The arm fell, you can determine whether there is a fracture from the following aspects: first, listen to hear whether there is a bone rubbing sound, hold the ends of the limb with two hands, do anterior, posterior, left, right flexion and extension, spreading activities. If you can hear the fracture broken end of the click click click sound, indicating that the fracture occurred. Second, check for osteochondrosis, also called abnormal activity, that is, abnormal activity. The method of checking is to take the proximal end of the limb with one hand and the distal end of the limb with the other hand, and do forward, backward, inward and outward rocking and flexion and extension activities with force. If the backbone of the limb shows abnormal movement, i.e., flexion, extension, and spreading like a joint, it means that the bone has been broken and a fracture has occurred.