[every]

I knew an osteopath in Tulsa. I asked him about the popping thing and he gave me a straight answer (I think). He said you have a fluid sealed into your joints and like all fluids in your body, there are gases dissolved in it. If you distort the joint enough these gases will pop out of solution, like opening a can of soda or a bottle of champagne. This pop is quite forceful and stimulates nerve endings around the joint which produces (temporarily) localized muscle relaxation and a mild analgesic effect. That's why it feels better. And it takes time for the gases to be reabsorbed which is why you have to wait before you can pop the joint again. And yes, the rest is essentially bullshit...