What is the reason why children's fingers, joints and wrists click? 12 year old male.

Many people like to fiddle with their knuckles. Don't think this is a very simple thing. In fact, no one's finger joints can ring twice in five minutes. Try it yourself if you don't believe me: prepare a watch, break a joint of your finger first, and start timing when you can't hear the noise. If you can ring the bell to the same place again in five minutes, you win. The noise of finger joints is caused by the bursting of air bubbles. There is a certain amount of liquid in human finger joints, and a small amount of gas is dissolved in the liquid. When the finger joint is stretched, the pressure on the liquid is reduced, and the gas originally dissolved in the liquid escapes from it (this phenomenon can also occur when the soda bottle cap is opened). But the bubbles in the knuckles can't go anywhere else. In about fifteen minutes, the bubble will be absorbed by the liquid in the finger joint again, so if you want to ring your finger again, you must wait patiently for fifteen minutes, which is impossible. The space between our joint capsules is filled with synovial fluid, which plays a role in lubricating the joints. Synovial fluid contains carbon dioxide. When the joint is pulled and squeezed, the connective tissue of the joint capsule will change the shape of the joint capsule due to external force. If the pressure of synovial fluid decreases due to the increase of capsule cavity, the solubility of carbon dioxide in synovial fluid will decrease due to the sudden pressure drop, and then it will escape from synovial fluid to form small bubbles. These small bubbles will not exist for a long time, because the low pressure in the synovial sac makes the small bubbles burst almost immediately, which makes the synovial fluid impact the space occupied by the small bubbles, thus causing the sound of joint coffee. In addition, snapping fingers will make them thicker, because there will be some cartilage and sponge in the middle of finger joints. Breaking your fingers for a long time will make these cartilage and sponges swell.