Thumb tremor when bending can be associated with overworked fingers, stenosing tenosynovitis, and Parkinson’s disease. If you make a fist for a long time or operate a cell phone with your thumb for a long time, your finger muscles will be overworked, and you will experience a tremor when you bend your thumb, which is usually relieved after resting. In the case of stenosing tenosynovitis of the flexor tendon of the thumb, as the tenosynovitis restricts the movement of the flexor tendon of the thumb, the symptom of tremor of the finger when bending will occur. If the symptoms are mild, it can be treated with heat and massage, and if the symptoms are severe, it can be treated with surgical tenotomy. Older people with Parkinson’s disease may also experience symptoms of hand tremor when bending the thumb. There are many other causes of tremor when bending the thumb, if there is a tremor when bending the thumb, it is recommended that the patient go to the hospital for medical treatment, to clarify the cause of the disease and receive regular treatment.