Tenosynovitis in nine-month-olds is mostly pediatric stenosing tenosynovitis, which can be immobilized with splints for the purpose of adequate rest, and can also be treated with surgery for incision and decompression. Tendinitis in young children is mostly pediatric stenosing tenosynovitis, also known as trigger finger. Mainly due to the flexor tendon in the metacarpophalangeal joint area by the narrow tendon sheath binding, so that the proximal tendon edema thickening or nodular, so that the thumb is in a flexed position, can not be active straightening, passive extension can cause pain or popping, for congenital disease, mostly in 6 months ~ 2 years of age at about the time of the emergence of symptoms. Nine-month-old babies do not yet have a clear sense of individuality, and can be treated with localized hot compresses or local immobilization with splints to keep the tendon relaxed and well rested. When conservative treatment is not effective, it can be treated by tenotomy and decompression. Medications such as ibuprofen can also be used to relieve pain. Due to the young age of the baby, a doctor should be consulted for treatment. Please follow your doctor’s instructions for medication.