The noise when bending the thumb may be caused by physiological or pathological factors, such as stenosing tenosynovitis, osteoarthritis and so on. 1. Physiological factors: there is a joint cavity in the thumb flexion, which is a closed cavity filled with synovial fluid, and the pressure inside the cavity is negative. When the joint is suddenly pulled or flexed, the negative pressure state will be broken, and the surrounding gas will spread out and make a crisp sound. Usually there is only a single ringing sound, no pain or discomfort, this situation is a normal physiological reflex, generally do not need treatment. 2. Pathologic factors (1) Stenosing tenosynovitis: If there is hyperplasia in the tendon sheath it can get stuck in the tendon. When the finger joints are excessively flexed or extended, there will be a localized noise and obvious pain at the same time. (2) Osteoarthritis: Inflammatory stimulation leads to rough synovium and laxity of the joint capsule and ligaments. When the tendon slides in the tendon sheath, the friction can make a loud sound, and will be accompanied by joint pain. The joints of the fingers are usually stiff and uncomfortable after getting up in the morning. When there is a ringing sound when bending the thumb, if it is accompanied by pain, redness and swelling and other discomforts, it is recommended to consult a doctor in time, follow the doctor’s instructions for further examination, and carry out targeted treatment or therapy with the help of the doctor.