The greater sciatic notch is a deep concavity on the posterior border of the ilium and ischium, converted into the greater sciatic foramen by the sacrospinous and sacrotuberous ligaments. The piriformis muscle passes through the greater sciatic foramen, dividing it into suprapiriform and infrapiriform spaces. The suprapiriform space transmits the superior gluteal vessels and nerve; the infrapiriform space transmits the sciatic nerve, inferior gluteal vessels and nerve, internal pudendal vessels, pudendal nerve, and the nerves to obturator internus and quadratus femoris.
The greater sciatic notch is the key landmark for posterior hip joint injection and sciatic nerve block. In piriformis syndrome, the sciatic nerve is compressed within the greater sciatic foramen below the piriformis, producing buttock and posterior leg pain mimicking lumbar disc herniation. A bipartite pyriformis with a sciatic nerve variant passing through the muscle is a recognised anatomical predisposition. In pelvic fractures, the greater sciatic notch level determines fracture classification and surgical approach. Posterior acetabular column fractures are approached through this notch.
Compression of the sciatic nerve within the infrapiriform space from piriformis muscle spasm, hypertrophy, or anatomical nerve variants produces posterior hip and buttock pain radiating down the posterior leg, reproduced by piriformis stretch tests, treated by physiotherapy, injection, or surgical piriformis release.
Posterior column acetabular fractures disrupting the greater sciatic notch can lacerate the superior gluteal artery as it exits the suprapiriform foramen, causing massive retroperitoneal haemorrhage requiring emergency embolisation.
