Why does breaking our bones hurt, but popping our knuckles, back, etc. feel good?

Answer 1

The answer lies with nerves. Bones do not have nerves, but have a white covering around the bone called periosteum, Within the periosteum are nocireceptive neurons. When bones break, these neurons send messages to the brain, which interprets the messages as pain. However, when you pop bones, these nocireceptive signals are not activated. Instead, the popping sound is, based on majority opinion in the scientific community, due to nitrogen gas bubbles being squeezed together in the space of the joint.