Pelvis and hip joint

Overview of the pelvis

General

Development of the pelvis

  • The pelvis starts to develop during the 3rd week of gestation.
  • Derived from paraxial mesoderm
  • Originates from two separate cartilaginous hemipelves
  • Events (by weeks) taking place in pelvic development
    • 6th week of development: The sacroiliac joint stats to develop.
    • 8th week of development: A fully developed pelvis is present in the embryo.
    • 9th week of development: The ilium starts to ossify via endochondral ossification.
    • 12th week of development: The anterior superior iliac spine (ASIS) and the pubis start to ossify.
    • 15th week of development: The ischium starts to ossify.

References:[1]

Bony pelvis

Hip bones

Bones Landmarks Anatomic features
Ilium
  • Contains:
    • Iliac fossa
    • Posterior iliac spine
    • Anterior superior iliac spine
    • Anterior inferior iliac spine
    • Greater sciatic notch
    • Gluteal lines
Ischium
  • Posterior and inferior part of the pelvic girdle
  • The body forms the inferoposterior part of the acetabulum
  • The ramus connects with the inferior pubic ramus
    • Forms the ischiopubic ramus
Pubis
  • Anteromedial part of the pelvic girdle
  • The superior ramus forms the anterior part of the acetabulum
  • The inferior ramus connects with the ramus of the ischium
    • Forms the ischiopubic ramus
  • Articulates on the midline to form the pubic symphysis

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

Pelvic inlet

Pelvic outlet

Joints of the pelvis

Joint Characteristics
Lumbosacral joint
  • Between the L5 vertebra and the sacral promontory
  • Stabilized by iliolumbar ligaments
Sacroiliac joint
  • Between the articular surfaces of the ilium and sacrum
  • Stabilized by the interosseous, anterior, and posterior sacroiliac ligaments
  • Synovial joint
  • Transmits weight from the vertebral column to the hip bones
  • Involved in sacroiliitis
Sacrococcygeal joint
  • Between the sacrum and coccyx
  • Stabilized by the lateral, anterior, and posterior sacrococcygeal ligaments
  • Cartilaginous joint
Pubic symphysis
  • Between pubic bones in the midline
  • Fibrocartilaginous or cartilaginous joint
  • Compensates shear forces while walking
  • Enables childbirth (by partially separating the pubic bones)
Hip joint
  • Ball-and-socket type of joint
  • Formed by the articulation of the femur and the acetabulum
  • See details in the section below

Pelvic diameters

  • See “Birth canal” below for more information on pelvic diameters.

Types of pelvises

  • See “Birth canal” below for more information on the types of pelvises.

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
Obturator foramen Round Triangular or oval
Subpubic angle Smaller Larger

Soft tissues of the pelvis

Urogenital diaphragm (triangular ligament)

Structure Anatomy
Deep transverse perineal muscle
  • Runs from the ischial rami towards the median plane, where it forms a tendinous raphe with its counterpart muscle
  • Innervated by the pudendal nerve
Urethral sphincter
Perineal membrane
  • Triangular-shaped membrane formed by the inferior border of the deep perineal pouch and the superior border of the superficial perineal pouch
  • Attached to the perineal body medially and the margins of the pubic and ischial rami laterally

Compressor urethrae muscle

  • Runs from the inferior pubic ramus bilaterally towards the median plane, where it wraps around the urethra (and vagina in females).

Muscle layers of the pelvis

Layer Muscle
Superficial perineal layer
  • Ischiocavernosus
  • Bulbocavernosus (bulbospongiosus in men)
  • Superficial transverse perineal
  • External anal sphincter
Deep urogenital diaphragm layer
Pelvic diaphragm

Ligaments of the pelvis

Ligament Anatomy and function
Anterior sacroiliac ligament
Posterior sacroiliac ligament
Sacrospinous ligament
Sacrotuberous ligament
  • Posterior attachment between the sacrum and the ischial tuberosity
  • Supports and immobilizes the sacrum during weight transfer from the vertebral column
Ligaments of the hip joint

Foramina of the pelvis

Foramen Anatomy Structures
Greater sciatic foramen
Lesser sciatic foramen
Obturator foramen
  • Formed by the ischium and pubis bones of the pelvis
  • Obturator foramen → obturator groove → obturator canal (delineated by the obturator membrane)
  • Boundaries
    • Anterior obturator tubercle (on the pubis)
    • Posterior obturator tubercle (on the ischium)
Pudendal canal
Vascular lacuna
  • Medial space in the upper thigh, below the inguinal ligament
  • Boundaries
    • Superior: inguinal ligament
    • Inferior: iliopectineal arch
    • Medial: lacunar ligament
    • Lateral: iliopectineal arch
Muscular lacuna
  • Lateral space in the upper thigh, below the inguinal ligament
  • Separated from the vascular lacuna by the iliopectineal line
  • Iliopsoas muscle
  • Lateral cutaneous nerve of the thigh
  • Femoral nerve

Pelvic cavity and spaces

Pelvic cavity

Pelvic spaces

Structure Anatomy
Rectovesical pouch (only in males)
  • Located between the upper posterior part of the urinary bladder and the upper and middle part of the rectum
  • Covered by a single layer of peritoneum
Rectouterine pouch of Douglas (only in females)
  • Located between the upper posterior part of the uterus and the upper and middle part of the rectum
Pararectal fossa
  • Connects at both sides with the rectovesical pouch in males and the rectouterine pouch in females
  • Located on both sides of the intraperitoneal portion of the rectum
  • Lateral boundaries
    • The uterosacral folds in females
    • The sacrogenital folds in males
Vesicouterine pouch (only in females)
  • Located between the posterior surface of the urinary bladder and the anterior surface of the uterus.
  • Bounded posterolaterally by the broad and round ligaments of the uterus
Rectovesical space (only in males)
  • Located posterior to the lower portion of the bladder and the prostate gland, inferior to the rectovesical pouch
  • Divided into three regions by the rectoprostatic fascia of Denonvillier (rectovesical)
    • Retrovesical region
    • Retroprostatic region
    • Prerectal region
Ischiorectal fossa (ischioanal fossa)
  • Located on both sides of the lower rectum and the anus
  • Triangular-shaped fossae
  • Boundaries
Retropubic space of Retzius
  • Located between the posterior surface of the pubis and the anterior surface of the bladder

Pelvic floor

Overview of the pelvic floor

  • A complex structure located in the opening of the pelvic outlet.
  • Funnel-shaped structure
  • Attached to the lesser pelvis
  • Separates the perineum from the pelvic cavity
  • Contains two openings
    • Rectal hiatus: allows passage of the anal canal. Located centrally.
    • Urogenital hiatus: allows passage of the urethra in both sexes and the vagina in females. Located anteriorly.
  • Contains the perineal body (central tendon of the perineum)
    • Fibromuscular structure
    • Between the anal and urogenital hiatus
  • Function
    • Supports abdominopelvic viscera (e.g., intestines, bladder, uterus, etc)
    • Resists and helps maintain increases in intraabdominal and intrapelvic pressure
    • Aids in fecal and urinary continence by contraction of muscle fibers
      • Relaxation of muscle fibers facilitate defecation and urination

Structures

Anatomy Function

Levator ani muscle

  • Runs from the body of the pubis, the ischial spine, and the arcus tendinous of the levator ani to the coccyx and the anococcygeal ligament
  • Innervated by anterior branches of sacral nerves (from S2S4 roots), and the perineal branch of the pudendal nerve
  • Formed by 3 muscles that maintain fecal continence
    • Puborectalis muscle: runs from the body of the pubic bones, around the lower rectum, and meets its counterpart muscle to form a sling around the lower rectum
    • Pubococcygeus muscle: runs from the body of the pubic bones and the anterior aspect of the tendinous arch, around the urogenital hiatus, to the coccyx and anococcygeal ligaments
    • Iliococcygeus muscle: runs from the ischial spines and the posterior aspect of the tendinous arch to the coccyx and anococcygeal ligaments

Coccygeus muscle

Fascial layers of the levator ani and coccygeus muscles also form part of the pelvic floor.

Birth canal

General

  • The female pelvis is larger and wider than the male pelvis.
  • The female pelvis is divided into:
    • True pelvis: below the linea terminalis (pelvic edge); comprises the bony canal: the ileum (superior-laterally), ischium (inferior-laterally), pubis (anteriorly), sacrum, and coccyx (posteriorly)
    • False pelvis: above the linea terminalis; consists of the abdominal wall (anteriorly), lumbar vertebrae (posteriorly), iliac fossae (laterally)
  • The birth canal is the passage, consisting of the mother's bony pelvis and soft tissues (i.e., uterus, cervix, vagina, vulva, and pelvic floor), through which a fetus passes during vaginal delivery. It is described in terms of:
    • Pelvic form
    • 3 pelvic regions
    • 4 pelvic planes
    • Soft tissue structures

Pelvic form, pelvic regions, and pelvic planes

Birth canal
Pelvic form
  • Gynecoid (typical female type): transverse oval inlet, wide sacrum, wide sacrosciatic notch, straight side walls, wide subpubic angle
  • Anthropoid (ape-like type): long anteroposterior diameters, short transverse diameters, wide sacrosciatic notch, narrow subpubic angle
  • Android (male type): triangular inlet, converging side walls, narrow sacrosciatic notch, narrow subpubic angle
  • Plateylpelloid (flat variation of gynecoid type): short anteroposterior diameters, long transverse diameters, narrow sacrosciatic notch, wide subpubic angle
Pelvic regions Pelvic inlet
  • Form: transverse ellipse
  • Boundaries: sacral promontory (posteriorly), linea terminalis (laterally), and symphysis pubis (anteriorly)
  • Diameters
    • True conjugate (tip of the sacral promontory to the upper border of the symphysis pubis) = ∼11 cm
    • Obstetric conjugate (tip of the sacral promontory to the most protruding point on the posterior surface of the symphysis pubis) = ∼10.5 cm
    • Transverse diameter (between the furthest two points on the iliopectineal lines) = ∼13 cm
    • Oblique diameters: right and left (sacroiliac joint to the each iliopectineal eminence) = ∼12 cm each, sacrocotyloid diameters (promontory of the sacrum to each iliopectineal eminence) = ∼ 9 cm
Pelvic cavity (mid-pelvis)
  • Form: round
  • Boundaries: plane of greatest and least pelvic diameter (roof and floor), sacrum (posteriorly), and symphysis pubis (anteriorly)
Pelvic outlet
  • Form: longitudinal oval
  • Boundaries: ischial spines (laterally), plane of least pelvic dimension (roof), pelvic outlet (floor), coccyx (posteriorly), and lower border of symphysis pubis (anteriorly)
  • Diameters: anteroposterior diameter = ∼13 cm, bituberous diameters = ∼11 cm, bispinous diameters = ∼10.5 cm
Pelvic planes Plane of the pelvic inlet
  • At the level of the pelvic brim boundaries and make an angle with the horizon (angle of pelvic inclination)
Plane of greatest pelvic dimension (mid-cavity)
  • At the level of the junction between the posterior surface of the symphysis pubis 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
Soft tissue structures
  • Inner portion
    • Lower uterine segment
    • Cervix
    • Vagina
    • Vulva
  • Outer portion: Pelvic floor

Vessels, nerves, and lymphatics of the pelvis

Arteries

Branches / Origin Area of supply
Internal iliac artery
  • Iliolumbar artery
  • Lateral sacral artery
  • Skin on the sacral region
  • Superior gluteal artery and inferior gluteal artery
  • Gluteal muscles
  • Perineum
  • Dome of the bladder (superior vesical artery), and the ductus deferens
  • Muscles of the thigh, and the head of the femur (via the acetabular branch)
  • Inferior vesical artery (vaginal artery in females)
  • Vaginal artery
  • Anterior and posterior wall of the vagina (can also arise from the uterine artery)
Medial sacral artery
  • Arises from the posterior wall of the aorta, proximal to the bifurcation
Superior rectal artery
Ovarian artery
  • Arises from the abdominal aorta
  • Crosses the proximal end of the external iliac artery

Veins

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

Nerves

For details on the sacral plexus see learning card on the lower extremities.

Structure Branches and area of supply
Autonomic nerves
Pudendal nerve (S2S4)

Lymphatics

Course along the internal iliac vessels and drain into the following lymph nodes:

Lymph nodes Area of drainage

Inferior mesenteric and aortic lymph nodes

  • Upper part of the rectum

Paraaortic lymph nodes

  • Ovaries
  • Fallopian tubes
  • Uterus (fundus)

Internal and external iliac lymph nodes

  • Uterus (body and cervix)
  • Bladder
  • Prostate and rectum (internal iliac nodes)

Hip joint

Overview

  • Definition: The hip joint (acetabulofemoral joint) is a joint between the head of the femur and the acetabulum of the pelvis.
  • Function: connects the axial skeleton to the lower extremities, and functions to support static (e.g., standing) and dynamic (e.g., walking, running) weight
  • Type of joint: ball-and-socket synovial joint
  • Movements: flexion and extension, lateral and medial rotation, abduction and adduction → the combination of these movements results in circumduction
  • Articular capsule: fibrous capsule that attaches to the margin of the acetabulum, the transverse acetabular ligament, and the neck of the femur.

For muscles of the hip joint and their blood supply and innervation, see the learning card on thigh, knee, and popliteal fossa.

Acetabulum

Ligaments of the hip joint

Anatomy Function
Iliofemoral ligament
  • Y-shaped ligament that runs from the anterior inferior iliac spine and the acetabular rim to the intertrochanteric line and the greater trochanter
  • Reinforces the fibrous capsule anteriorly
  • Strongest ligament in the human body
  • Prevents excessive lateral rotation and hyperextension of the hip (in the standing position)
Ischiofemoral ligament
  • Runs from the ischial region of the acetabulum to the neck of the femur medial to the greater trochanter
  • Reinforces the fibrous capsule anteriorly
  • 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
  • Limits abduction and extension
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
  • Originates within the acetabular fossa and attaches to the fovea capitis femoris (on the head of the femur)
  • Pathway for the foveolar artery to the head of the femur

The gluteal region

Muscle Origin Insertion Innervation

Function

Action occurs at the hip joint

Superficial gluteal muscles

Gluteus maximus
  • Gluteal tuberosity of the femur and iliotibial band
  • Inferior gluteal nerve
  • Lateral rotation and extension of the thigh
  • Forms the contour of the buttocks
Gluteus medius
  • Outer surface of the ilium, between the iliac crest, and anterior and posterior gluteal lines
  • Greater trochanter
  • Superior gluteal nerve
  • Medial rotation and abduction of the thigh
  • Stabilizes the pelvis
Gluteus minimus
  • Outer surface of the ilium, between the anterior and posterior gluteal lines
Tensor fascia latae
  • Iliac crest and anterior-superior iliac spine
  • Iliotibial band
  • Superior gluteal nerve
  • Medial rotation, flexion, and abduction of the thigh
Deep gluteal muscles Piriformis
  • Greater trochanter
  • Lateral rotation and abduction of the thigh
Obturator internus
  • Ischiopubic ramus and obturator membrane
Superior gemellus
  • Lateral rotation of the thigh
Inferior gemellus
  • Ischial tuberosity
Quadratus femoris
  • Ischial tuberosity
  • Intertrochanteric crest

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

Superior gluteal nerve palsy causes paralysis of the gluteus medius and minimus that results in a positive Trendelenburg sign.

Clinical significance

  • 1. Uhthoff HK. The Embryology of the Human Locomotor System. Berlin, Germany: Springer Science & Business Media; 2012.
  • Cunningham GR, Rosen RC. Overview of male sexual dysfunction. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/overview-of-male-sexual-dysfunction. Last updated May 11, 2016. Accessed February 23, 2017.
  • Jung J, Ahn HK, Huh Y. Clinical and functional anatomy of the urethral sphincter. Int Neurourol J. 2012; 16(3): pp. 102–6. doi: 10.5213/inj.2012.16.3.102.
  • Guccione AA, Wong R, Avers D. Geriatric Physical Therapy. Mosby; 2012.
last updated 11/25/2018
{{uncollapseSections(['OEcIDV0', 'lEcvDV0', 'NEc-DV0', 'mEcVwV0', 'MEcMwV0', '5Ccise0', '5EciwV0', 'nEc7wV0', 'sxctBe0', 'A9cRJe0'])}}