Sacroiliac fascial fat hernia is a type of hernia formed by hip fat protruding through the sacroiliac fascia, which is one of the causes of low back pain. It is more common in women, especially obese adult women, and relatively rare in men. The presence of an intrinsic foramen ovale in the sacroiliac fascia above the external sacroiliac joint is the pathologic basis for the development of this disease. Pathogenesis The sacroiliac fascia above the sacroiliac joint is relatively weak, by the lumbar 1 ~ 3 nerves composed of the posterior branch of the gluteal epithelial nerve and the accompanying vascular bundles in the formation of the intrinsic foramen ovale across the sacroiliac joint above the sacroiliac fascia, and the localization of the relatively abundant adipose tissue, especially in obese women, when strenuous stooping activities or the gluteus maximus muscle contracted violently, the deep adipose tissue pressure increases, the intrinsic foramen ovale through the weak hernia or the hernia after tearing of the fascia. A fat hernia is formed when the fascia is torn. Herniated fat edema, hemorrhage, torsion, incarceration or compression of the nearby cutaneous nerve can cause local pain and sensory pain in the distribution area of the anterior branch of the lumbar nerve in the corresponding segment. There are differences in the size of the hernia hole and the amount of hernia content, and the nature of the pain. If the onset time is short and the content is small, it can be returned by itself, on the contrary, it is difficult to return the herniated adipose tissue to the surrounding tissues, forming a local painful nodule, then the pain is obvious, and it often produces the symptoms of chronic low back and leg pain. In addition, the hernia from the intrinsic foramen, due to the nerve and blood vessel routes, the pain is heavier, while the hernia from the non-intrinsic foramen is less painful. Symptoms and signs The main symptoms are low back pain and hip pain on the affected side. Partial sacroiliac fascial fat is a type of hernia formed by hip fat protruding through the sacroiliac fascia, which is one of the causes of low back and leg pain. It is more common in women, especially obese adult women, and relatively rare in men. The presence of an intrinsic foramen ovale in the sacroiliac fascia above the outer sacroiliac joint is the pathologic basis for the development of this disease. Patients with inductive sciatica, the degree of which varies greatly, most of the soreness and pain, a few in the bending, squatting, getting up or sacroiliac, lumbar twisting flash after the pain suddenly intensified, and even turn over, get up and other activities are limited.