e. Posterior Inferior Iliac Spine (Spina iliaca posterior inferior) is a curvature found inferior to the posterior superior iliac spine. The two spines are separated by a small notch. A ligament that binds the ilium to the sacrum attaches here.
f. Iliac Fossa (Fossa iliaca) is a broad depression located along the anteromedial surface, inferior to the iliac crest. It is an attachment point for the iliacus muscle.
g. Iliac tuberosity (Tuberositas iliaca) is a roughened area located inferior to the crest and posterior to the iliac fossa. The posterior sacroiliac ligaments and the sacrospinalis and multifidus muscles attach here.
h. Auricular surface (Facies auricular ossis ilii) is a L-shaped or ear-shaped roughened surface situated inferior to the tuberosity. This area articulates with auricular surface of sacrum to form the sacroiliac joint.
i. Arcuate line (Linea arcuata) is a curved ridge that forms the inferior boundary of the iliac fossa. It also delinates the boundary between the body and the wing (large expanded portion; ala) of the ilium.
Pubic Bone (Pubis) Markings.
j. Symphysis pubis or pubic symphysis (Symphysis pubica; symphysis pubis) is the cartilaginous joint between the two pubic bones.
k. Body of pubis (Corpus ossis pubis) is the flatten, medial end of the pubis that lies adjacent to the symphysis.
l. Inferior pubic ramus (Ramus inferior ossis pubis) is a thin, flat extension from the medial pubis that joins the ischial ramus. The adductor brevis, adductor magnus, and gracilis muscles attach along this surface.
m. Superior pubic ramus (Ramus superior ossis pubis) is a band of bone that runs along the superior aspect of the pubis. It is an attachment point for the pectineus muscle.
n. Pectineal line (Linea pectinea; pecten ossis pubis) is a sharp ridge that runs along the superior margin of the superior pubic ramus. This area, which is also called the pecten pubis, is an the attachment point for the pectineus muscle.
o. Pubic crest (Crista pubica) is a short, superiomedial ridge that runs extends horizontally from the symphysis to the pubic tubercle. It is an attachment point for the abdominal muscles.
p. Pubic tubercle (Tuberculum pubicum) is a projection from the lateral end of the pubic crest that serves as an attachment point for the inguinal ligament.
Ischium Bone Markings.
q. Ischial tuberosity (Tuber ischiadicum) is a roughened, curved eminence located at the junction of the posterior and inferior borders of the ischium. It supports the weight of the body when sitting and serves as an attachment point for the sacrotuberous ligament and the hamstring muscles, quadratus femoris muscle, and inferior gemellus muscle.
r. (Inferior) Ramus of Ischium (Ramus ossis ischii) is an anterior extension from the ischial tuberosity that joins the inferior pubic ramus. The adductor magnus and obturator externus muscles attach to this surface.
s. Ischial Spine (Spina ischiadica) is a sharp projection from the posterior margin of the ischium. It is an attachment point for the sacrospinous ligament.
t. Lesser Sciatic Notch (Incisura ischiadica minor) is a indentation located below the spine. The sacrotuberous and sacrospinous ligaments transform the notch into the lesser sciatic foramen, which allows the obturator internus tendon and nerve, internal pudendal vessels, and pudendal nerve to pass.
Interdivisional Bone Markings.
u. Greater Sciatic Notch (Incisura ischiadica major) is a large indentation located below the posterior inferior iliac spine. The sacrotuberous and sacrospinous ligaments transform the notch into the greater sciatic foramen, which allows the passage of the performs muscle, 7 nerves (including the sciatic nerve), and 3 sets of blood vessels.
v. Obturator Foramen (Foramen obturatum; foramen obturatorium) is a large anterior opening enclosed by the pubic and ischial rami. The foramen, which is mostly covered by a ligamentous membrane, helps decrease the weight of the os coxae. The obturator vessels and nerves pass through a large canal in the upper portion of the membrane.