There are three main reasons why the neck clicks: 1. Gas escapes. In our body between the joints, there is a liquid called synovial fluid, which is used to lubricate the joints, there are also some gases within this liquid, such as oxygen, nitrogen and carbon dioxide, these gases form bubbles in the synovial fluid, when stretching the joints, the gas in the synovial fluid runs away sharply, it causes the neck to click, because the bubble breaks. 2, joint displacement. When moving the joint, the tendon ligaments shift, and when the tendon ligaments return to their original position, a clicking sound is sometimes heard. 3. Arthritis causes rough joint contact surfaces. Arthritis can destroy the cartilage tissue between the joints, causing the joint contact surface is no longer smooth, in this case, the joint friction will emit a clicking sound.