Infant’s thumb may not be straight, which is a normal phenomenon and needs to be closely observed, or it may be related to tenosynovitis of the fingers, which needs to be treated with medication and surgery. Low-age infants, such as newborns who are not yet a month old, the thumb can be bent and not straight, mainly because the fetus in the mother’s body is in a state of curled up, with the continuous growth and development of the thumb can be recovered on their own, parents should be closely observed for a long time not to recover which should be promptly consulted for medical checkups. Typical symptoms of finger tenosynovitis are unfavorable finger flexion and extension, and limited activities. Common treatment drugs include ibuprofen, prednisone acetate, etc., which are mainly used to relieve inflammatory reaction and reduce pain. Surgical procedures include traditional open surgery and minimally invasive surgical treatment as well as needle knife surgery. If you find that your infant’s thumb is not flexible, you should seek medical advice and treatment under doctor’s guidance. Pay attention to rest on weekdays and avoid excessive use of hands.