Some parents unintentionally notice that the interphalangeal joint of their child’s thumb is flexed and cannot be straightened. When the thumb is broken with force, it can sometimes be straightened, often with a popping sensation. However, soon afterwards, the child’s thumb flexes again and returns to its old state. The scientific name for this condition is stenosing tenosynovitis, also known as “trigger finger”. The main manifestation is the flexion of the interphalangeal joint of the thumb, which cannot be straightened. There is no clear cause for this condition. Some scholars believe that it is congenital, while others believe that it is an acquired nodular enlargement secondary to flexor tendons. The age of onset ranges from being detected at birth to three years of age. The disease is usually diagnosed on the basis of the clinical presentation of the thumb, without the need for radiographs, etc. It has been reported that 30% of neonatal patients and about 12% of patients between 6 months and 3 years of age can heal spontaneously, and surgical treatment before 3 years of age has satisfactory results. In practice, early detection of this disease many parents will first try conservative treatment in the hope that their child will heal spontaneously. In most cases, after several weeks or months, the child’s thumb flexion never improves or gets progressively worse and some activities that require thumb flexion and extension are affected, then surgery is eventually required. Surgery is performed by making a small incision on the palmar aspect of the metacarpophalangeal joint, exposing the narrow tendon sheath and cutting it longitudinally to restore flexion and extension of the thumb. Since the cause of this disease is unknown, there is still a risk of recurrence after surgery. However, if the patient insists on passive exercise after surgery, avoids tendon sheath adhesions, and follows up regularly, there is little chance of recurrence.