Thumping when bending the thumb needs a clear cause, some patients can be self-healing, if accompanied by other uncomfortable symptoms, it is recommended to consult a doctor in time. Causes of thumb thumping when bending include physiological factors, but also stenosing tenosynovitis, arthritis of the fingers, bone fracture and other factors. 1. Physiological factors: Normal friction of the joints can also cause rattling, and patients are usually not accompanied by other clinical symptoms, so there is no need for treatment, which is a normal physiological phenomenon. 2. Stenosing tenosynovitis: long-term hand workers can cause aseptic inflammation of the thumb. Mild tenosynovitis can be cured by sufficient rest, but stenosing tenosynovitis usually cannot be cured by itself, and needs to be treated under the guidance of a doctor. 3. Finger arthritis: arthritis of the thumb can also produce rattling sound when bending, finger arthritis is mostly related to trauma, chronic strain, infectious factors, immune diseases, finger arthritis can not be cured by itself, and need early diagnosis and early treatment. 4. Fracture: Fracture of the thumb can also produce a loud sound, usually minor fracture without displacement has the possibility of self-healing, but most of the fracture need to be braked and reset, or even surgical treatment in order to recover. If the thumb thumps when bending and is accompanied by other uncomfortable symptoms such as pain, it is recommended to go to the hospital in time to find out the cause of the disease, and be treated by the doctor, so as to avoid delaying the treatment and affecting the function of the thumb.