Dense osteitis of the ilium is a non-specific inflammatory disease characterized by osteosclerosis, with highly dense osteosclerosis, especially in the lower two thirds of the ilium, but no change in the joint space. Because it is located in the sacroiliac joint, and the symptoms of this joint are obvious, so it is also called “sacroiliac joint dense osteitis”. More than 90% of the patients are middle-aged women, and the disease is common in late pregnancy, especially after delivery, and can also be seen after chronic infection of the urinary tract or female adnexa, or other infections in the pelvic cavity. In addition, trauma to the hip-sacral area may also induce or cause the disease. 2. Clinical manifestations of dense sacroiliitis (1) It is more common in women, 20 to 40 years old and middle-aged women. (2) Recurrent lower back pain, sometimes radiating down to both hips and thighs, but not radicular pain, and the symptoms can be aggravated by lower back activities, which is thought to be a kind of self-healing disease; (3) There is often a history of recent labor and delivery; (4) Some patients are asymptomatic and only found during physical examination. Physical examination: (1) Knocking pain and pressure pain in the sacroiliac joints; (2) Pelvic separation and compression test, “4” test and Gay’s test are all positive. 4.Imaging manifestations: Non-specific inflammation characterized by osteosclerosis on the iliac side of the sacroiliac joint, with highly dense osteosclerosis, especially more obvious in the lower 2/3 of the ilium, but no change in the joint space. Because it is located in the sacroiliac joint, and the symptoms of this joint are obvious, so it is also called “sacroiliac joint dense osteitis”. Pathology: Pregnancy, childbirth and trauma can cause tearing of sacroiliac joint ligaments, which can easily block the local blood supply. Therefore, early local congestion, edema and exudation increase, and gradually local hyperplasia and degeneration reaction, with the densification of collagen fibers to sclerosis; blood vessels form thick-walled blood vessels, easy to be occluded and cause ischemia and hypoxia at the auricular surface of the iliac bone, and sclerotic changes in the bone, so that the local bleeding during the operation is less. The sacroiliac joint capsule wall showed fibroplasia, decreased elasticity and loosening-like changes. Those secondary to pelvic inflammation also show similar pathologic changes, which may be caused by bacterial endotoxin. (1) Mild: tight pants, some scholars report that the early use of shifted ginseng (white ginseng, 3 points per day, for 1 to 2 months) can be cured or improved, but not verified by the author. (2) Serious cases: affecting walking and workers, sacroiliac joint fusion is feasible. Generally, only the upper joint can be fused, do not need the whole joint fusion, so as not to accidentally injure the superior gluteal artery and cause serious consequences. (3) A variety of non-surgical therapies, such as traditional Chinese medicine, physiotherapy, massage, acupuncture, cupping and non-steroidal anti-inflammatory drugs can be used.