Enhance your knowledge with our comprehensive guide and curated study materials.
The pelvic walls are formed by bones, muscles, and fascia that create a strong yet flexible basin supporting the pelvic viscera and transmitting neurovascular structures between the trunk and lower limb.
They are divided into:
Posterior wall – formed mainly by the sacrum and piriformis muscle.
Lateral walls – formed by the hip bone (ischium and part of ilium), obturator internus muscle, and obturator membrane.
Anterior wall – formed by the bodies of the pubic bones, pubic symphysis, and associated fascia.
Inferior wall (pelvic floor) – formed by the levator ani and coccygeus muscles, collectively known as the pelvic diaphragm.
These walls not only support pelvic organs like the bladder, uterus, and rectum, but also provide passage for important vessels and nerves that enter or leave the pelvis.
The main blood supply of the pelvis is derived from the internal iliac artery, a terminal branch of the common iliac artery, which arises from the abdominal aorta at the level of the L4 vertebra.
The pelvic veins, lymphatics, and nerves accompany these arteries in close relation to the pelvic viscera and muscles.
The internal iliac artery is the principal artery of the pelvis, supplying the pelvic walls, pelvic viscera, perineum, and parts of the gluteal and medial thigh regions.
It represents the major branch that ensures both somatic and visceral circulation in the pelvis.
The internal iliac artery arises from the common iliac artery opposite the lumbosacral disc (between L5 and S1).
It descends posteromedially into the pelvic cavity in front of the sacroiliac joint.
It usually measures 3–4 cm in length.
At the upper margin of the greater sciatic foramen, it divides into:
Anterior division → supplies viscera and muscles of the perineum and medial thigh.
Posterior division → supplies parietal branches to the pelvic wall and gluteal region.
Anteriorly:
In males → Ureter, vas deferens, and peritoneum of rectovesical pouch.
In females → Ureter and peritoneum of rectouterine pouch.
Posteriorly:
Internal iliac vein, lumbosacral trunk, and piriformis muscle.
Medially:
Pelvic viscera (rectum, bladder, uterus, vagina).
Laterally:
Obturator internus muscle and parietal pelvic fascia.
In males – six branches:
Superior vesical artery – supplies upper part of urinary bladder; gives artery to ductus deferens.
Obturator artery – runs along obturator fascia, passes through obturator foramen; gives iliac, vesical, and pubic branches (anastomoses with inferior epigastric).
Middle rectal artery – small; supplies mainly prostate and seminal vesicles, little to rectum.
Inferior vesical artery – to trigone of bladder, prostate, seminal vesicles, and lower ureter.
Inferior gluteal artery – largest branch; passes below piriformis to gluteal region; supplies buttock, back of thigh, and gives vesical branches.
Internal pudendal artery – terminal branch; supplies perineum and external genitalia, giving inferior rectal, perineal, bulb, urethral, deep and dorsal arteries
Volume 2, BD Chaurasia’s Human …
.In females – seven branches:
Inferior vesical artery is replaced by vaginal artery, which supplies vagina, bulb of vestibule, base of bladder, and nearby rectum.
An additional uterine artery supplies cervix, uterus, vagina, and uterine tube; crosses ureter 2 cm lateral to cervix
Volume 2, BD Chaurasia’s Human …
.Iliolumbar artery – ascends in front of sacroiliac joint, divides into:
Lumbar branch – to psoas, quadratus lumborum, erector spinae, and cauda equina.
Iliac branch – to iliacus and iliac fossa; participates in anastomosis around anterior superior iliac spine.
Lateral sacral arteries (two) – descend on sacral nerves; enter anterior sacral foramina to supply contents of sacral canal; exit posteriorly to supply muscles and skin of back of sacrum.
Superior gluteal artery – passes above piriformis through greater sciatic foramen; supplies gluteus maximus and nearby muscles; participates in anastomoses around anterior superior iliac spine and greater trochanter
Volume 2, BD Chaurasia’s Human …
.Lies posteromedial to the internal iliac artery.
Joins external iliac vein to form common iliac vein at pelvic brim.
Tributaries correspond to the arterial branches, except that iliolumbar vein drains directly into common iliac vein.
Tributaries include:
Parietal veins: superior gluteal (largest), inferior gluteal, internal pudendal, obturator, lateral sacral veins.
Visceral veins: from rectal, prostatic, vesical, uterine, and vaginal venous plexuses
Volume 2, BD Chaurasia’s Human …
.Pelvic lymphatics drain into three main groups of nodes located along the corresponding vessels:
Common iliac nodes (4–6) – receive lymph from internal and external iliac nodes; efferents go to lateral aortic nodes.
External iliac nodes (8–10) – receive lymph from inguinal nodes, infraumbilical abdominal wall, prostate, bladder base, cervix, and vagina.
Inferior epigastric and circumflex iliac nodes are part of this group.
Internal iliac nodes – receive lymph from all pelvic viscera, deep perineum, and gluteal region; efferents drain to common iliac nodes.
Sacral and obturator nodes are outlying members of this group
Volume 2, BD Chaurasia’s Human …
.To study the pelvic vessels:
Remove the pelvic viscera carefully from the cavity.
Trace the internal iliac artery and its anterior and posterior divisions, following each branch to its destination in the viscera or pelvic walls.
Remove the venous plexuses (rectal, vesical, prostatic, uterine, and vaginal) to visualize the arteries clearly.
Identify and clean the hypogastric plexus lying near the bifurcation of the common iliac artery
The pelvic nerves include:
Lumbosacral plexus
Coccygeal plexus
Pelvic autonomic nerves
Volume 2, BD Chaurasia’s Human …
.Formation:
Formed by the lumbosacral trunk (L4–L5) and ventral rami of S1–S3 with part of S4.
The lumbosacral trunk is made by the descending branch of L4 and entire ventral ramus of L5, crossing the pelvic brim in front of the sacroiliac joint to join S1
Volume 2, BD Chaurasia’s Human …
.Relations:
Lies in front of piriformis and behind internal iliac vessels and ureter.
Superior gluteal vessels separate L4–L5 and S1; inferior gluteal vessels separate S1 and S2
Volume 2, BD Chaurasia’s Human …
.Before forming the plexus, ventral rami give off:
Nerves to piriformis (S1, S2)
Nerves to levator ani, coccygeus, and sphincter ani externus (S4)
Pelvic splanchnic nerves (S2, S3, S4)
Volume 2, BD Chaurasia’s Human …
The plexus gives rise mainly to:
Sciatic nerve – for locomotion
Pudendal nerve – for perineal and reproductive functions
Volume 2, BD Chaurasia’s Human …
Superior gluteal nerve (L4, L5, S1): To gluteus medius, minimus, and tensor fasciae latae.
Inferior gluteal nerve (L5, S1, S2): To gluteus maximus.
Nerve to piriformis (S1, S2).
Perforating cutaneous nerve (S2, S3).
Volume 2, BD Chaurasia’s Human …
Nerve to quadratus femoris (L4, L5, S1).
Nerve to obturator internus (L5, S1, S2).
Pudendal nerve (S2, S3, S4): To sphincter ani externus and muscles of urogenital triangle.
Muscular branches (S4): To levator ani, coccygeus, and sphincter ani externus.
Pelvic splanchnic nerves (S2–S4): Parasympathetic fibers to pelvic viscera
Volume 2, BD Chaurasia’s Human …
.Formed by descending branch of S4, S5, and coccygeal nerve.
Lies on pelvic surface of coccygeus.
Gives rise to anococcygeal nerves, which pierce sacrotuberous ligament to supply skin over coccyx and anus
Volume 2, BD Chaurasia’s Human …
.Lumbosacral trunk (L4–L5) and S1 nerve may be compressed or inflamed in sacroiliac joint disease, causing pain radiating below the knee.
L4 root → pain in medial leg and sole; S1 root → pain in lateral foot.
Injury to pudendal nerve causes perineal sensory loss and sphincter weakness (fecal or urinary incontinence)
The pelvic part of the sympathetic chain runs downward and slightly medially over the sacral bodies, along the medial margins of the anterior sacral foramina.
Both chains unite in front of the coccyx to form a small ganglion impar.
Each chain contains four sacral ganglia on either side and one median ganglion impar.
Branches of the pelvic sympathetic chain include:
Grey rami communicantes to all sacral and coccygeal ventral rami.
Branches to the inferior hypogastric plexus from the upper ganglia.
Branches to the median sacral artery from the lower ganglia.
Branches to the rectum from the lower ganglia.
Filaments to the glomus coccygeum from the ganglion impar
Volume 2, BD Chaurasia’s Human …
.The inferior hypogastric plexus (pelvic plexus) lies on either side of the rectum and pelvic viscera.
It is formed by:
Hypogastric nerve from the superior hypogastric plexus.
Branches from the upper sacral sympathetic ganglia.
Pelvic splanchnic nerves (S2–S4).
Branches of the inferior hypogastric plexus include:
Rectal plexus
Vesical plexus
Prostatic plexus (in males)
Uterovaginal plexus (in females)
Volume 2, BD Chaurasia’s Human …
.These nerves represent the sacral outflow of the parasympathetic system.
They arise as fine filaments from the ventral rami of S2, S3, and S4 and join the inferior hypogastric plexus to supply the pelvic viscera.
Their functions include:
Motor to smooth muscles of bladder and rectum.
Vasodilator to erectile tissue.
Secretomotor to glands of pelvic organs.
Some parasympathetic fibers ascend through the hypogastric nerve to the superior hypogastric plexus and further to the inferior mesenteric plexus, thus reaching parts of the hindgut.
Others ascend independently to supply the descending colon and sigmoid colon, reflecting their hindgut derivation
Volume 2, BD Chaurasia’s Human …
.
Expose the lumbosacral trunk and ventral rami of sacral nerves (S1–S5).
Lift the sacral plexus forward to identify the sciatic and pudendal nerves.
Locate nerves emerging from the dorsal surface of the plexus (e.g., superior and inferior gluteal nerves).
Trace branches from the pelvic surface—nerves to quadratus femoris and obturator internus.
Identify the pelvic sympathetic trunks on the sacrum and trace them to the ganglion impar on the coccyx.
Follow the grey rami communicantes from the sacral ganglia to sacral nerves.
Finally, locate the inferior hypogastric plexus around the internal iliac vessels
The pelvic fascia covers the muscles of the lateral pelvic wall and is thick and strong.
It is closely adherent to the pelvic cavity walls and is attached along a line from the iliopectineal line to the inferior border of the pubic bone.
The fascia over the obturator internus forms the obturator fascia, which shows a linear thickening (tendinous arch) for the origin of the levator ani.
Below this arch, it relates to the pudendal canal.
The fascia covering the piriformis is thin; sacral nerves lie outside the fascia, while gluteal vessels lie inside it and pierce it when exiting the pelvis
Volume 2, BD Chaurasia’s Human …
.The fascia covers both surfaces of the pelvic diaphragm, forming superior and inferior layers (the latter called anal fascia).
It is loosely arranged between the peritoneum and pelvic floor, forming potential spaces for the distension of bladder, rectum, uterus, and vagina.
Because of its loose areolar nature, infections may spread rapidly within it.
At certain places, the fascia condenses to form fibromuscular ligaments that support pelvic viscera — e.g., puboprostatic, pubovesical, uterosacral, and rectovesical ligaments
Volume 2, BD Chaurasia’s Human …
.Surrounds the extraperitoneal parts of the pelvic viscera.
Loose and cellular around distensible organs (bladder, rectum, vagina) but dense around non-distensible ones (prostate).
Attached along a line from the back of the pubis to the ischial spine, forming a continuity between parietal and visceral fascia
Volume 2, BD Chaurasia’s Human …
.Pelvic muscles are divided into two groups:
Piriformis and Obturator Internus – short lateral rotators of the hip joint.
Levator Ani and Coccygeus – form the pelvic diaphragm, separating the pelvic cavity from the perineum
Volume 2, BD Chaurasia’s Human …
.The levator ani is a broad, thin, sheet-like muscle forming the greater part of the pelvic diaphragm. It consists of three main parts:
Origin: Medial part of the pelvic surface of the pubic body.
Insertion:
Anterior fibers surround the prostate (levator prostatae) in males or vagina (sphincter urethrovaginalis) in females and insert into the perineal body.
Middle fibers form the puborectalis, looping around the anorectal junction, maintaining fecal continence.
Posterior fibers arise from the anterior half of the white line and insert into the anococcygeal ligament and tip of coccyx
Volume 2, BD Chaurasia’s Human …
.Origin: Posterior half of the tendinous arch (white line) on obturator fascia and ischial spine.
Insertion: Into the anococcygeal ligament and last two pieces of the coccyx.
Thinner than the pubococcygeus, it forms the posterolateral part of the pelvic diaphragm
Volume 2, BD Chaurasia’s Human
Triangular muscle forming the posterior part of the pelvic diaphragm.
Origin: Pelvic surface of ischial spine and sacrospinous ligament.
Insertion: Side of coccyx and fifth sacral vertebra.
Levator ani:
Branch from fourth sacral nerve (S4).
Branch from inferior rectal nerve.
Coccygeus: Branch from fourth and fifth sacral nerves
Volume 2, BD Chaurasia’s Human …
.Support pelvic viscera and fix perineal body.
Close posterior pelvic outlet with coccygeus.
Resist intra-abdominal pressure during coughing, sneezing, defecation, and parturition.
Puborectalis maintains the anorectal angle, preventing premature fecal descent.
Coccygeus draws coccyx forward after defecation or childbirth
The levator ani is a broad, sheet-like muscle forming the major portion of the pelvic diaphragm, which supports the pelvic viscera and maintains continence. It is divided into three parts — pubococcygeus, iliococcygeus, and ischiococcygeus (coccygeus)
Volume 2, BD Chaurasia’s Human …
.
Origin: Medial part of the pelvic surface of the pubic body.
Insertion:
Anterior fibers form levator prostatae (in males) or sphincter urethrovaginalis (in females), inserting into the perineal body.
Middle fibers form the puborectalis, looping around the anorectal junction to maintain fecal continence.
Posterior fibers arise from the anterior half of the tendinous arch (white line) and attach to the anococcygeal ligament and tip of coccyx
Volume 2, BD Chaurasia’s Human …
.Origin: Posterior half of the tendinous arch and the ischial spine.
Insertion: Anococcygeal ligament and sides of the last two coccygeal vertebrae.
This part is thinner and forms the posterolateral portion of the pelvic diaphragm
Volume 2, BD Chaurasia’s Human …
.Shape: Triangular; partly muscular, partly tendinous.
Origin: Pelvic surface of ischial spine and sacrospinous ligament.
Insertion: Side of coccyx and fifth sacral vertebra
Volume 2, BD Chaurasia’s Human …
.Levator ani:
Branch from fourth sacral nerve (S4).
Branch from inferior rectal nerve.
Coccygeus: Branch from fourth and fifth sacral nerves
Volume 2, BD Chaurasia’s Human …
.Close the posterior part of the pelvic outlet.
Support and elevate pelvic viscera; fix the perineal body.
Resist intra-abdominal pressure during coughing, sneezing, and defecation, maintaining urinary and fecal continence.
Puborectalis sling pulls the anorectal junction forward to prevent premature fecal passage.
Coccygeus draws the coccyx forward after it is displaced backward in defecation or childbirth
Volume 2, BD Chaurasia’s Human …
.Superior (pelvic) surface: Covered with pelvic fascia; related to bladder, prostate, rectum, and peritoneum.
Inferior (perineal) surface: Covered with anal fascia; forms the medial boundary of ischioanal fossa.
Anterior borders: Separated by a triangular space for urethra and vagina.
Posterior border: Free; lies against the anterior margin of coccygeus
Volume 2, BD Chaurasia’s Human …
.Identify piriformis on the sacrum and trace it to the greater sciatic foramen.
Expose the ischial spine, tracing origins of coccygeus and levator ani.
Follow the tendinous arch over obturator internus to the pubic body.
Note union of right and left levator ani at perineal body, anal canal, and anococcygeal ligament.
Detach levator ani from obturator fascia to visualize pudendal canal and its contents
Volume 2, BD Chaurasia’s Human …
.Weakness or damage to levator ani (especially pubococcygeus) during childbirth causes pelvic organ prolapse.
Pudendal nerve injury leads to incontinence.
Chronic strain may cause levator ani syndrome, presenting as dull pelvic or rectal pain.
Puborectalis dysfunction can cause anorectal angle abnormalities, resulting in constipation.
The pelvis contains several key articulations that contribute to stability, weight transmission, and limited movement during locomotion and childbirth. The principal joints include the lumbosacral, sacroiliac, and sacrococcygeal joints
Volume 2, BD Chaurasia’s Human …
.
The joint between L5 and the sacrum is similar to other intervertebral joints, having a thick intervertebral disc (the thickest in the vertebral column), which is slightly wedge-shaped—thicker anteriorly.
Stability is reinforced by:
Widely spaced articular processes.
Iliolumbar ligament, which extends from the transverse process of L5 to the iliac crest and ala of sacrum, forming the lumbosacral ligament.
The lumbosacral (sacrovertebral) angle measures about 120°, opening backward.
Variations include sacralisation of L5, lumbarisation of S1, spina bifida, and spondylolisthesis
Volume 2, BD Chaurasia’s Human …
.The sacrococcygeal joint is a secondary cartilaginous joint between the apex of the sacrum and the base of the coccyx.
United by:
A thin intervertebral disc.
Ventral sacrococcygeal ligament (analogous to anterior longitudinal ligament).
Deep dorsal sacrococcygeal ligament (analogous to posterior longitudinal ligament).
Superficial dorsal sacrococcygeal ligament, completing the lower end of the sacral canal.
Lateral sacrococcygeal ligament, forming the foramen for the fifth sacral nerve.
Intercornual ligament, connecting cornua of sacrum and coccyx.
In old age, this joint ossifies, while in some people it may be synovial and mobile.
Intercoccygeal joints exist in youth but fuse by age 30
Volume 2, BD Chaurasia’s Human …
.Synovial joint (plane type), allowing limited gliding movement.
Between auricular surface of sacrum (fibrocartilage) and auricular surface of ilium (hyaline cartilage).
Fibrous capsule: encloses the joint and is lined by synovial membrane.
Ventral sacroiliac ligament: thickening of the anterior and inferior capsule, attached to preauricular sulcus.
Interosseous sacroiliac ligament: strongest; connects rough non-articular areas of sacrum and ilium, forming the chief bond of union.
Dorsal sacroiliac ligament: covers the interosseous ligament and has two parts —
Short posterior sacroiliac ligament: from ilium to first two sacral tubercles.
Long posterior sacroiliac ligament: from posterior superior iliac spine to third and fourth sacral tubercles, blending laterally with sacrotuberous ligament.
Accessory (vertebropelvic) ligaments:
Iliolumbar ligament: from L5 transverse process to iliac crest, prevents forward slip of L5.
Sacrotuberous ligament: from posterior inferior iliac spine and sacrum to ischial tuberosity.
Sacrospinous ligament: from lateral sacrum to ischial spine, forming the greater and lesser sciatic foramina
Volume 2, BD Chaurasia’s Human …
.Remove thoracolumbar fascia and posterior muscles.
Identify iliolumbar and dorsal sacroiliac ligaments.
Cut through dorsal sacroiliac ligament to expose the interosseous ligament, then open the joint posteriorly.
Define and cut ventral sacroiliac ligament to open the joint anteriorly
Volume 2, BD Chaurasia’s Human …
.Pregnancy: Pelvic joints and ligaments become relaxed, increasing movement and reducing stability; may lead to sacroiliac strain that persists postpartum.
Subluxation can occur if the hip bones remain rotated after childbirth, causing low back pain.
Differentiation of pain:
Lumbosacral lesions → tenderness above the posterior superior iliac spine (iliolumbar region).
Sacroiliac lesions → tenderness inferomedial to the PSIS (posterior sacroiliac region).
Interosseous sacroiliac ligament is considered the strongest ligament in the body
The pelvis is primarily designed for stability rather than mobility, as it transmits body weight from the vertebral column to the lower limbs. Stability is maintained through:
Interlocking articular surfaces of the sacroiliac joint, which resist shear forces.
Strong interosseous and dorsal sacroiliac ligaments, the chief stabilizers of the joint.
Vertebropelvic ligaments — iliolumbar, sacrotuberous, and sacrospinous — which limit movement and enhance stability.
Partial synostosis of the sacroiliac joint with advancing age, which further reduces motion and increases rigidity
Volume 2, BD Chaurasia’s Human …
.The sacroiliac joint receives blood from branches of the posterior division of the internal iliac artery, including:
Iliolumbar artery
Lateral sacral artery
Superior gluteal artery
Volume 2, BD Chaurasia’s Human …
Innervation is provided by:
Superior gluteal nerve
Ventral rami and lateral branches of dorsal rami of the first and second sacral nerves (S1–S2)
Volume 2, BD Chaurasia’s Human …
The sacroiliac joint allows minimal anteroposterior rotatory movement (tilting) around a transverse axis located 5–10 cm below the sacral promontory.
These slight movements absorb shock during jumping or heavy loading.
During pregnancy, the range of movement temporarily increases due to hormonal ligament relaxation, aiding fetal delivery
Volume 2, BD Chaurasia’s Human …
.This is a secondary cartilaginous joint between the bodies of right and left pubic bones.
Each articular surface is covered by hyaline cartilage, with a fibrocartilaginous disc in between.
The joint is reinforced by ligamentous fibers, thickest inferiorly to form the arcuate pubic ligament and anteriorly forming the anterior pubic ligament.
It allows slight movement to absorb shocks, and mobility increases during pregnancy under hormonal influence
Volume 2, BD Chaurasia’s Human …
.The pelvis acts as a weight-transmitting structure, transferring the trunk’s load to the lower limbs through the alae of the sacrum and the acetabular region.
The weight at the lumbosacral joint divides into two components:
a. One drives the sacrum downward and backward between the ilia — resisted by pubic symphysis ligaments.
b. The other pushes the upper sacrum downward and forward — resisted by the middle sacroiliac joint, where the posterior wedge-shaped surface interlocks with the ilium.
Rotation of sacrum: Body weight causes the anterior sacral segment to tilt downward and posterior segment upward.
Dorsal and interosseous sacroiliac ligaments prevent anterior tilt.
Sacrotuberous and sacrospinous ligaments prevent posterior tilt.
Sacroiliac, iliolumbar, and pubic ligaments resist lateral separation of hip bones
Volume 2, BD Chaurasia’s Human …
.Identify the posterior sacroiliac, sacrotuberous, and sacrospinous ligaments.
Trace the iliolumbar ligament from the L5 transverse process to the iliac crest.
Dissect anteriorly to reveal interosseous and ventral sacroiliac ligaments.
Note pubic symphysis anteriorly and lumbosacral junction superiorly.
Pregnancy: Hormonal relaxation increases pelvic joint mobility, causing sacroiliac strain and low back pain.
Pelvic instability may persist postpartum due to ligament laxity.
Subluxation or rotation of hip bones can cause chronic pelvic discomfort.
Pubic symphysis diastasis may occur after difficult labor.
The sacroiliac interosseous ligament is among the strongest in the human body, crucial for pelvic stability
Uterine artery is an additional branch of the internal iliac artery, exclusive to females.
The ventral ramus of L4 contributes to both lumbar and sacral plexuses and is termed nervus furcalis.
Nerves forming the sacral plexus lie outside the parietal layer of pelvic fascia, while pelvic blood vessels lie inside it.
The interosseous sacroiliac ligament is the strongest ligament in the body, providing chief stability to the pelvic ring.
Free anastomoses between the superior rectal vein (portal system) and the middle and inferior rectal veins (systemic circulation) explain metastatic spread to the liver from genital organ cancers.
The sensory supply of ovary and fallopian tube arises from T10–T12 spinal segments
Volume 2, BD Chaurasia’s Human …
.Case:
An elderly person was struck and run over by a speeding vehicle.
Questions & Answers:
Which bones are likely to be fractured?
The pubic bone on one side is typically fractured, and the sacroiliac joint on the opposite side may be dislocated.
What structures form the pelvic ring?
The pelvic ring is formed by the pubic rami, acetabulum, ilium, ischium, sacrum, and pubic symphysis—forming a continuous bony and ligamentous loop.
Which viscera are likely to be injured?
The urinary bladder, urethra, rectum, and reproductive organs (e.g., prostate or uterus) are vulnerable due to their close relation to the pelvic floor and pubic symphysis.
What types of joints are the pubic symphysis and sacroiliac joints?
Pubic symphysis: Secondary cartilaginous joint (amphiarthrosis).
Sacroiliac joint: Synovial plane joint, reinforced by strong ligaments
1. Pelvic Joint Pathology in Pregnancy
During pregnancy, relaxin hormone softens the ligaments of the sacroiliac and pubic symphysis joints. This increases joint mobility and widens the pelvic outlet for childbirth. However, the relaxation also leads to sacroiliac strain, pelvic girdle pain, and sometimes subluxation of pubic symphysis, causing difficulty in walking or standing
Volume 2, BD Chaurasia’s Human …
.
2. Distinguishing Sacroiliac from Lumbosacral Lesions
In lumbosacral disease, tenderness appears above the posterior superior iliac spine (iliolumbar region).
In sacroiliac disease, tenderness is felt inferomedial to the same point (posterior sacroiliac ligament region).
Movements: lumbosacral lesions restrict all spinal movements, whereas sacroiliac lesions cause pain mainly during forward bending, when tension on hamstrings rotates the hip bones opposite to the sacrum
Volume 2, BD Chaurasia’s Human …
.3. Pelvic Ring Fracture (Run-over Injury)
A run-over accident may cause fracture of the pubic rami on one side and dislocation of the opposite sacroiliac joint. This disrupts the pelvic ring, which is formed by the pubic rami, acetabulum, ilium, ischium, sacrum, and pubic symphysis. Such injuries often involve bladder, urethra, rectum, or genital organs, demanding urgent management
Volume 2, BD Chaurasia’s Human …
.
4. Sacroiliac Joint Disorders
Chronic infection (tuberculosis) or ankylosing spondylitis can lead to fibrous or bony ankylosis of the sacroiliac joint, causing low back pain and stiffness. Radiographic evaluation shows erosion, sclerosis, or fusion of articular margins.
5. Degenerative Osteoarthritis of Pubic Symphysis
Common in elderly and postmenopausal women, degeneration of the fibrocartilaginous disc at the pubic symphysis produces pain during walking or rising from sitting, due to reduced shock absorption.
6. Pelvic Fracture and Urethral Injury (Males)
In males, a fracture of the pubic arch or dislocation of pubic symphysis may tear the membranous urethra, leading to extravasation of urine into the deep perineal space and scrotum.
7. Obstetric Implication of Sacral Curvature
Excessive forward curvature of the sacrum (sacral kyphosis) may narrow the pelvic inlet, causing obstructed labor, while a flat sacrum can reduce the pelvic outlet angle, complicating delivery.
8. Postpartum Sacroiliac Locking
After childbirth, if the pelvic ligaments re-tighten while the hip bones remain rotated, the sacroiliac joints may lock in a rotated position, causing chronic low backache and pelvic asymmetry
Volume 2, BD Chaurasia’s Human …
.
9. Referred Pain in Pelvic Disorders
Due to shared segmental innervation (L4–S2), diseases of pelvic viscera may refer pain to the sacroiliac region, buttock, or posterior thigh, often mimicking sciatica.
Q1. What are the main joints of the pelvis?
The pelvic joints include the lumbosacral joint, sacroiliac joints, sacrococcygeal and intercoccygeal joints, and the pubic symphysis
Volume 2, BD Chaurasia’s Human …
.
Q2. What type of joint is the sacroiliac joint?
It is a synovial plane joint, allowing minimal gliding movement. Stability is mainly ensured by strong ligaments and the interlocking articular surfaces.
Q3. What type of joint is the pubic symphysis?
A secondary cartilaginous joint (amphiarthrosis) between the bodies of the pubic bones united by a fibrocartilaginous disc.
Q4. Which ligaments strengthen the sacroiliac joint?
Interosseous sacroiliac ligament (strongest)
Ventral and dorsal sacroiliac ligaments
Iliolumbar, sacrotuberous, and sacrospinous ligaments (accessory stabilizers)
Q5. What are the main functions of the pelvic joints?
They transmit body weight from the vertebral column to the lower limbs, absorb shocks, and provide limited flexibility for childbirth and locomotion.
Q6. What maintains the stability of the pelvis?
Interlocking sacroiliac surfaces
Strong interosseous ligaments
Pubic symphysis integrity
Vertebropelvic ligament system (iliolumbar, sacrotuberous, sacrospinous)
Q7. Which ligament is considered the strongest in the body?
The interosseous sacroiliac ligament, lying between the sacrum and ilium, is the chief stabilizer of the pelvis.
Q8. What are the movements at the sacroiliac joint?
Only slight anteroposterior tilting of the sacrum (nutation and counternutation) occurs, helping absorb forces during posture changes or childbirth.
Q9. What happens to the pelvic joints during pregnancy?
Hormones like relaxin cause ligament relaxation, increasing joint mobility to facilitate childbirth but also predisposing to pelvic girdle pain.
Q10. What is the mechanism of weight transmission in the pelvis?
Body weight at the lumbosacral joint is transmitted through the sacrum to the ilia, then to the acetabula and femurs. The sacroiliac and pubic ligaments prevent displacement during this transfer.
Q11. How can pelvic injury lead to visceral damage?
Fractures of the pelvic ring or dislocation of the pubic symphysis can injure the urinary bladder, urethra, rectum, or reproductive organs, due to their close anatomic relations.
Q12. What is the clinical difference between lumbosacral and sacroiliac pain?
Lumbosacral lesions: Pain felt above the posterior superior iliac spine.
Sacroiliac lesions: Pain below or inferomedial to the same point, worsened on forward bending.
Q13. Why do vertebral or pelvic metastases commonly occur?
Because the valveless Batson’s venous plexus connects pelvic veins with the vertebral venous system, allowing retrograde spread of infection or malignancy.
Q14. What is the importance of the pubic symphysis during delivery?
Its fibrocartilaginous disc allows slight separation of the pubic bones, increasing the anteroposterior diameter of the pelvic outlet to aid childbirth.
Q15. What is the consequence of injury to the pelvic floor muscles or ligaments?
Damage or stretching (especially of the levator ani or perineal body) leads to uterine or vaginal prolapse, urinary incontinence, and chronic pelvic instability.
1. Which of the following joints is a secondary cartilaginous joint?
A. Sacroiliac joint
B. Lumbosacral joint
C. Pubic symphysis
D. Hip joint
Answer: C. Pubic symphysis
2. The sacroiliac joint is of which type?
A. Hinge joint
B. Plane synovial joint
C. Pivot joint
D. Condyloid joint
Answer: B. Plane synovial joint
3. The strongest ligament in the human body is the:
A. Sacrotuberous ligament
B. Interosseous sacroiliac ligament
C. Sacrospinous ligament
D. Iliolumbar ligament
Answer: B. Interosseous sacroiliac ligament
4. Which hormone causes relaxation of pelvic ligaments during pregnancy?
A. Progesterone
B. Relaxin
C. Estrogen
D. Oxytocin
Answer: B. Relaxin
5. Which ligament converts the greater sciatic notch into a foramen?
A. Sacrotuberous ligament
B. Sacrospinous ligament
C. Interosseous sacroiliac ligament
D. Iliolumbar ligament
Answer: B. Sacrospinous ligament
6. The lumbosacral joint between the fifth lumbar vertebra and the sacrum forms an angle called:
A. Sacrococcygeal angle
B. Lumbosacral angle
C. Pelvic tilt angle
D. Pubic angle
Answer: B. Lumbosacral angle
7. The pelvic ring is composed of all the following EXCEPT:
A. Pubic symphysis
B. Sacrum
C. Coccyx
D. Acetabulum
Answer: C. Coccyx
8. Which structure transmits weight from the vertebral column to the lower limbs?
A. Sacrococcygeal joint
B. Sacroiliac joint
C. Pubic symphysis
D. Ischiopubic ramus
Answer: B. Sacroiliac joint
9. In which joint is movement most limited in adults due to ossification with age?
A. Sacrococcygeal joint
B. Lumbosacral joint
C. Sacroiliac joint
D. Pubic symphysis
Answer: A. Sacrococcygeal joint
10. During parturition, the diameter of which part of the pelvis increases due to ligament relaxation?
A. Pelvic inlet
B. Pelvic outlet
C. Pelvic cavity
D. None of these
Answer: B. Pelvic outlet
11. The sacroiliac joint is stabilized by which of the following ligaments?
A. Interosseous sacroiliac ligament
B. Sacrospinous ligament
C. Sacrotuberous ligament
D. All of the above
Answer: D. All of the above
12. Which of the following is not a function of the pelvic joints?
A. Weight transmission
B. Locomotion
C. Speech
D. Shock absorption
Answer: C. Speech
13. Pain in sacroiliac disease is typically felt:
A. Over the sacral promontory
B. Inferomedial to the posterior superior iliac spine
C. Over the iliac crest
D. Over the pubic symphysis
Answer: B. Inferomedial to the posterior superior iliac spine
14. Which joint of the pelvis shows nutation and counternutation movements?
A. Pubic symphysis
B. Sacroiliac joint
C. Sacrococcygeal joint
D. Lumbosacral joint
Answer: B. Sacroiliac joint
15. Which of the following structures passes through the lesser sciatic foramen?
A. Piriformis muscle
B. Obturator internus tendon
C. Sciatic nerve
D. Superior gluteal artery
Answer: B. Obturator internus tendon
Q1. What are the main joints forming the pelvic ring?
The lumbosacral, sacroiliac, and pubic symphysis joints together form the pelvic ring, which transmits body weight to the lower limbs
Volume 2, BD Chaurasia’s Human …
.
Q2. What type of joint is the sacroiliac joint?
It is a synovial plane joint—its movements are minimal but crucial for stability and shock absorption.
Q3. What type of joint is the pubic symphysis?
A secondary cartilaginous joint (amphiarthrosis), united by a fibrocartilaginous disc.
Q4. Name the ligaments strengthening the sacroiliac joint.
Ventral and dorsal sacroiliac ligaments
Interosseous sacroiliac ligament (strongest)
Sacrotuberous and sacrospinous ligaments (accessory stabilizers)
Q5. Which ligament forms the greater and lesser sciatic foramina?
The sacrospinous ligament (with the sacrotuberous ligament).
Q6. What is the function of the interosseous sacroiliac ligament?
It is the chief bond of union between the sacrum and ilium, resisting separation and shear forces.
Q7. Which movements occur at the sacroiliac joint?
Small anteroposterior rotations (nutation and counternutation) of the sacrum relative to the ilium.
Q8. What happens to these joints during pregnancy?
The hormone relaxin softens pelvic ligaments, increasing mobility of the sacroiliac and pubic symphysis joints to facilitate childbirth.
Q9. What is the function of the pubic symphysis?
It acts as a shock absorber, allowing slight movement between the two pubic bones during walking and childbirth.
Q10. Which ligaments resist rotation of the sacrum?
Interosseous and dorsal sacroiliac ligaments resist forward tilt.
Sacrotuberous and sacrospinous ligaments resist backward tilt.
Q11. What forms the main weight-transmitting path in the pelvis?
From L5 vertebra → sacrum → ilium → acetabulum → femur.
Q12. What is the lumbosacral angle?
The angle between the long axis of L5 and the sacral base, normally about 120°, opening backward.
Q13. What are common variations of the lumbosacral region?
Sacralisation of L5
Lumbarisation of S1
Spina bifida
Spondylolisthesis
Q14. Which artery supplies the sacroiliac joint?
Branches of the superior gluteal, iliolumbar, and lateral sacral arteries.
Q15. Which nerves supply the sacroiliac joint?
Superior gluteal nerve
Ventral rami and dorsal branches of S1 and S2
Q16. What are the clinical implications of sacroiliac joint weakness?
Can lead to low back pain, sacroiliac strain, or pelvic instability, especially after childbirth.
Q17. What happens to the sacrococcygeal joint with age?
It often ossifies, reducing mobility.
Q18. What is the mechanism of pelvic stability?
Mutual wedging of the sacrum between the hip bones, secured by strong ligaments and the pubic symphysis.
Q19. Which structures can be injured in pelvic fractures?
The bladder, urethra, rectum, and reproductive organs, due to their proximity to the pelvic floor.
Q20. Why is the sacroiliac joint more stable than mobile?
Because it is primarily designed for weight transmission rather than movement; its rough interlocking surfaces and strong ligaments prevent displacement.
Get the full PDF version of this chapter.
Continue with Google