The majority of arm extension is curable, resulting in the following common causes of arm extension, respectively, the corresponding treatment can make the arm straight, a. The most common is a variety of acute and chronic injuries, resulting in injury to the elbow joint, thus causing flexion deformity of the elbow joint, as long as the causative factors are removed, and appropriate functional exercise, the majority of the arm can be straightened. Another common reason is the stiffness of the elbow joint after the fracture due to prolonged external fixation, at this time most of the functional exercises can straighten the joint, but there are very few patients, due to heavy joint adhesions can not straighten. In this case, surgical release is required to straighten the elbow joint. In the case of congenital elbow flexion deformity, osteotomy is most often required to straighten the arm.