Innominate Documentation – Anatomy Software


·         The innominate/hip bone is a large, flattened, irregular shaped bone, constricted in the center and expanded above and below


·         It consists of three parts, the ilium, ischium, and pubis



  1. Ilium

·         It presents two surfaces—an external  (Gluteal surface )and an internal (iliac fossa)—a crest, and two borders; anterior and posterior

·         This  external surface is crossed in an arched direction by three lines: the posterior, anterior, and inferior gluteal lines

·         The internal surface of the ilium is bounded above by the crest, below, by the arcuate line; in front and behind, by the anterior and posterior borders.



    1. Gluteal lines:

                                                              i.      Posterior

·         Shortest of the three lines.

·         Begins at the crest, about 5 cm. in front of the PSIS and runs downward to the upper part of the greater sciatic notch.

·         Behind this line is a narrow semilunar surface, gives origin to the gluteus maximus.


                                                            ii.      Anterior

·         Longest of the three lines.

·         Begins at the crest, about 4 cm. behind the ASIS, and, taking a curved direction downward and backward ending at the upper part of the greater sciatic notch.

·          The space between the anterior and posterior gluteal lines and the crest is concave, and gives origin to the gluteus medius.


                                                          iii.      Inferior

·         Least distinct of the three lines.

·         Begins in front at the notch on the anterior border between ASIS and AIIS, curving backward and downward ending near the middle of the greater sciatic notch.

·         The surface of bone above the line gives origin to the gluteus minimus.


    1. iliac fossa

·         It presents a large, smooth, concave surface, which gives origin to the Iliacus.


    1. auricular surface

·         Resembles the shape of an ear.

·         Covered with hyaline cartilage.

·         Articulates with a similar surface on the side of the sacrum to form the SI joint.


    1. iliac tuberosity

·         Rough for the attachment of the posterior sacroiliac and interosseous ligaments and for the origins of the sacrospinalis and  multifidus.


    1. iliac crest

·         Is convex in outline but is sinuously curved, being concave inward in front, concave outward behind.

·         Ends in the anterior (ASIS) and posterior (PSIS) superior iliac spines.


    1. tubercle of crest

·         It is a prominent tubercle on the outer lip of the iliac crest.

·         About 5 cm. posterior to the anterior superior iliac spine (ASIS).


    1. ASIS

·         The uppermost projection of the anterior border.

·         Gives attachment to the inguinal ligament and the sartorius.


    1. AIIS

·         The lowermost projection of the anterior border.

·         Ends in the upper lip of the acetabulum.

·         Gives attachment to the straight tendon of the rectus femoris and to the iliofemoral ligament of the hip-joint.


    1. PSIS

·         The uppermost projection of the posterior border.

·         Gives attachment to the oblique portion of the posterior sacroiliac ligaments and the multifidus.


    1. PIIS

·         The lowermost projection of the posterior border.

·         Below the PIIS is the greater sciatic notch.


    1. greater sciatic notch

·         The posterior border of the iliac crest after the PIIS forms the upper part of a large notch.

·         Its lower border is continuous with the ischial spine.


    1. lesser sciatic notch

·         A small notch below the ischial spine.

·         Bounded by the ischial spine above and the ischial tuberosity below.


    1. arcuate line

·         it is a curved line.

·         It divides the ilium into two parts, the body and the ala on the internal surface.


    1. iliopubic eminence

·         A gentle elevation that marks the point of union of the ilium and pubis.



  1. Ischium

·         Forms the lower and back part of the hip bone.

·         It is divisible into three portions—a body and two rami.


    1. ischial tuberosity

·         Divided into two portions: a lower, rough, triangular part and an upper, smooth, quadrilateral portion.

·         The lower portion is subdivided by a prominent longitudinal ridge, passing from base to apex, into two parts.

·         The outer gives attachment to the adductor magnus, the inner to the sacrotuberous ligament.

·         The upper portion is subdivided into two areas by an oblique ridge, which runs downward and outward; from the upper and outer area the semimembranosus arises; from the lower and inner, the long head of the biceps femoris and the semitendinosus.


    1. ischial spine

·         The posterior border forms a sharp well defined triangular projection.

·         Located between the greater and lesser sciatic notches.



  1. Pubis

·         The body forms one-fifth of the acetabulum, contributing by its external surface both to the lunate surface and the acetabular fossa.

·         Its internal surface enters into the formation of the wall of the lesser pelvis and gives origin to a portion of the obturator internus.


    1. pubic crest

·         Medial to the pubic tubercle is the crest, which extends from this process to the medial end of the bone (pubic symphysis).


    1. pubic tubercles

·         The upper border presents a prominent tubercle which projects forward.

·         Lateral on each side to the pubic crest.



    1. pectineal line

·         Passing upward and lateral from the pubic tubercle is a well-defined ridge.

·         Found along the superior edge of the superior pubic ramus.


    1. superior ramus (iliopubic ramus)

·         The superior ramus extends from the body superior and lateral toward the anterior border.


    1. inferior ramus (ischiopubic ramus)



  1. Acetabulum


    1. Notch

·         The margin of the acetabulum shows an inferior deep notch.

·         The notch is converted into a foramen by the transverse ligament.



    1. fossa

·         The floor of the acetabulum shows a non-articular area at the bottom of the cavity.



  1. Obturator Foramen

·         A foramen which is bounded by the different parts of the pubis, ischium and ilium.

·         A large aperture, situated between the ischium and pubis.

·         In the male it is large and of an oval form.

·         In the female it is smaller, and more triangular.


  1. Sacroiliac Joint

·         Is an amphiarthrodial joint, formed between the auricular surfaces of the sacrum and the ilium.


·         Supported by ligaments: The Anterior Sacroiliac, The Posterior Sacroiliac and the Interosseous Sacroiliac ligaments.