HIP BONE ANATOMY

HIP BONE OVERVIEW

• The hip bone is a large, flattened, irregularly shaped bone that is constricted in the center and expanded above and below
• Articulates with the opposite hip bone to form the pelvic girdle, providing support and stability to the lower body

Ischiopubic Ramus

• Located where the inferior ramus of the ischium joins the inferior ramus of the os pubis
• Forms part of the boundary of the obturator foramen
• Attachment point for muscles of the perineal region and locomotion

Obturator Foramen

• Location: Between the ischium and os pubis
• It is large and oval in males; smaller and triangular in females
• Covered by the obturator membrane
• Contains a ligament forming a canal for the obturator vessels and nerve

Greater Sciatic Notch

• Location: Beneath the posterior inferior spine of the ilium
• It is a passageway for key neurovascular structures

Greater Sciatic Foramen

• Created by the greater sciatic notch and sacrospinous ligament
• Allows passage of important nerves and vessels

HIP BONE COMPONENTS

• The hip bone consists of three main components: the ilium, ischium, and os pubis, that fuse in adulthood taking part in the formation of the acetabulum

Ilium

• It is a broad, expanded portion of the hip bone
• Divided into:
  • Body: Forms part of the acetabulum
  • Ala: Large expanded portion forming the greater pelvis

Ischium

• Lowest part of the hip bone
• Consists of a body and superior and inferior rami
• Contributes over two-fifths of the acetabulum
• Forms the walls of the lesser pelvis

Os Pubis

• Forms part of the acetabulum (one-fifth of its structure)
• Articulates with the opposite os pubis at the pubic symphysis
• Divided into:
  • Body
  • Superior Ramus
  • Inferior Ramus

Acetabulum

• Location: Middle of the outer surface of the hip bone
• Structure:
  • Large, cup-shaped articular cavity
  • Formed by the ilium, ischium, and os pubis
  • Prominent rim surrounds the acetabulum
• Features:
  • Lunate Surface: Articulates with the head of the femur
  • Acetabular Fossa: Non-articular, located at the bottom

ACETABULUM

• The acetabulum is formed by the union of three bones: the ilium, ischium, and os pubis
• Features a prominent, uneven rim known as the acetabular margin
• Comprises two key components: the lunate surface (articular) and the acetabular fossa (non-articular)

Acetabular Margin

• Robust, uneven rim surrounding the acetabulum
• Thick and strong above
• Attachment site for the glenoidal labrum

Acetabular Fossa

• Non-articular depression at the base of the acetabulum
• Attachment site for the ligamentum teres

Acetabular Notch

• Deep indentation below the acetabular fossa
• Converted into a foramen by the transverse acetabular ligament

Lunate Surface

• Curved, smooth, articular surface
• Forms the majority of the acetabulum
• Articulates with the head of the femur

ILIUM

• The ilium is a broad, expanded portion of the hip bone extending upward from the acetabulum
• Divided into the body and the ala
• The body forms part of the acetabulum and transitions into the arcuate line
• The ala (wing) expands outward with gluteal and sacropelvic surfaces

Arcuate Line

• Located on the internal surface of the ilium
• Separates the body and the ala of the ilium

Ala of the Ilium

• The ala is a large, wing-like portion of the bone
• Features an external surface and an internal surface
• Includes the crest as well as anterior and posterior borders

Iliac Crest

• A convex, sinuously curved structure, concave in front and convex behind
• Consists of the outer lip, intermediate zone, and inner lip
• Thinner at the center than at the extremities
• Provides support and serves as an attachment point for muscles and ligaments

• Outer lip of iliac crest: Outermost part providing attachment to muscles
  • Iliac tubercle: Prominent bony landmark ~5 cm posterior to the anterior superior iliac spine
• Intermediate zone: Located between the inner and outer lips
• Inner lip of iliac crest: Most medial part of the crest; attachment site for several muscles

Iliac Spines

• Anterior superior iliac spine: Prominent projection at the junction of the iliac crest and anterior border; attachment point for several muscles
• Anterior inferior iliac spine: Located below the anterior superior iliac spine and notch; attachment point for important structures
• Posterior superior iliac spine: Projection serving as an anchorage point for the long posterior sacroiliac ligament
• Posterior inferior iliac spine: Located below the posterior superior iliac spine; forms the upper boundary of the greater sciatic notch

Iliac Fossa

• It has a smooth, concave surface
• Gives origin to the Iliacus muscle

Gluteal Surface of Ilium

• Directed backward and laterally behind, and laterally and downward in front
• Smooth, convex in front, concave behind
• Crossed by three lines

Gluteal Lines

• Anterior gluteal line: Longest of the gluteal lines; starts at the iliac crest ~4 cm behind its anterior extremity; curves backward and downward, ending at the upper part of the greater sciatic notch
• Posterior gluteal line: Shortest of the gluteal lines; starts at the iliac crest ~5 cm in front of its posterior extremity; ends at the upper part of the greater sciatic notch
• Inferior gluteal line: Least distinct of the gluteal lines; starts at the notch on the anterior border of the ilium; curves backward and downward, ending near the middle of the greater sciatic notch

Sacropelvic Surface of Ilium

• Rough surface behind the iliac fossa
• Shape resembles the auricula (external ear)
• Articulates with the sacrum

Iliac Tuberosity

• Situated in the superior portion of this area
• Elevated and rough
• Attachment site for a ligament

ISCHIUM

• The ischium forms more than two-fifths of the acetabulum
• Contributes to the lunate surface and acetabular fossa

Body of Ischium

• Forms a little more than two-fifths of the acetabulum
• Its external surface contributes to the lunate surface and the acetabular fossa

Ramus of the Ischium

• Extends from the body of the ischium
• Contributes to the formation of the obturator foramen

Ischial Tuberosity

• Formed by the posterior surface of the superior ramus
• Divided into:
  • A rough and triangular lower portion
  • A smooth and quadrilateral upper portion

Ischial Spine

• A pointed, triangular eminence extending backward and medially from the ischium
• Attachment site for important structures

Lesser Sciatic Notch

• Located below the ischial spine
• Converted into the lesser sciatic foramen by ligaments
• Allows passage of specific muscles, nerves, and vessels

OS PUBIS

• The pubis forms one-fifth of the acetabulum
• Contributes to the lunate surface and acetabular fossa
• Its internal surface also forms part of the wall of the lesser pelvis

Pubic Tubercle (Pubic Spine)

• Prominent projection on the upper border of the pubis
• Serves as an attachment point for the inguinal ligament

Pubic Crest

• Location: Medial to the pubic tubercle, extending to the medial border
• Attachment site for several muscles

Superior Ramus

• Extends from the body of the pubis to the median plane
• Articulates with the opposite superior ramus to form the pubic symphysis

Iliopubic Eminence

• Located at the junction of the ilium and pubis
• Attachment site for the iliacus muscle

Pecten Pubis

• Well-defined ridge above the pubic tubercle
• Forms part of the brim of the lesser pelvis

Obturator Crest

• Anterior margin of the superior ramus
• Extends from the pubic tubercle to the acetabulum
• Forms part of the circumference of the obturator foramen

Obturator Groove

• Located on the inferior aspect of the superior ramus
• Forms part of the upper boundary of the obturator foramen
• Features two tubercles:
  • Anterior Obturator Tubercle: Located anteriorly; serves as a landmark in the pelvic region
  • Posterior Obturator Tubercle: Located posteriorly; attachment site for the obturator membrane

Inferior Pubic Ramus

• Thin, flattened portion of the os pubis
• Extends laterally and backward
• Connects with the inferior ramus of the ischium below the obturator foramen