Pain in the palm of the left thumb can be caused by the following reasons: first, tenosynovitis, when the thumb has stenosing tenosynovitis, there can be pain in the palm of the thumb, often in the metacarpophalangeal joint, there can be morning stiffness and popping, and in severe cases, there can be activity disorders, then we should go to the specialist for early examination, early closure treatment and surgery. Second, gout, gout can also involve the thumb, resulting in pain in the palm of the hand under the thumb, which can be accompanied by gout stone formation, then early blood uric acid tests and x-rays of the hand should be taken for early diagnosis. Third, osteoarthritis, often caused by degeneration or strain in the elderly, can cause pain in the palm of the hand under the thumb, which requires early X-ray examination of the hand for early diagnosis and treatment.