Congenital stenosing tenosynovitis in children is a common condition in pediatric orthopedic clinics, manifesting as a flexion deformity of the interphalangeal joints, most of which do not heal spontaneously after more than 6 months. It occurs mostly in the thumb, followed by the middle and ring fingers. It is usually detected a few weeks or months after birth, but is often not taken seriously by the parents until the age of about 2 years or even older. There are various treatments for congenital stenosing tenosynovitis, such as early immobilization and braking, acupuncture, surgery, and local injections. Pediatric tenosynovitis can be treated safely and predictably with A1 slide release and resection. Previously, it was thought that local seal treatment had some side effects and inaccurate efficacy for children, especially pediatric patients. However, we have improved the cure rate by using a modified local injection method plus early functional exercises for several children since 2007. Etiology and pathology: When the tendon crosses the joint, it is bound by a tough tendon sheath on the periosteum, forming a “bone-fiber tunnel” to prevent the tendon from springing up like a bowstring or slipping to the sides. The proximal or distal edge of the tendon sheath is stiff, and the thickening of the tendon sheath is most evident at the metacarpophalangeal joint, called the annular ligament. The tendon sheath thickens the most at the metacarpophalangeal joint and is called the annular ligament. When the tendon rubs excessively on this edge for a long time, inflammation of the tendon and tendon sheath can occur. However, because the tendon sheath is tough and inelastic, as if the hyperplastic, edematous tendon sheath is stuck in the tendon, so it is called stenosing tenosynovitis. The cause of pediatric stenosing tenosynovitis differs from that of adults in that it is mostly due to congenital malformations, such as a thicker first metacarpal bone or congenital hypertrophy of the tendon sheath resulting in narrowing of the tendon sheath opening. The tendon sheath edema and hyperplasia narrow the “bone-fiber tunnel”, which in turn compresses the edematous tendon. The tendon sheath cavity is particularly narrow and tough in the annular ligament area at both ends of the tendon sheath, so the edematous tendon is compressed in the shape of a gourd, which hinders the sliding of the tendon, such as forceful extension and flexion of the finger, the gourd-like enlarged part is forced to squeeze through at the annular ligament, resulting in popping action and ringing. Repeated friction between the tendon and tendon sheath, the tendon and tendon sheath edema aggravated, forming a vicious circle, and eventually developed into interphalangeal joint interlocking in the flexion position. Previously, it was thought that conservative treatment of congenital stenosing tenosynovitis of the finger in children was usually ineffective and should be treated surgically. However, we were able to cure 26 patients with tenosynovitis by using local seal plus functional exercise, and there was no recurrence at 2-year follow-up. The aim of treatment is to eliminate the inflammatory reaction and hyperplasia, hypertrophy and adhesion of the tendon sheath, and to restore the normal shape of the tendon and tendon sheath. Trimethoprim is a long-acting glucocorticoid, which can reduce capillary permeability, eliminate edema, inhibit inflammation and connective tissue proliferation, and reduce tendon sheath and tendon hypertrophy and adhesions. Since the tendon sheath is a small cavity, the key to injection therapy is whether the drug can be injected into the tendon sheath accurately, and only 3ml of a mixture of lidocaine tretinoin and water for injection can be injected. Caution: The above injection therapy has some side effects on children, especially pediatric patients, and can cause finger necrosis if too much tretinoin mixture is injected. In children with small fingers, only 3 ml of lidocaine and tretinoin mixed with water for injection can be injected. The timing of functional exercise is after a week of tendon sheath relaxation, and the amount must be sufficient. It must reach the amount of 100-200 exercises per day and persist for more than half a month. The method of both local sealing and early functional exercise is an effective way to treat congenital stenosing tenosynovitis of the thumb in infants and children and to ensure normal development of the affected thumb. Congenital stenosing tenosynovitis in children can be treated safely and predictably with local sealing plus early functional exercises, and is suitable for universal implementation in hospitals at all levels.