2 months old baby arm joint ringing is mainly due to the immature development of infant joints, ligaments are relatively loose, the joint gap is relatively large, and there is no ossification phenomenon. Therefore, in the process of the child’s activities, because the range of activities is relatively large, so that the cartilage and cartilage, and joint activity space may have collision and friction, and thus emit a loud sound. This is a common occurrence in infants and children, so parents should not be anxious. Usually, as children develop, their tendons and ligaments mature and ossification is established, the joint ringing will gradually disappear and no special treatment is needed. If other abnormalities occur, such as joint pain and swelling, you can go to the hospital promptly.