The brake fluid analogy

So here's a thought.  In my last post I talked about the new research which had proven once and for all that the pop (cavitation) you sometimes hear when a joint is manipulated is carbon dioxide suspended in the synovial fluid (the joint lubricating fluid) forming a bubble which explodes under the negative pressure caused by pulling the joint surfaces apart quickly.  They also noticed what they thought may be water rushing into the joint after the event. So lets assume that the cavitation has enough force to drive the carbon dioxide through the capsule round the joint, which creates a pressure gradient whereby water is attracted in to equalise the pressure, so effectively carbon dioxide has been replaced with water.  One of the effects will be on the compressability of the the synovial fluid, gases are compressible and liquids aren't.  That is why a car with old brake fluid will have a spongy feel to the brake pedal, as much of the force applied is absorbed by the gas compressing.  Maybe, just maybe, this is one of the ways that manipulations help joints to function better, by effectively changing the brake fluid, so that joints are less compressed.

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