Pelvic Girdle - Skeletal Anatomy

Pelvic Girdle Overview

• The pelvic girdle, also known as the bony pelvis, comprises:

  • Right and left pelvic bones (os coxae), also referred to as hip bones and innominate bones.

    • Formed by the fusion of three bones:

      • Ilium

      • Ischium

      • Pubis

• The sacrum and coccyx form the posterior wall of the bony pelvis.

Functions of the Pelvis

• Protects lower abdominal and pelvic organs.

• Articulates with the bones of the lower extremities.

• Provides attachment sites for muscles and ligaments of the trunk and lower extremities.

Anatomical Features of the Pelvic Girdle

Anterior View

• Fused sacrum and coccyx

• Pelvic bones: right and left

• Obturator foramen: space enclosed by pelvic bones.

• Acetabulum: articulation point for the lower extremity.

• Pubic symphysis: cartilaginous pad connecting pelvic bones.

• Orientation: Indicate superior, inferior, medial-lateral orientations.

Medial View of Pelvic Bones

• Medial view: surface facing the pelvic viscera (internal/pelvic surface) with anterior-posterior orientation.

• Three bones forming the pelvic bone:

  • Ilium (superiorly)

  • Pubis (anteriorly)

  • Ischium (posteriorly)

• Obturator foramen: round space created by ischium and pubis.

• Features of the Ilium:

  • Iliac crest: bony ridge located at the waist.

  • Anterior superior iliac spine (ASIS) & Posterior superior iliac spine (PSIS): project downwards from iliac crest.

  • Anterior inferior iliac spine (AIIS) & Posterior inferior iliac spine (PIIS): located inferior to ASIS & PSIS, respectively.

  • Anchors muscles of the hip and thigh.

• Ala: broad flat portion below iliac crest.

• Iliac fossa: concave area giving a bowl shape to the pelvis.

• Articulation with sacrum:

  • Auricular surface: ear-shaped area for sacrum articulation.

  • Iliac tuberosity: roughened area for muscle attachment.

• Arcuate line: ridge sweeping from auricular surface to pubis.

• Linea terminalis: includes the arcuate and pectineal lines.

• Pectineal line: continues from arcuate line, ends at pubic tubercle.

• Symphyseal surface: attaches to the cartilaginous pubic symphysis.

• Superior and inferior pubic rami: straight bone portions connecting ilium and ischium, forming obturator foramen boundary.

Posterior Features of the Ischium

• Ischium features:

  • Ischial spine

  • Ischial tuberosity

  • Ischial ramus connecting to inferior pubic ramus.

• Notches created by ischial spine:

  • Greater sciatic notch (bound by PSIS)

  • Lesser sciatic notch

• Ligaments: cross over notches forming foramina.

Lateral Surface of the Right Pelvic Bone

• Outer surface features:

  • Anterior and posterior orientations reversed.

  • Acetabulum: cup-like depression for femur articulation (points laterally).

  • C-shaped lunate surface: smooth for femoral head articulation.

• Gluteal surface: lateral surface of the ala marked by gluteal lines indicating muscle attachment sites.

• Labeling: iliac spines, greater and lesser sciatic notches, ischial tuberosity.

Key Landmarks and Terminology

• Ilium Features:

  • Iliac crest, iliac fossa, ASIS, PSIS

• Ischium Features:

  • Ischial spines and tuberosity

  • Pain from ischial tuberosity inflammation.

• Pubis Features:

  • Pubic crest: lateral extension from pubic symphysis, continuous with pectineal line.

  • Pubic tubercle & pubic arch: anterior arch formed by union of pelvic bones.

Pelvic Brim and Inlet

• Pelvic brim: formed by superior edges of sacrum, arcuate and pectineal lines, pubic symphysis, enclosing the pelvic inlet.

• Pelvic inlet: circular opening between abdominal and pelvic cavities, dividing into false and true pelvis.

  • False Pelvis: superior portion containing lower abdominal viscera.

  • True Pelvis: inferior portion housing pelvic viscera and deep perineum.

• Pelvic outlet: diamond-shaped opening enclosed by pubic arch, ischial tuberosities, sacrotuberous ligaments, and sacrum.