When you move or bend your fingers, you occasionally squeeze tiny air bubbles that form in the protective fluid around your body’s joints. Those popping bubbles create an audible crack.
Like all joints, they’re the place where two bones come together to allow movement-we have them in our wrists, knees, and everywhere else we can bend. Tough, flexible tissues called ligaments hold them together. Joints are covered with a capsule filled with a special kind of liquid, called synovial fluid that acts as a lubricant as we move around; they also contain small amounts of dissolved gas, which is what causes that pop when we crack them.
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