Articulations of the Pelvis

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Anatomy > Gray's Anatomy of the Human Body > III. Syndesmology > 5i. Articulations of the Pelvis

Henry Gray (1821–1865). Anatomy of the Human Body. 1918.

Articulations of the Pelvis

File:Gray322.png

FIG. 322—Anterior sacral segment (coronal section)

File:Gray323.png

FIG. 323—Middle sacral segment (coronal section)

The ligaments connecting the bones of the pelvis can be grouped into:

• Ligaments between the sacrum and ilium
• Ligaments between the sacrum and ischium
• Ligaments between the sacrum and coccyx
• Ligaments between the two pubic bones

1. Sacroiliac Articulation (Articulatio sacroiliaca)

This amphiarthrosis occurs between the auricular surfaces of the sacrum and ilium, with intervening cartilage—thicker on the sacral side. These surfaces are closely united by fibrocartilage and interosseous fibers, and occasionally present a synovial joint cavity, giving it diarthrodial characteristics.

Ligaments of the Sacroiliac Joint

• Anterior sacroiliac ligament – Thin bands uniting the anterior surfaces
• Posterior sacroiliac ligament – A strong band in a posterior groove, consisting of:
  • Short (horizontal) fibers from sacrum to ilium
  • Long (oblique) fibers from sacrum to posterior superior iliac spine
• Interosseous sacroiliac ligament – Deep, short, strong fibers between the sacral and iliac tuberosities

2. Sacroischial Ligaments

These include:

• Sacrospinous ligament – Triangular, from ischial spine to sacrum and coccyx
• Sacrotuberous ligament – From sacrum and coccyx to ischial tuberosity; forms the falciform process and gives origin to part of the biceps femoris

Function and Boundaries

These ligaments convert the greater sciatic notch and lesser sciatic notch into foramina.

• Greater sciatic foramen – Transmits the piriformis muscle, sciatic nerve, superior gluteal nerve, inferior gluteal nerve, and more
• Lesser sciatic foramen – Transmits the obturator internus tendon and internal pudendal vessels

3. Sacrococcygeal Symphysis

An amphiarthrosis between the sacrum and coccyx, with a fibrocartilaginous disk. Ligaments include:

• Anterior sacrococcygeal ligament – Thin anterior bands
• Posterior sacrococcygeal ligament – A flat posterior band completing the lower sacral canal
• Lateral sacrococcygeal ligament – Connects coccygeal transverse process to sacrum
• Interarticular ligaments – Unite the cornua of the two bones

4. Pubic Symphysis (Symphysis pubica)

An amphiarthrosis formed between the two pubic bones, supported by:

• Anterior pubic ligament
• Posterior pubic ligament
• Superior pubic ligament
• Arcuate pubic ligament
• Interpubic fibrocartilaginous lamina – May contain a cavity; prominent in females

File:Gray321.png

FIG. 321—Coronal section of the symphysis pubis. (Gray's Anatomy)

Articulations of the Pelvis

Mechanism of the Pelvis

The pelvis serves to:

• Support and transmit the weight of the upper body
• Provide attachment surfaces for muscles
• Protect pelvic organs

Weight Transmission

The weight from the vertebral column is transmitted through:

• The sacroiliac joints
• The acetabulum and pubic symphysis

The sacrum acts as a wedge, stabilizing the pelvis against:

• Downward & backward thrust (resisted by wedge shape)
• Downward & forward thrust (resisted by interosseous and posterior sacroiliac ligaments)

File:Gray324.png

FIG. 324—Posterior sacral segment (coronal section)

Sacral Segments

• Anterior segment – Slightly wedge-shaped; almost parallel articular surfaces
• Middle segment – Strong wedge-shaped with locking ridges
• Posterior segment – Reverse wedge shape; less interlocking

Movement and Pregnancy Adaptation

• Rotation occurs along an axis through the middle segment
• During pregnancy, pelvic ligaments relax, increasing mobility
• The sacrotuberous ligament and sacrospinous ligament check sacral displacement during delivery

See Also

• Pelvic girdle
• Sacrum
• Sacroiliac joint
• Coccyx
• Pubic symphysis
• Pelvic cavity

Gray's Anatomy

• Gray's Anatomy Contents
• Gray's Anatomy Subject Index
• About Classic Gray's Anatomy
• Glossary of anatomy terms

Anatomy atlases (external)

[1] - Anatomy Atlases

Adapted from the Classic Grays Anatomy of the Human Body 1918 edition (public domain)