INTRODUCTION TO THE BONY PELVIS
©The University of Sydney
MODULE 1 – PELVIS AND LOWER LIMB ANATOMY
INTRO. TO THE BONY PELVIS
(WEEK 1)
COMMONWEALTH OF AUSTRALIA
Copyright Regulation
WARNING
This material has been reproduced and communicated to you
by or on behalf of the University of Sydney pursuant to Part
VB of the Copyright Act 1968 (the Act)
The material in this communication may be subject to copyright
under the Act. Any further reproduction or communication of
this material by you may be the subject of copyright
protection under the Act.
Do not remove this notice
BONES AND BONY MARKINGS OF THE PELVIS
Identify and delineate the ilium,
ischium and pubis on an adult hip
bone (BIOS1169 learning objective 1.3)
The adult hip (coxal) bone is an irregular
bone. It comprises three separate bones
in a child and younger teenager – the
ilium (flat blade) superiorly, the pubis
anteriorly and the ischium posteroinferiorly. These 3 bones fuse within the
socket of the hip joint (the acetabulum)
between the ages of 13 and 14 in females
and 15 and 16 in males.
© doctorlib.info/medical/anatomy/12.html
Orientate the bony pelvis (BIOS1169 learning objective 1.5)
The bony pelvis in an adult human is formed by the two hip bones articulating with each
other anteriorly and with the sacrum (S) (lowest part of the spine) posteriorly. A small
coccyx (Co) (‘tail bone’) also articulates with the sacrum inferiorly.
1
INTRODUCTION TO THE BONY PELVIS
©The University of Sydney
S
PSIS
ASIS
Co
PT
© Bass W.M. Human Osteology 1971 page 162
Three (3) bony markings need to be palpated to orientate the bony pelvis as well as to
assess the normality of your client’s pelvic posture. These bony markings are the
anterior superior iliac spine (ASIS) and pubic tubercle (PT) anteriorly PLUS the
posterior superior iliac spine (PSIS) posteriorly. Medical radiologists orientate the
pelvis by lining up the 2 x ASISs and 2 x pubic tubercles on the same coronal plane.
Other health professionals eg. physiotherapists, palpate the ASISs and PSISs then
check if they are lying on the same horizontal plane. Most people stand with their ASISs
lower than their PSISs.
Optional learning activity
Stand sideways to (for a lateral view) or facing (for an anterior view) a full length mirror.
Place the tips of your index fingers on the relevant bone markings needed to orientate in
each anatomical plane. Assess your own 3D pelvic posture using the criteria in the table.
[Reference: pages 656-657 in Magee, D.J. (2014) on Library website]
Anatomical
plane
sagittal
(lateral view)
‘Neutral’ pelvic posture
ASISs level with (on same
horizontal plane as) or lower (say
up to 10°) than PSISs
coronal/frontal
(anterior view)
R) ASIS level with (on same
horizontal plane as) L) ASIS
horizontal/
transverse
(superior view
(look down))
R) ASIS neither anterior nor
posterior to L) ASIS
My pelvic posture
(Circle one option)
‘neutral’ OR
anteriorly tilted (ASISs lower)
OR
posterior tilted (PSISs lower)
‘neutral’ OR
dropped on the R) OR
dropped on the L)
‘neutral’ OR
R) ASIS anterior to L) ASIS OR
R) ASIS posterior to L) ASIS
Now repeat the exercise with only one shoe on (on your right foot). This simulates a
longer “leg” on the right and shorter “leg” on the left. The pelvis will adjust its 3D posture
to compensate for this unequal leg length.
2
INTRODUCTION TO THE BONY PELVIS
©The University of Sydney
Identify gender differences in the bony pelvis & relate these differences
to differences in pelvic function (BIOS1169 learning objective 1.15)
The adult female pelvis is wider, shallower and lighter than an equivalent-in-size adult
male pelvis. The true pelvis itself (between the pelvic inlet and the pelvic outlet) as well
as the pelvic outlet also have different shapes in males and females. Some of the bony
markings are distinctly different. Most of the differences in male and female pelves relate
to child-bearing.
NOTE: The pelvic brim or inlet (i.e. the superior border of the true pelvis) shows less
distinction between the sexes than anatomy textbooks do indicate.
Activity: Identify the bone markings numbered 1 to 4 & complete the table below.
1
superior view of male pelvis
2
3
superior view of female pelvis
© Bass W.M. Human Osteology 1971 page 162
4
https://allthingsaafs.com/tag/ventral-arc/
No.
1
2
3
4
Bony marking
iliac crest
sacral promontory
ischial spine
obturator foramen
Appearance in males
3
Appearance in females
INTRODUCTION TO THE BONY PELVIS
©The University of Sydney
JOINTS WITHIN THE PELVIS (INTRINSIC PELVIC JOINTS)
Identify, classify and describe the movements available at the sacro-iliac
joints, pubic symphysis and sacrococcygeal joint (BIOS1169 learning objective 1.6)
R) SIJ
L) SIJ
SCocc jt
PS
th
© Rohen J.W. et al (2011) Color Atlas of Anatomy 7 edition Page 434
There are 4 joints within the bony pelvis – 2 sacroiliac joints (SIJs) between the sacrum
and the ilia of the left and right hip bones, 1 pubic symphysis (PS) between the pubic
bones of the left and right hip bones and 1 sacrococcygeal (SCocc) joint between the
sacrum and coccyx. These 4 joints are the intrinsic joints of the pelvis. Normally, motion
at all 4 joints is very restricted.
In a young adult, the SIJs are classified as partly synovial (their anterior parts) and
partly fibrous (their posterior parts). The PS and SCocc joints are classified as
fibrocartilaginous joints because they each contain a fibrocartilaginous disc.
Fibrocartilaginous joints are unpaired and located in the midline of the body.
Identify and describe the articular surfaces of the sacroiliac joints (SIJ)
(BIOS1169 learning objective 1.7)
The synovial part of each SIJ is the part between the two (2) twisted and ear-shaped
auricular surfaces on the lateral sides of the sacrum and the two (2) ilia. The
roughness of these surfaces varies with age and gender (rougher, more ridged &
grooved in makes). The fibrous part of each SIJ comprises a mass of very strong
ligaments that span between the lateral sacral crest and the iliac tuberosity.
lateral sacral crest
auricular surface
of hip bone (ilium)
auricular surface
of sacrum
posterolateral view of sacrum
iliac tuberosity
medial view of right hip bone
© Mediclip Human Anatomy 1, 2 & 3 Williams & Wilkins A Waverley Group 1996
4
INTRODUCTION TO THE BONY PELVIS
©The University of Sydney
Identify and describe the articular surfaces of the pubic symphysis (PS)
(BIOS1169 learning objective 1.7)
The oval-shaped symphyseal surfaces of each pubis are the
articular surfaces for the fibrocartilaginous PS. The roughness
of these surfaces varies with gender and age. They are wider
apart in females because of the wider inter-pubic disc in
females.
© emedicine.medscape.com
Describe motion at the PS (BIOS1169 learning objective
1.12). Shifting body weight from one lower limb to the other
produces minute translations in both a vertical and an AP
direction (shearing) as well as tiny rotations (mainly about a
vertical axis) (torsions) in the pubic symphysis (PS).
Identify and deduce one function of its articular disc (BIOS1169 learning objective
1.13) The inter-pubic disc resists any compression forces applied to the two hip bones
anteriorly. A wider disc permits increased motion at the PS. During childbirth, the PS
increases in width (goes under tension).
SACROILIAC JOINT MOTIONS: NUTATION & COUNTER-NUTATION
Define, demonstrate and state the range of sacral nutation and counternutation (BIOS1169 learning objective 1.8)
© Palastanga N. et al (2012) Anatomy and Human Movement 6th ed Fig. 3.57 page 281
Nutation is derived from the French word ‘nutare’ meaning to nod. Sacral nutation is
mainly an anterior rotation of the sacrum at each sacroiliac joint (SIJ) in the sagittal
plane about a transverse axis. During nutation, the base of the sacrum moves anteroinferiorly on the ilia of the hip bones (See B above). [NOTE: Sacral nutation is not an
anterior tilt (rotation) of the whole bony pelvis]. Sacral counter-nutation is mainly a
posterior rotation of the sacrum at each SIJ. During counter-nutation the base of the
sacrum moves posterosuperiorly on the ilia of the hip bones (See A above). [NOTE:
Sacral counter-nutation is not a posterior tilt (rotation) of the whole bony pelvis].
In a normal SIJ, sacral nutation and counter-nutation are tiny motions (less than 3°).
During childbirth, sacral nutation and counter-nutation increase in range to
accommodate the baby’s head as it passes through the birth canal.
5
INTRODUCTION TO THE BONY PELVIS
©The University of Sydney
LIGAMENTS OF THE SACROILIAC JOINT
Identify, state the attachments and deduce one (1) primary function of
each of the major ligaments associated with the sacroiliac joint (BIOS1169
learning objective 1.9)
4
1
2
2
3
© Rohen J.W. et al (2011) Color Atlas of Anatomy 7th edition Page 448
1
2
Pelvic
ligament
sacroiliac
ligaments
Proximal
attachment
margins of auricular
surfaces of sacrum +
lateral sacral crest
sacrospinous
ligament
edges of lower
sacrum & upper
coccyx
posterior border of
ilium bet. PSIS &
PIIS
transverse process
of L5
3
sacrotuberous
ligament
4
iliolumbar
ligament
Distal
attachment
margins of
auricular surface
of ilium + iliac
tuberosity
ischial
spine
ischial tuberosity
iliac crest
6
© The University of Sydney
Function(s)
prevent all but
<3° sacral nutation &
<3mm anterior shear of
sacrum
as above
(attachment site for a pelvic
floor muscle)
as above +
attachment site for 2 hip
muscles
as above +
limits tension of a SIJ