Protruding bones at the back of the head are usually caused by two conditions: 1. Chondrosarcoma of the skull is common. This condition is mainly due to external collision of the bones in this position, or external stimulation or congenital factors, which can easily lead to the appearance of chondrosarcoma. If the pain and swelling is uncomfortable or affects the sleep at night, it is better to have surgery to avoid malignant change. 2. The back of the head has occipital bone and papillae on both sides, which are bony structures protruding outward, which is a normal physiological phenomenon. The bone protrusion at the back of the head usually shows different characteristics for different reasons, so it should be combined with whether there are other physical symptoms and discomfort for normal judgment, and it is necessary to do related medical examination to determine the cause before corresponding treatment.