Question
When you pop your back the noise comes from the joints and the ligaments. I was told that there is nitrogen in the back and when the back is popped this gas is let out and is a pain reliever. Is this true?

Answer
Cynda,

     Just like any hydrolic fluid, your joint fluid builds up gases (there is no blood supply to the joints).  When the joint is release there can be a "popping sound" which is gas releasing from the joint.
A adjustment from a doctor of Chiropractic restores the joint to it's normal position and reducing pressure on the surrounding nerves which does release natural endorphins etc.  

Have a great day,
Dr. Brendon O'Brien D.C.