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Pelvis and hip joint

Last updated: July 21, 2021

Summarytoggle arrow icon

The bony pelvis (pelvic girdle) is composed of the two hip bones, the sacrum, and the coccyx. These bones are firmly connected by the pubic symphysis anteriorly and the sacrococcygeal and sacroiliac joints posteriorly. Each hip bone consists of three fused bones: the ilium, ischium, and pubis. In female individuals, the pelvis additionally accommodates the birth canal and therefore is larger and wider than in male individuals. The pelvic girdle transmits body weight from the axial skeleton to the lower extremities and provides attachment to a large number of muscles and ligaments. The pelvic cavity is the space within the pelvic girdle; it contains abdominal and pelvic organs, which are protected by the pelvic girdle. Located in the space within pelvic girdle is the pelvic cavity, which provides protection for abdominal and pelvic organs. Anatomical spaces of the pelvic cavity (e.g., rectouterine pouch, rectovesical pouch) vary between male and female individuals because of their different reproductive organs. Located inferior to the pelvic cavity is the pelvic floor, a complex fibromuscular structure that prevents pelvic organ prolapse, helps maintain fecal and urinary continence, and separates the perineal region from the pelvic cavity. Openings in the pelvic floor allow for the passage of the rectum, vagina, and urethra. The gluteal region consists of the muscles that form the buttocks, which can be divided into a superficial and a deep muscle layer. The superficial gluteal muscles abduct and medially rotate the thigh, while the deep gluteal muscles are responsible for lateral rotation of the thigh. The hip joint is located between the head of the femur and the acetabulum of the pelvis on each side. It connects the trunk to the lower extremities and supports dynamic and static body weight. The arterial supply of the femoral head is ensured by the foveolar artery and branches of the deep femoral artery. Movements of the hip joint include flexion, extension, lateral and medial rotation, abduction, adduction, and circumflexion.

The pelvis (pelvic girdle)

The hip joint

Bones of the pelvis

Hip bones

Overview of the hip bones
Bones Landmarks Anatomic features
Ilium
Ischium
Pubis

The anterior superior iliac spine helps to determine the course of the inguinal ligament. It also aids in the identification of the McBurney and Lanz points, which are important anatomical areas where localized tenderness is indicative of appendicitis.

Sacrum and coccyx

For information on the sacrum and coccyx, see “Gross anatomy” in “Vertebral column.”

Pelvic inlet

Pelvic outlet

Pelvic form and pelvic diameters

For information on the pelvic form and diameters, see the section “Birth canal” below.

Differences between the male and female pelvis

Overview of differences between the male and female pelvis
Male Female
Bones Bigger, thicker, and heavier Smaller, thinner, and lighter
Sacrum Longer and narrower Shorter and wider
Pelvic cavity Narrower and deeper Wider and shallower
Pelvic inlet Heart-shaped Oval-shaped
Pelvic outlet Smaller pelvic outlet; the ischial tuberosities face more medially Larger pelvic outlet; everted ischial tuberosities
Obturator foramen Round Triangular or oval
Subpubic angle Smaller (< 90°) Larger (> 90°)

Joints of the pelvis

Ligaments of the pelvis

For information on the ligaments of the hip joint, see “Hip joint” below.

Foramina of the pelvis

The pelvis contains many openings that allow the passage of nerves, vessels, muscles, and lymphatics.

Overview of foramina of the pelvis
Foramen Anatomy Structures passing through
Greater sciatic foramen
Lesser sciatic foramen
Obturator foramen
Pudendal canal
Vascular lacuna
Muscular lacuna

Pelvic cavity

Pelvic spaces

The pelvic spaces include peritoneal spaces located within the pelvic cavity and extraperitoneal anatomical spaces of the pelvic cavity. They vary significantly between male and female individuals due to their different reproductive organs.

Pelvic form

  • Gynecoid (most common female form): transverse oval inlet, wide sacrum, wide sacrosciatic notch, straight side walls, wide subpubic angle
  • Anthropoid (common in male individuals): long anterior-posterior diameters, short transverse diameters, wide sacrosciatic notch, narrow subpubic angle
  • Android (most common male form): triangular inlet, converging side walls, narrow sacrosciatic notch, narrow subpubic angle
  • Plateylpelloid (flat variation of gynecoid type): short anterior-posterior diameters, long transverse diameters, narrow sacrosciatic notch, wide subpubic angle

Pelvic regions

Pelvic planes

  • Plane of the pelvic inlet (angle of pelvic inclination): at the level of the pelvic brim boundaries; forms an angle of 55° with the horizon
  • Plane of greatest pelvic dimension (mid-cavity): at the level of the posterior surface of the pubic symphysis and the junction of the 2nd and 3rd sacral vertebra
  • Plane of least pelvic dimension (obstetric outlet): at the level between the anterior lower edge of the symphysis pubis and the tip of the sacrum posteriorly
  • Plane of the anatomical outlet: at the level of the anatomical pelvic outlet boundaries

Soft tissue structures

Pelvic floor

Layers of the pelvic floor

Pelvic diaphragm

Muscles of the pelvic diaphragm
Muscle Origin Insertion Innervation Function

Levator ani

Puborectalis
  • Forms a U-shaped sling around the lower rectum
  • Some medial fibers form another sling around the urethra (and vagina in female individuals).
  • Aids in fecal continence by maintaining the anorectal angle
  • Relaxation of the muscle is required for defecation.
  • Aids in maintaining urinary continence
Pubococcygeus
Iliococcygeus

Coccygeus

  • Branches of sacral nerves (S4–S5)

Urogenital diaphragm

Muscles of the urogenital diaphragm
Muscle Anatomy Innervation Function
Deep transverse perineal muscle
  • Runs from the ischial ramus towards the median plane to form a tendinous raphe with its counterpart muscle
  • Gives passage to the urethra (and the vagina in female individuals)
Urethral sphincter Internal urethral sphincter
  • Aids in maintaining urinary continence
  • Prevents retrograde ejaculation
External urethral sphincter In male individuals
  • Aids in maintaining urinary continence
In female individuals
  • Consists of three parts (from the inside out):
    • Sphincter muscle: muscle fibers encircling ∼ ⅔ of the proximal urethra
    • Compressor urethrae muscle
      • Continuous with the inferior fibers of the sphincter muscle
      • Contraction causes the urethra to collapse against the vagina.
    • Urethrovaginal muscle: broad band of muscle fibers surrounding both urethra and vagina
  • Aids in maintaining urinary continence
  • Contraction of the compressor urethrae causes the urethra to collapse against the vagina.

For more information on the muscles of the urinary tract, see “Overview of the urinary tract.”

Superficial perineal layer

Perineal region

Divisions of the perineal region

The perineal region can be divided by an imaginary line between the ischial tuberosities. This line forms two triangles within the perineal region, the urogenital triangle anteriorly and the anal triangle posteriorly. The contents of each triangle are listed below.

Arteries

Internal iliac artery

The blood supply of the pelvis is primarily derived from the internal iliac artery, which originates from the bifurcation of the common iliac artery. The internal iliac artery divides into the anterior trunk and the posterior trunk.

Other arteries

Veins

The veins follow the course of the arteries and are named accordingly, and they drain the same structures supplied by the arteries (e.g., internal iliac artery and internal iliac vein).

Nerves

Autonomic innervation

For additional information on the autonomic innervation of the pelvis, see “Nerves of the abdominal cavity” in “Abdominal cavity.”

Somatic innervation

For additional information on the lumbar and sacral plexus see ”Thigh, knee, and popliteal fossa” and for information on the innervation of the gluteal muscles, see “The gluteal region” below.

Lymphatics

The pelvic lymphatics course along the internal iliac vessels and drain into the lymph nodes listed below.

The gluteal region consists of a group of muscles that form the buttocks. These muscles arise from the pelvic girdle, are innervated by nerves that leave the pelvis through the greater sciatic foramen, and receive vascular supply from the superior and inferior gluteal arteries.

Overview of the gluteal muscles
Muscle group Muscle Origin Insertion Innervation

Function

Superficial gluteal muscles

Gluteus maximus
  • Iliotibial band, gluteal tuberosity of the femur
  • Inferior gluteal nerve: arises from L5, S1, S2
Gluteus medius
  • Greater trochanter
  • Superior gluteal nerve: arises from L4, L5, S1
Gluteus minimus
Tensor fasciae latae
Deep gluteal muscles Piriformis
  • Greater trochanter
Obturator internus
Superior gemellus

Inferior gemellus

Quadratus femoris
  • Intertrochanteric crest

All superficial gluteal muscles abduct and medially rotate the thigh. All deep gluteal muscles and the gluteus maximus laterally rotate the thigh.

The pelvis is derived from paraxial mesoderm and originates from two separate cartilaginous hemipelves. All three primary bone components are present around month 6–8. Important steps in the development of the pelvis, identified by weeks of embryonic development, are listed below.

Articulating bones

Ligaments of the hip joint

Overview of the ligaments of the hip joint
Description Function
Iliofemoral ligament
  • Reinforces the fibrous capsule anteriorly
  • Y-shaped ligament that runs from the anterior inferior iliac spine and the acetabular rim to the intertrochanteric line and the greater trochanter
  • Strongest ligament in the human body
  • Prevents excessive lateral rotation and hyperextension of the hip (in the standing position)
Ischiofemoral ligament
  • Reinforces the fibrous capsule posteriorly
  • Runs from the ischial region of the acetabulum to the neck of the femur medial to the greater trochanter
  • Limits medial rotation and extension of the thigh
Pubofemoral ligament
  • Runs from the pubic part of the acetabular rim and the superior pubic ramus to the lower part of the femoral neck
  • Reinforces the fibrous capsule inferiorly
Transverse acetabular ligament
  • Fibrous structure on the lower part of the acetabulum that converts the acetabular notch into a foramen
  • Allows passage of vessels and nerves into the joint space
Round ligament of the head of femur

Arterial supply of the hip joint

Movements of the hip joint

The muscles enabling movement of the hip joint can be divided into the gluteal muscles (see “The gluteal region” above) and the musculature of the thigh (see “Muscles of the thigh” in “Thigh, knee, and popliteal fossa”).

Kegel exercises involve the contraction of the entire levator ani. These exercises especially strengthen the pubococcygeus muscles, which can treat stress incontinence, urge incontinence, and pelvic organ prolapse and assists in ejaculation.