Dense sacroiliac arthritis is usually seen in women aged 20 to 40 years old, patients with recurrent lower back pain, sometimes radiating down to both buttocks and thighs, but not radicular pain, the symptoms can be aggravated by lower back activities, often with a history of recent childbirth. 1. Diagnosis 1. Clinical manifestations: chronic and persistent pain in the lower back, or pain at the pubic symphysis, and may radiate to the buttocks and posterior femur, the pain is generally mild. Female patients often have increased pain in the lower back due to the increase in menstrual cycle and pregnancy, but there is no sign of nocturnal pain, and the movement of the lower back is basically unrestricted. Some patients may have no conscious symptoms, but are only occasionally found in the X-ray examination for other reasons. 2. Clinical examination: there are limited pressure pain points near the sacroiliac joint or the lesion site, and local muscle spasm. The lumbar movement, straight leg raise test “4” test and so on are basically normal. 3.What is seen on X-ray: The main manifestation is unclear structure of the auricular surface of the iliac bone, the bone is uniformly dense, its inner edge is bounded by the sacroiliac joint and does not invade the articular surface, its outer edge constitutes a clear straight line or arc, constituting the osteosclerotic area of the lesion part into a variety of different forms, which can be broadly divided into triangular, crescent-shaped and pear-shaped. Most of the lesions invade all or the upper and lower 2/3 of the auricular surface. Most of the lesions are bilateral, and the size and shape of the lesions may be asymmetric, while a few are unilateral. If the lesion is in the lumbar spine, it can be seen that the anterior superior horn of the lumbar vertebral body has increased bone density, and the vertebral space is clear and unchanged. 4, diagnosis basis: young women, chronic and persistent lower back pain, recurrent, with periodic changes, especially in the postpartum lower back pain symptoms aggravated, should be suspected of this disease, but the final diagnosis of the disease or rely on X-ray examination to confirm the diagnosis. Second, treatment measures 1, physiotherapy, injection and drug conservative treatment; 2, reduce activity, if necessary, bed rest for 2-4 weeks; 3, symptom reduction before bed activity can be protected with lumbar circumference; 4, conservative treatment is not effective can be taken to remove the lesion or sacroiliac joint fixation.