Sitting up with a pain in the buttocks may be caused by sciatica bursitis, sciatica, osteophytes and other causes. In addition, physiological factors are also common and should not be ignored. 1. Sciatic Nodal Bursitis: Sciatic Nodal Bursitis mainly grows in the deeper position of the buttocks, close to the position of the sciatic nodes, when the patient is sitting, the sciatic nodes are often compressed, resulting in chronic irritation of the surface or the surrounding synovial bursa, which leads to sterile inflammation, and is mainly manifested as pain and other symptoms. 2. Sciatica: sciatica is a kind of sciatic nerve pathway and distribution area pain syndrome, mainly manifested as buttocks, thighs and calves radiating pain, the patient sitting up for the first time buttock pain may be caused by sciatica. 3. Osteomalacia: Osteomalacia, also known as bone spur, is a bony growth formed on the edge of the normal bone, which is mainly manifested as localized lumps, pain, limited activities and other symptoms, patients with osteomalacia in the buttocks may experience pain in the buttocks when sitting up. 4. Physiological reasons: common reasons such as the chair is too hard or sitting for too long, these factors may cause buttock pain. It is recommended that the patient should consult a doctor in time to get a clear cause for the targeted treatment, pay attention to rest in life, avoid strenuous activities, and pay attention to monitoring the condition and regular review.