do that, cavitation or not. We can feel whether that has happened and you can usually feel that the joint is easier; however an accompanying crack or pop does seem to often accompany satisfactory results, so perhaps it adds to the process. The MRIs also showed a white flash which (it was reported) may be water being drawn to the joint and thought to be beneficial. My thoughts are that the breaking of the surface tension of a bubble of carbon dioxide is also likely to release heat inside the joint as well as sound, and perhaps this 'deep heat' helps allow the deep intrinsic muscles around the joint to release. Not necessary for a successful manoeuvre, but perhaps a useful 'nice to have'