What Exactly is Happening When my Joints Crack?

Whenever a joint makes a cracking noise its just the noise it makes when gases escape the joints. Our joints are surrounded by very smooth cartilage, which is protected by a liquid capsule type membrane. This fluid like substance is made up of carbon dioxide, oxygen and nitrogen. When the joints crack it releases gas bubbles. The release of these gases causes the cracking or popping sound that we can here and also feel.