Pelvis and hip joint (Hip)

Summary

The bony pelvis is composed of the two hip bones, the sacrum, and the coccyx, which are firmly connected by the pubic symphysis (between the pubic bodies of the two hip bones), the sacrococcygeal symphysis (between the coccyx and the sacrum), and sacroiliac joints (between the ilium of the hip bones and the sacrum). Each hip bone consists of the ilium, ischium, and pubic bone. The pelvis connects the lower extremity to the trunk, protects abdominal and pelvic organs, and provides attachment to muscles and ligaments. The pelvic cavity is a space located within the pelvic girdle that contains parts of the gastrointestinal tract and urogenital tract. The pelvic joints and the organs are supported by muscles and ligaments (including the urogenital diaphragm). The pelvic cavity contains anatomical spaces, such as the rectouterine pouch (of Douglas) in women and the rectovesical pouch in men. The pelvic floor, which is composed of muscles and fascia, separates the pelvic cavity from the perineum. It has openings that allow for the passage of the rectum, vagina, and urethra. It furthermore helps maintain fecal and urinary continence and prevents pelvic organ prolapse. The female pelvis, which accommodates the birth canal, is larger and wider than the male. The hip joints (acetabulofemoral joint) are joints located between the head of the femur and the acetabulum of the pelvis that connect the trunk to the lower extremities. The hip joint supports dynamic and static body weight. The gluteal region consists of the gluteal muscles that form the buttocks. The gluteal muscles receive vascular supply from the superior and inferior gluteal arteries.

Overview of the pelvis

General

Development of the pelvis

References:[1]

Bony pelvis

Hip bones

Bones Landmarks Anatomic features
Ilium
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

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
Sacrococcygeal joint
Pubic symphysis
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” section for more information on pelvic diameters.

Types of pelvises

See “Birth canal” section 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
Deep urogenital diaphragm layer
Pelvic diaphragm

Ligaments of the pelvis

Ligament Anatomy and function
Anterior sacroiliac ligament
Posterior sacroiliac ligament
Sacrospinous ligament
Sacrotuberous ligament
Ligaments of the hip joint

Foramina of the pelvis

Foramen Anatomy Structures
Greater sciatic foramen
Lesser sciatic foramen
Obturator foramen
Pudendal canal
Vascular lacuna
Muscular lacuna

Trauma or strain of the piriformis muscle may cause entrapment of the sciatic nerve, leading to buttock pain and paresthesia in the distribution of the sciatic nerve (piriformis syndrome).

References:[2][3]

Pelvic cavity and spaces

Pelvic cavity

Pelvic spaces

Space Anatomy
Rectovesical pouch (only in males)
  • Peritoneal space formed by reflection of peritoneum over the posterior bladder and the anterior rectum
  • The lowest part of the peritoneal cavity in the upright position in males, where intraperitoneal fluid (e.g., ascites, blood, or pus) preferentially collects
Rectouterine pouch of Douglas (only in females)
  • Peritoneal space formed by reflection of the peritoneum over the uterus and posterior fornix of the vagina anteriorly and the rectum posteriorly
  • The lowest part of the peritoneal cavity in the upright position in females, where blood, pus, malignant cells, and endometrial implants preferentially collect
Pararectal fossa
Vesicouterine pouch (only in females)
  • Peritoneal space formed by reflection of the peritoneum over the fundus and body of the uterus posteriorly and posterosuperior surface of the bladder anteriorly
  • Bounded posterolaterally by the broad and round ligaments of the uterus
Rectovesical space (only in males)
Ischiorectal fossa (ischioanal fossa)
Retropubic space of Retzius

.

Pelvic floor

Overview of the pelvic floor

Muscles of the pelvic floor [4][5]

Anatomy Function

Levator ani

Coccygeus

  • Runs from the ischial spines to the sacrum and the coccyx, overlying the sacrospinous ligaments
  • Innervated by branches of sacral nerves (S4–S5)

Kegel exercises involve the contraction of the entire levator ani and can treat both stress and urge incontinence as well as pelvic organ prolapse.

References:[6]

Birth canal

General

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)
Plane of least pelvic dimension (obstetric outlet)
Plane of the anatomical outlet
Soft tissue structures

Vessels, nerves, and lymphatics of the pelvis

Arteries

Branches/origin Area of supply
Internal iliac artery
  • Skin on the sacral region
  • Gluteal muscles
  • Perineum
  • Muscles of the thigh, and the head of the femur (via the acetabular branch)

Median sacral artery

Superior rectal artery
Ovarian 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 thigh, knee, and popliteal fossa

Structure Branches and area of supply
Autonomic nerves
Pudendal nerve (S2–S4)

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

Paraaortic lymph nodes

Internal and external iliac lymph nodes

References:[7]

Hip joint

Overview

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
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
  • Pathway for the foveolar artery to the head of the femur

Movements of the hip joint

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
  • Lateral rotation and extension of the thigh
  • Abduction (upper fibers) and adduction (lower fibers) of the hip
  • Forms the contour of the buttocks
Gluteus medius
  • Greater trochanter
Gluteus minimus
Tensor fasciae latae
  • Iliotibial band
Deep gluteal muscles Piriformis
  • Greater trochanter
Obturator internus
  • Ischiopubic ramus and obturator membrane
Superior gemellus
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.
  • 2. 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.
  • 3. Hopayian K et al. The clinical features of the piriformis syndrome: a systematic review. European Spine Journal. 2010; 19(12): pp. 2095–2109. doi: 10.1007/s00586-010-1504-9.
  • 4. Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences; 2016.
  • 5. Drake R. Gray's Anatomy for Students. Elsevier; 2019.
  • 6. Guccione AA, Wong R, Avers D. Geriatric Physical Therapy. Mosby; 2012.
  • 7. 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.
last updated 07/09/2020
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