People are often curious about that “popping sound” they hear when getting adjustments.  Synovial joints (back, knees, fingers) are a type of joint that is surrounded by a capsule and filled with fluid. When you rapidly expand the space in the joint by doing an adjustment, the fluid turns to gas to fill the space.  These gas bubbles forming then dissolving are the sounds that you hear.  These cavitations are totally harmless and completely  normal. There is nothing being torn or broken.  Cavitations are not completely necessary for an adjustment to be effective.  You can still improve movement, neurological  function, and muscle tone without a cavitation, but they are a sign that things are moving well.  It is like a bonus to your paycheck, it is great to have it but you can still get the job done without it.  In fact, many times it is not as common to get cavitations with animals as it is with people. The goal of any adjustment is to open up the joint and thereby improve motion, joint health and nervous system input.