Parents often encounter children with difficulty in straightening their thumbs, most of whom are found unintentionally for a few days or up to a year, mostly between the ages of 2 and 5, with more girls than boys. The cause of this condition is not well understood, but pathological changes can be seen in the A1 carriage of the thumb, which becomes narrowed and the thickened tendon sheath of the long flexor thumb becomes hypertrophic and hyperplastic, forming a pyknotic nodule that prevents the tendon from passing through the carriage during extension and flexion activities, resulting in a flexed thumb. In this case, the surgeon will recommend surgery to cut through the narrow carriage and remove the hypertrophic tendon sheath, and the thumb will immediately be able to extend and flex freely, although it may take a little longer to recover in children with a long history. Physical therapy and local massage do not solve the problem and may sometimes increase adhesions between the tendon and the tendon sheath, which may affect the functional activity after surgery.