Anatomy of the Pelvis-Basics

Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Bony Anatomy of the Pelvis

The pelvis is a ring-like bony structure that connects the spine to the lower limbs and supports pelvic organs.

Components of the Pelvis

1. Hip Bones (Innominate Bones) – Two large bones, each formed by fusion of:

   • Ilium

   • Ischium

   • Pubis

2. Sacrum

   • Triangular bone at the base of the spine

   • Formed by fusion of five sacral vertebrae

   • Transfers body weight to the pelvis

3. Coccyx

   • Terminal part of the vertebral column

   • Composed of fused coccygeal vertebrae

   • Serves as attachment for ligaments and muscles

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Ligaments of the Pelvis

Pelvic ligaments provide stability, limit excessive motion, and support pelvic organs by connecting the sacrum, ilium, ischium, and pubis.

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Anterior Pelvic Ligaments

1. Anterior Longitudinal Ligament

2. Anterior Sacroiliac Ligament

3. Sacrotuberous Ligament

4. Iliofemoral Ligament

5. Iliolumbar Ligament

6. Inguinal Ligament

7. Sacrospinous Ligament

8. Obturator Membrane

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Posterior Pelvic Ligaments

1. Dorsal Sacroiliac Ligament

   • Major stabilizer of the sacroiliac joint

2. Supraspinous Ligament

3. Sacrotuberous Ligament

4. Sacrospinous Ligament

5. Iliolumbar Ligament

6. Articular Capsule of the Hip Joint

7. Deep Dorsal Sacrococcygeal Ligament

8. Superficial Dorsal Sacrococcygeal Ligament

9. Arcuate Pubic Ligament

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Muscles Present in the Pelvis

These muscles contribute to hip movement, pelvic stability, and rotation of the lower limb.

1. Piriformis

2. Superior Gemellus

3. Obturator Internus

4. Inferior Gemellus

5. Quadratus Femoris

6. Obturator Externus

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Arteries of the Pelvis

Major blood supply to pelvic organs and lower limb originates from iliac vessels.

1. Common Iliac Artery

2. External Iliac Artery

3. Internal Iliac Artery

4. Pudendal Artery

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Veins of the Pelvis

Venous drainage mirrors the arterial system.

1. External Iliac Vein

2. Internal Iliac Vein

3. Common Iliac Vein

4. Deep Circumflex Iliac Vein

5. Lateral Sacral Vein

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Nerves of the Pelvis

Pelvic nerves supply the lower limb, pelvic floor, and perineum.

1. Pudendal Nerve

2. Obturator Nerve

3. Iliohypogastric Nerve

4. Ilioinguinal Nerve

5. Genitofemoral Nerve

6. Lateral Cutaneous Nerve of Thigh

7. Superior Gluteal Nerve

8. Sciatic Nerve

9. Superior Cluneal Nerves

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Joints of the Pelvis

Pelvic joints provide a balance between stability and limited mobility.

1. Sacroiliac Joint

2. Sacrococcygeal Joint

3. Lumbosacral Joint

4. Pubic Symphysis

5. Hip Joint

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Key Take-Home Points

• The pelvis acts as a load-bearing ring

• Stability is mainly ligamentous rather than muscular

• Internal iliac vessels are the primary supply to pelvic organs

• Pelvic nerves are clinically important in trauma, childbirth, and surgery

• Hip joint is the most mobile joint of the pelvis