The possible causes of thumb shaking when it is flexed include soft tissue injury, bunion flexor injury, carpal tunnel syndrome, and so on. 1. Soft tissue injury: Sprains and contusions caused by direct or indirect external forces may result in damage to the muscles, ligaments, tendons and other soft tissues of the thumb, which may lead to shivering when the thumb is flexed due to poor recovery or prolonged strain. 2. Bunion flexor injury: When the muscle belly of the bunion flexor is injured, the muscle may become congested, swollen and dysfunctional, etc. The phenomenon may occur due to muscle spasms caused by frequent activities or overwork of the thumb. 3. Carpal Tunnel Syndrome: Programmers, chefs, etc., often use their hands so that the pressure of the carpal tunnel keeps changing, and the phenomenon may also occur when the median nerve is severely compressed by long-term strain. Thumb shivering when bending may also have other reasons, it is recommended to go to the regular hospital in time, improve the relevant examination, clear cause, under the guidance of the doctor to give targeted treatment or treatment.