The reasons for the bending of the thumb joint include physiological reasons and pathological factors, physiological generally do not require treatment, pathological mostly caused by inflammation, it is recommended that timely medical treatment. 1, physiological factors: thumb bending at the existence of joint cavity, joint cavity is a closed cavity, filled with synovial fluid, the cavity pressure is less than atmospheric pressure, for negative pressure. Negative pressure and synovial fluid in the cavity can help the joint stability, when the joint is suddenly pulled or flexed, the negative pressure state will be broken, the surrounding gas will spread and emit a crisp popping sound. This is a physiological joint popping sound, crisp, single, non-repetitive, not accompanied by pain or discomfort, and often followed by a sense of relief. This is a normal physiological reflex, generally do not need treatment; 2, pathological factors: mainly for disease or joint structure variation and other factors, resulting in synovial roughness and joint capsule, ligament relaxation, tendons in the tendon sheath sliding friction can appear ringing, the situation is mostly seen in joint infection, stenosing tenosynovitis, osteoarthritis and other diseases. If a narrow tendon sheath develops in the thumb joint, a clicking sound will occur in the distal joint when the thumb joint is bent, and there will be obvious pressure points and swelling. Functional exercises should be performed under the guidance of a physician to relieve joint stiffness at a later stage.