Overview of the pelvis

General

The pelvis (pelvic girdle) is the ring-like structure of the axial skeleton that connects the vertebral column with the lower extremities (e.g., femur).
The bony pelvis surrounds the pelvic cavity.
The pelvic cavity allows passage of gastrointestinal and urogenital structures into the pelvis.
The pelvis is largely immobile (unlike the pectoral girdle), which provides stability and proper transfer of weight from the vertebral column to the lower extremities, especially in the upright position.
The pelvis is composed of the following bones:
- The hip bones (os coxae): Ilium, ischium, and pubis
- Sacrum
- Coccyx
In addition, the bony pelvis is divided by the pelvic brim into:
- The pelvis major (false pelvis)
- The pelvis minor (true pelvis)

Development of the pelvis

The pelvis starts to develop during the 3^rd week of gestation.
Derived from paraxial mesoderm
Originates from two separate cartilaginous hemipelves
Events (by weeks) taking place in pelvic development
- 6^th week of development: The sacroiliac joint stats to develop.
- 8^th week of development: A fully developed pelvis is present in the embryo.
- 9^th week of development: The ilium starts to ossify via endochondral ossification.
- 12^th week of development: The anterior superior iliac spine (ASIS) and the pubis start to ossify.
- 15^th 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	Lateral part of the pelvic girdle The body of the ilium connects with the ischium and pubis Forms the superior part of the acetabulum The ala of the ilium forms the iliac crest
Ischium	Contains: Lesser sciatic notch Ischial spine Ischial tuberosity Posterior aspect of the obturator foramen	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	Pubic symphysis Anterior aspect of the obturator foramen	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

Location: superior rim of the pelvic cavity (upper pelvic aperture)
Boundaries
- Anterior: pectineal line, pubic crest, and the superior margin of the pubic symphysis
- Posterior: sacral promontory and anterior border of the sacral ala
- Lateral: arcuate line (iliopectineal line) of the ilium
Diameters: transverse, oblique, conjugate (anteroposterior), anatomical conjugate, diagonal, straight, median
Structures passing through the pelvic inlet: ureter, spermatic cord, round ligament of the uterus, suspensory ligament of the ovary, middle sacral vessels, gonadal vessels, iliolumbar vessels, lumbosacral trunk, sympathetic trunk, obturator nerve

Pelvic outlet

Location: lower pelvic aperture. It is narrower than the pelvic inlet.
Boundaries:
- Anterior: pubic symphysis, ischiopubic ramus, and the arcuate pubic ligament
- Posterior: sacrum and coccyx
- Lateral: ischial tuberosities and sacrotuberous ligaments
- Inferior: pelvic diaphragm and the urogenital diaphragm
Diameters: sagittal and intertuberous

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	Larger pelvic outlet Everted ischial tuberosities
Obturator foramen	Round	Triangular or oval
Subpubic angle	Smaller	Larger

Soft tissues of the pelvis

Urogenital diaphragm (triangular ligament)

Triangular muscular sheet located on the anterior part of the pelvic outlet, between the superior and inferior fascia (perineal membrane). It is external and inferior to the pelvic diaphragm.
Separates the upper pelvis from the deep perineal sac.

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	Consists of 2 muscles: internal urethral sphincter and external urethral sphincter Internal urethral sphincter: runs from the inferior bladder to the proximal urethra as an extension of the detrusor muscle Controlled by the autonomic nervous system (involuntary control) Prevents the release of urine External urethral sphincter Runs from the ischiopubic ramus towards the median plane, where it attaches with its counterpart muscle In males: surrounds the membranous urethra In females The inferior portion is attached to the vagina Forms part of the external sphincter muscle of the female urethra (urethrovaginal sphincter) Consists of 3 parts: Sphincter urethrae Urethrovaginal muscle: also surrounds the vagina Compressor urethrae: contraction causes the urethra to collapse against the vagina The external urethral sphincter is made of skeletal muscle (voluntary control) Innervated by the deep perineal branch of the pudendal nerve
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	Deep transverse perineal muscle Urethral sphincter Perineal membrane Compressor urethrae muscle
Pelvic diaphragm	Levator ani Coccygeus Piriformis Arcus tendinous of levator ani Arcus tendinous fasciae pelvis Obturator internus

Ligaments of the pelvis

Ligament	Anatomy and function
Anterior sacroiliac ligament	Anterior attachment between the ilium and the sacrum Supports the sacroiliac joint
Posterior sacroiliac ligament	Posterior attachment between the ilium and the sacrum Supports the sacroiliac joint
Sacrospinous ligament	Posterior attachment between the sacrum and the ischial spine Supports and immobilizes the sacrum during weight transfer from the vertebral column
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	See Ligaments of the hip joint.

Foramina of the pelvis

Foramen	Anatomy	Structures
Greater sciatic foramen	Formed by the sacrospinous and sacrotuberous ligaments Boundaries Inferior: sacrospinous ligament and the ischial spine Superior: anterior sacroiliac ligament Anterolateral: greater sciatic notch of the ilium Posteromedial: sacrotuberous ligament Piriformis muscle divides the greater sciatic foramen into suprapiriform and infrapiriform foramina.	Structures in the suprapiriform foramen Superior gluteal vessels and nerve Structures in the infrapiriform foramen Pudendal nerve Internal pudendal vessels Sciatic nerve Inferior gluteal vessels and nerve Nerve to the obturator internus muscle Nerve to the quadratus femoris muscle Posterior femoral cutaneous nerve
Lesser sciatic foramen	Formed by the sacrospinous and sacrotuberous ligaments Boundaries Superior: sacrospinous ligament and the ischial spine Anterior: ischial tuberosity Posterior: sacrotuberous ligament	Pudendal nerve Internal pudendal vessels Tendon of the obturator internus muscle Nerve to the obturator internus muscle
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)	Obturator artery, vein, and nerve
Pudendal canal	Formed by the fascia of the obturator internus muscle	Internal pudendal artery, veins, and pudendal nerve
Vascular lacuna	Medial space in the upper thigh, inferior to the inguinal ligament Boundaries Superior: inguinal ligament Inferior: iliopectineal arch Medial: lacunar ligament Lateral: iliopectineal arch	Femoral nerve (and the femoral branch of the genitofemoral nerve) Femoral artery Femoral vein Cloquet's node and other lymph nodes
Muscular lacuna	Lateral space in the upper thigh, inferior to the inguinal ligament Separated from the vascular lacuna by the iliopectineal line	Iliopsoas muscle Lateral cutaneous nerve of the thigh Femoral nerve

References:^[2]

Pelvic cavity and spaces

Pelvic cavity

The pelvic cavity is the space located within the pelvic girdle.
The superior opening is formed by the pelvic inlet, whereas the inferior opening is formed by the pelvic outlet.
The pelvic outlet is bounded by the pelvic floor, which functions to maintain pelvic organs in place. The division between the pelvic inlet and outlet is demarcated by the pelvic brim.
The pelvic cavity contains parts of the gastrointestinal tract (e.g., colon and rectum), urogenital tract (e.g., ureters, bladder, uterus), major blood vessels (e.g., iliac arteries and their branches), and nerves (e.g., pudendal nerve). In addition, the pelvic cavity contains muscles that attach to the spine and the lower limbs (e.g., psoas and iliacus muscles)

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 Superior: obturator internus muscle Inferior: ischial tuberosity Lateral: levator ani muscle
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
- Above: pelvic cavity
- Below: perineum
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 S2–S4 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	Supports and raises the pelvic floor The anterior fibers contain the levator prostate (in males), or pubovaginalis muscle (in females) Kegel exercises involve the contraction of the entire levator ani. Strengthening the pubococcygeus muscles is an effective measure against urinary incontinence.
Coccygeus muscle	Runs from the ischial spine and the sacrospinous ligament to the lower sacrum and the coccyx Innervated by branches of sacral nerves (S4–S5)	Supports and raises the pelvic floor
Fascial layers of the levator ani and coccygeus muscles also form part of the pelvic floor.

References:^[3]

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 2^nd and 3^rd 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		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	Iliac branch: supplies the ilium and the iliacus muscle Lumbar branch: supplies the quadratus lumborum muscle and the psoas major muscle
	Lateral sacral artery	Skin on the sacral region
	Superior gluteal artery and inferior gluteal artery Superior: above the piriformis muscle Inferior: below the piriformis muscle	Gluteal muscles
	Internal pudendal artery	Perineum
	Umbilical artery	Dome of the bladder (superior vesical artery), and the ductus deferens
	Obturator artery	Muscles of the thigh, and the head of the femur (via the acetabular branch)
	Inferior vesical artery (vaginal artery in females)	Fundus of the bladder, lower part of the ureter, prostate gland, seminal vesicles, and ductus deferens
	Vaginal artery	Anterior and posterior wall of the vagina (can also arise from the uterine artery)
	Middle rectal artery	Lower rectum, upper anal canal, prostate gland, seminal vesicles, and the ureter
	Uterine artery (artery of the ductus deferens in males)	Superior branch: supplies the body and fundus of the uterus Vaginal branch: supplies the cervix of the uterus and the vagina Anastomoses with the ovarian artery
Medial sacral artery	Arises from the posterior wall of the aorta, proximal to the bifurcation	Coccyx, lumbar vertebrae, sacrum
Superior rectal artery	Continuation of the inferior mesenteric artery (IMA)	Proximal rectum, superior to the pectinate line
Ovarian artery	Arises from the abdominal aorta Crosses the proximal end of the external iliac artery	Ovary through the suspensory ligament of the ovary

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

Superior hypogastric plexus
Hypogastric nerve
Inferior hypogastric plexus (pelvic plexus)
Sacral splanchnic nerves
Pelvic splanchnic nerves (from S2–S4)
- Carry parasympathetic fibers
- Form part of the pelvic plexus
- Innervate the descending and sigmoid colon, and organs in the pelvis and perineum (e.g., sexual organs)

Pudendal nerve (S2–S4)

Provides motor innervation to external urethral sphincter, external anal sphincter, levator ani, bulbospongiosus and the ischiocavernosus
Sensation to the perineum, penis/clitoris, posterior scrotum/labia, and the anal canal
- Reflex erection: afferent pudendal nerve → activates reflex arc to parasympathetic fibers in S2-4 roots (sacral erection center)
Sympathetic fibers to the penis/clitoris; responsible for male ejaculation
Injury (e.g., pelvic trauma or surgery) can cause urinary and fecal incontinence.
Used for pudendal nerve block during childbirth or during surgical procedures involving the perineum
- The ischial spine is used as a landmark for injection

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)

References:^[4]

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

Cup-like structure on the lateral side of the bony pelvis that articulates with the round femoral head
Covered by the acetabular labrum
- Ring of cartilage that provides an articular surface for the femoral head
Stabilized by capsular ligaments
Surrounded by the fibrous capsule
- Attaches to the margin of the acetabulum and to the transverse acetabular ligament
- Attaches to the neck of the femur
  - Anterior: intertrochanteric line (anterior) and the greater trochanter
  - Posterior: intertrochanteric crest
- Encloses the femoral head and the femoral neck
Receives blood supply from:
- Medial femoral circumflex artery
- Lateral femoral circumflex artery
- Obturator arteries
- Superior and inferior gluteal arteries
Innervated by:
- Femoral nerve
- Sciatic nerve
- Obturator nerve
- Superior gluteal nerve

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

The gluteal region consists of a group of muscles that form the buttocks
Gluteal 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.

	Muscle	Origin	Insertion	Innervation	Function Action occurs at the hip joint
Superficial gluteal muscles	Gluteus maximus	Sacrum, coccyx, ilium, and sacrotuberous ligament	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	Greater trochanter	Superior gluteal nerve
	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	Anterior surface of the sacrum and sacrotuberous ligament	Greater trochanter	Nerve to piriformis	Lateral rotation and abduction of the thigh
	Obturator internus	Ischiopubic ramus and obturator membrane		Nerve to obturator internus	Lateral rotation and abduction of the thigh
	Superior gemellus	Ischial spine		Nerve to obturator internus	Lateral rotation of the thigh
	Inferior gemellus	Ischial tuberosity		Nerve to quadratus femoris
	Quadratus femoris	Ischial tuberosity	Intertrochanteric crest	Nerve to quadratus femoris

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

Sacroiliitis (associated with e.g., ankylosing spondylitis, inflammatory bowel disease)
Uterine prolapse
Obturator hernia
Femoral hernia
Hip dislocation
Hip replacement
Coxarthrosis
Trendelenburg sign