This document provides an overview of the major joints in the pelvic region, including the femoroacetabular joint, pubic symphysis, and sacroiliac joint. It describes the bones, blood supply, innervation, and main muscles involved in these joints. Specifically, it notes that the pelvis is comprised of the sacrum fusing with the two innominate bones, which form the acetabulum where the femur articulates to create the weight-bearing femoroacetabular joint. The pelvic region joints work together for stability during movement and to distribute weight from the upper body to the lower extremities.

1.
Lower
Extremity
Arthrology
Guide
Summer
2015
Derya
Anderson
Scott
Bentley
Bow
Decker
Ashley
Haight
Cynthia
Hobbs
Jennifer
Rogers
Jill
Stephenson
Andrew
Trevino
Table
18

2. 2
Arthrology
Guide:
Table
of
Contents
Introduction
to
the
Pelvic
Region………………………………………………………….………..3
Femoroacetabular
Joint………………………………………………………………………..…7
Pubic
Sympyhsis
………………………………………………………………………….............16
Sacroiliac
Joint…………………………………………………………………………………..….20
Introduction
to
the
Knee
Complex…………………………………………………………………25
Tibofemoral
Joint……………………………………………………………………………......…30
Patellofemoral
Joint………………………………………………………………….……...….…37
Introduction
to
the
Ankle
Joint………………………………………………………………………42
Proximal
Tibiofibular
Joint
…………………………………………………………...….……45
Distal
Tibiofibular
Joint
……………………………………………………………….………...47
Talocrural
Joint……………………………………………………………………………………...50
Subtalar
Joint………………………………………………………………………………………...56
Introduction
to
the
Foot
Complex………………………………………………………….………62
Transverse
Tarsal
Joints
………………………………………………………….…………….65
Distal
Intertarsal
Joints
………………………………………………………………………….73
Tarsometarsal
Joints……………………………………………………..……………………….79
Intermetarsal
Joints……………………………………………………………………………….84
Metatarsophalangeal
Joints…………………………………………………………………….87
Interphalangeal
Joints…………………………………………………………………………….93

3. 3
Introduction
to
the
Pelvic
Region
The
pelvic
region
contains
three
major
joints.
It
includes
the
femoroacetabular
joint
(hip
joint),
the
sacroiliac
joint
(SI),
and
the
pubic
symphysis.
These
three
joints
work
together
for
the
purpose
of
weight
bearing,
stability,
and
shock
absorption/weight
distribution.
The
joint’s
second
but
equally
important
purpose
is
to
allow
dynamic
movement
such
as
walking,
running,
and
jumping.
These
joints
have
to
be
able
to
work
together
to
provide
the
stability
required
so
dynamic
movements
can
occur
effectively
and
pain
free.
The
pelvis
is
comprised
of
the
sacrum
and
an
innominate
bone
on
each
side.
The
union
of
these
bones
creates
the
sacroiliac
joint
and
the
pubic
symphysis.
As
mentioned
above,
the
pelvis
serves
to
distribute
weight
from
the
upper
body
down
to
the
lower
extremities.
This
is
done
very
effectively
due
to
the
ring
that
is
created
from
the
joining
of
these
three
bones.
The
pelvis
is
also
important
due
to
the
many
muscle
attachment
sites
from
both
the
lower
extremity
and
the
trunk.
The
last
component
of
the
pelvic
region
includes
the
femur
bone.
The
head
of
the
femur
articulates
with
the
acetabulum
to
create
the
femoroacetabular
joint.
The
innominate
is
comprised
of
three
parts:
the
ilium,
the
ischium,
and
the
pubis.
These
three
components
of
the
innominate
come
together
to
form
the
acetabulum
(Figure
1).
It
is
at
this
joint
that
most
of
the
weight
bearing
occurs.
The
pelvic
region
receives
its
main
blood
supply
from
the
internal
and
external
iliac
arteries
which
ultimately
originate
from
the
split
of
the
abdominal
aorta.
The
internal
iliac
artery
supplies
blood
to
the
organs
of
the
pelvis
and
the
surrounding
muscles,
and
the
external
iliac
artery
travels
laterally
to
supply
blood
to
the
femoroacetabular
joint
and
the
lower
extremities.
The
pelvic
region
is
innervated
by
the
lumbosacral
plexus.
The
plexus
arises
from
the
ventral
root
of
T12-­‐S4
(Figure
2).
The
lumbar
portion
of
the
plexus
goes
to
innervate
the
anterior
and
lateral
aspect
of
the
pelvis
while
the
sacral
portion
innervates
the
posterior
and
lateral
aspect
of
the
pelvis.
Figure
1.
Bones
of
the
acetabulum
Figure
2.
Nervous
supply
of
pelvis

4. 4
Table
1.
Muscles
Acting
on
the
Pelvic
Joints
Muscle
Proximal
Attachment
Distal
Attachment
Segmental
Innervations
Peripheral
Innervations
Gluteus
max
Aponeurosis
of
the
erector
spinae,
sacrum,
sacrotuberous
ligament
&
posterior
gluteal
line
(innominate)
Greater
trochanter,
gluteal
tuberosity
of
the
femur
&
the
iliotibial
tract
L5-­‐S1-­‐2
Inferior
Gluteal
Nerve
Gluteus
medius
External
iliac
surface
Oblique
ridge
on
the
lateral
aspect
of
the
greater
trochanter;
gluteal
aponeurosis
L4-­‐5-­‐S1
Superior
Gluteal
Nerve
Gluteus
minimis
External
iliac
surface
and
margin
of
the
greater
sciatic
notch
Anterolateral
aspect
of
the
greater
trochanter
L4-­‐5-­‐S1
Superior
Gluteal
Nerve
Piriformis
Anterolateral
sacrum
&
posterior
inferior
iliac
spine
Upper
border
of
the
greater
trochanter
(L5)
S1-­‐2
Nerve
to
the
piriformis
Superior
gemellus
Xternal
surface
spine
of
ischium
via
obturator
internus
tendon
to
greater
trochanter
Greater
trochanter
L5-­‐S1-­‐S2
Sacral
Plexus
Obturator
internus
Anterolateral
wall
of
the
pelvis
&
obturator
membrane
Medial
surface
of
the
greater
trochanter
L5-­‐S1-­‐2
Nerve
to
the
obturator
internus
(from
sacral
plexus)
Obturator
externus
Rami
of
pubis
and
ischium;
external
surface
obturator
membrane
Trochanteric
fossa
L3-­‐4
Obturator
Nerve
Inferior
gemellus
Proximal
ischial
tuberosity
via
obturator
internus
tendon
Greater
trochanter
L4-­‐5-­‐S1
(S2)
Sacral
Plexus

5. 5
Quadratus
femoris
Ischial
tuberosity
Quadrate
tubercle
of
the
femur
L4-­‐5-­‐S1,
(S2)
Nerve
to
quadratus
femoris
from
sacral
plexus
Hamstring
(Semimembra
n-­‐osus,
Semitendinos
us,
Biceps
femoris)
SM:
ischial
tuberosity
ST:
ischial
tuberosity
BF:
ischial
tuberosity
&
sacrotuberous
lig.
(long
head)
;
lateral
lip
of
linea
aspera
&
lateral
supracondylar
line
(short
head)
SM:
posterior
aspect
of
the
medial
tibial
condyle
ST:
proximal,
medial
tibia
BF:
the
lateral
side
of
fibular
head
SM:
L4-­‐5-­S1-­‐2
ST:
L4-­‐5-­S1-­2
BF:
L5-­‐S1-­2-­‐3
to
long
head;
L5-­S1-­2
to
short
head
SM:
tibial
division
of
the
sciatic
nerve
ST:
tibial
division
of
the
sciatic
nerve
BF:
tibial
branch
of
sciatic
(long
head)
&
fibular
branch
of
sciatic
nerve
(short
head)
Adductor
magnus
Inferior
pubic
ramus,
ischial
ramus
&
tuberosity
Gluteal
tuberosity,
linea
aspera,
medial
supracondylar
ridge
&
adductor
tubercle
of
the
femur
L2-­‐3-­‐4
&
L4-­‐
5-­‐S1
Obturator
nerve
(adductor
region)
&
tibial
division
of
the
sciatic
nerve
Adductor
longus
Pubic
crest
Medial
lip
of
linea
aspera
L2,
L3,
L4
Obturator
nerve
Adductor
brevis
Inferior
pubic
ramus
Distal
2/3
pectineal
line
and
medial
lip
linea
aspera
L2,
L3,
L4
Obturator
nerve
Adductor
minimus
Inferior
Rami
Linea
Aspera
of
the
femur
L2,
L3,
L4
Obturator
and
Tibial
nerve
TFL
Anterior
superior
iliac
spine
&
external
lip
iliac
crest
Iliotibial
tract
L4,
L4,
S1
Superior
gluteal
nerve
Quadriceps
(Vastus
Lateralis,
VL:
intertrochanteric
line,
greater
trochanter,
gluteal
tuberosity
&
linea
VL:
base
&
lateral
border
of
the
patella
VM:
medial
border
L2,
L3,
L4
Femoral
nerve

6. 6
Vastus
Medialis,
Vastus
intermedius)
aspera
VM:
intertrochanteric
line,
spiral
line,
linea
aspera
&
medial
supracondylar
line
VI:
anterior
aspect
of
the
proximal
2/3rds
of
the
femoral
shaft
of
the
patella
VI:
lateral
border
of
the
patella
Rectus
femoris
Anterior
inferior
Iliac
Spine
Base
of
the
patella
L2,
L3,
L4
Femoral
nerve
Sartorius
Anterior
Superior
Iliac
Spine
Medial
aspect
of
the
proximal
tibia
L2-­‐L3
(L4)
Femoral
nerve
Pectineus
Superior
pubic
ramus
Femur
between
the
lesser
trochanter
&
linea
aspera
(pectineal
line)
L2-­‐3-­‐4
Femoral
nerve
&
obturator
nerve
Gracilis
Body
of
the
pubis
&
inferior
pubic
ramus
Medial
surface
of
tibia,
distal
to
condyle,
proximal
to
insertion
of
semitendinosus,
lateral
to
insertion
of
sartorius
L2-­‐3-­‐4
Obturator
nerve
Iliopsoas
·
Iliacus
·
Psoas
major
Iliacus:
iliac
fossa,
iliac
crest,
sacral
ala
&
SI
ligaments
Psoas
Major:
anterior
transverse
processes,
vertebral
bodies
&
discs
Iliacus:
femur
just
distal
to
lesser
trochanter
Psoas:
lesser
trochanter
Iliacus:
(L1)
L2-­‐3-­‐4
Psoas:
L1-­‐2-­‐3-­‐
4
Iliacus:
Lumbar
plexus

7. 7
Femoroacetabular
Joint
The
femoroacetabular
joint
is
the
articulation
of
the
acetabulum
and
the
head
of
the
femur.
The
main
purpose
of
the
joint
is
to
bear
the
weight
of
the
trunk
and
upper
extremity
in
static
positions
as
well
as
with
dynamic
movements.
The
joint
must
be
stable
enough
to
bear
the
weight
of
the
body
as
well
as
mobile
enough
to
allow
dynamic
movement
to
occur.
Stability
is
achieved
through
the
many
ligaments
and
muscles
surrounding
the
joint.
Mobility
is
achieved
through
the
nature
of
the
joint
being
a
ball
and
socket
joint.
Neurovascular
Supply
(Figure
3)
The
hip
joint
receives
its
arterial
supply
from
the
medial
circumflex
artery
and
the
lateral
circumflex
artery.
These
two
arteries
arise
from
the
profunda
femoris
artery
and
supply
the
head
and
neck
of
the
femur.
Specifically,
branches
off
the
medial
circumflex
artery
called
retinacular
arteries
are
the
most
abundant
and
its
main
supplier.
An
artery
call
the
‘artery
to
the
head
of
the
femur’
is
located
inside
the
ligamentum
teres.
It
is
a
branch
from
the
obturator
artery
and
supplies
the
head
of
the
femur
as
well
but
very
minimally.
Moore
mentions
that
a
nerve
innervating
any
muscles
that
crosses
a
joint
also
innervates
the
joint
itself.
This
is
known
as
Hilton’s
Law.
Taking
this
into
account,
the
hip
flexors
are
innervated
by
the
femoral
nerve,
lateral
rotators
by
the
obturator
nerve
and
the
nerve
to
quadratus
femoris,
and
abductors
by
superior
gluteal
nerve.
These
nerves
all
originate
from
the
ventral
rami
of
the
lumbosacral
plexus.
Tissue
Layers
from
Superficial
to
Deep
• Integumentary
o epidermis
o dermis
o hypodermis
• Neurovascular
o Nervous
Tissue
! Femoral
nerve
! Obturator
nerve
! Sciatic
nerve
! Superior
gluteal
nerve
! Inferior
gluteal
nerve
o Vascular
Tissue
! Femoral
artery
! Medial
femoral
circumflex
artery
Figure
3.
Blood
supply
to
the
proximal
femur

8. 8
! Superior
and
inferior
gluteal
(minor
contributions)
! Lateral
femoral
circumflex
artery
! Artery
of
ligamentum
teres
• Muscle
o Hip
extensor
muscles
o Hip
adductor
muscles
o Hip
flexor
muscles
• Ligaments
o Iliofemoral
ligament
o Ischiofemoral
ligament
o Pubofemoral
ligament
• Joint
Capsule/Tissue
o Fibrous
capsule
o Synovial
membrane
o Synovial
fluid
• Articular
cartilage
• Labrum
• Bone
o Head
of
the
femur
o Acetabulum
Biomechanics
of
the
Femoroacetabular
Joint
The
hip
joint
is
a
classic
ball
and
socket
joint.
A
ball
and
socket
joint
is
known
to
allow
the
greatest
amount
of
movement.
Even
so,
the
number
one
priority
of
the
hip
joint
is
stability
followed
by
movement.
The
hip
receives
its
stability
from
the
large
amount
of
muscles
and
ligaments
that
surround
it.
Mobility
comes
from
the
three
degrees
of
freedom
of
the
joint.
Before
discussing
the
movements
in
each
plane,
one
must
look
at
the
kinematics
of
the
hip.
When
the
femur
is
moving
in
a
stable
pelvis,
it
is
described
as
femur-­‐
on-­‐pelvis.
When
the
pelvis
is
moving
on
a
stable
femur,
it
is
known
as
pelvis-­‐on-­‐femur.
Different
motions
and
movements
occur
depending
on
which
scenario
one
considers.
Below
is
a
description
of
movements
in
each
plane:
Pelvis-­‐on-­‐Femur:
Sagittal
plane:
Posterior
and
anterior
tilt
Transverse
Plane:
Internal
and
external
rotation
of
the
hip
Frontal
Plane:
Abduction
and
adduction
of
the
hip
Femur-­‐on-­‐Pelvis
Sagittal
Plane:
Flexion
and
extension
Transverse
Plane:
Internal/external
rotation
of
femur
Frontal
Plane:
Abduction
and
adduction
of
hip
Joint
Configuration
of
the
Femoroacetabular
Joint
As
mentioned
above,
the
hip
joint
is
a
ball
and
socket
joint.
A
ball
and
socket
joint
is
a
synovial
joint
that
allows
the
most
amount
of
freedom
as
it
has
movements
in
all
three
planes.
It
consists
of
a
convex
surface
moving
on
a
concave
surface
or
vice
versa.
The
table
below
summarizes
the
osteokinematics,
arthrokinematics,
and
planes
the
hip
joint
functions
in.
The
movements
are
described
in
open-­‐chain
position.

9. 9
Table
2.
Movements
of
the
Femoroacetabular
Joint
Plane
Osteokinematics
Arthrokinematics
Sagittal
Flexion
(120°)
Roll
anteriorly,
glide
posteriorly
Sagittal
Extension
(20°)
Rolls
posteriorly
and
glides
anteriorly
Transverse
Internal
Rotation
(45°)
Rolls
medially
and
glides
laterally
Transverse
External
Rotation
(45°)
Rolls
laterally
and
glides
medially
Frontal
Abduction
(45°)
Rolls
laterally
and
glides
medially
Frontal
Adduction
(30°)
Rolls
medially
and
glides
laterally
The
degrees
of
motion
are
according
to
the
AAOS
guideline
The
roll
allows
for
the
joint
to
move
into
the
proper
position
while
the
glide
prevents
the
head
of
the
femur
from
falling
out
of
the
acetabulum.
The
table
below
lists
the
primary
and
secondary
movers
of
specific
motions.
Table
3.
Joint
Motions
of
the
Femoroacetabular
Joint
Joint
Motion
Primary
Movers
Secondary
Movers
Flexion
iliopsoas,
sartorius,
TFL,
Rectus
femoris,
Adductor
Longus,
pectineus
Adductor
Brevis,
Gracilis,
Gluteus
Minimus
(anterior
fibers)
Extension
Gluteus
Maximus,
Biceps
Femoris
(long
head),
Semitendinosus,
Semimembranosus,
Adductor
Magnus
(posterior
head)
Gluteus
Medius
(posterior
fibers),
Adductor
Magnus
(anterior
head)
Abduction
Gluteus
Medius,
Gluteus
Minimus,
TFL
Piriformis,
Sartorius
Adduction
Pectineus,
Adductor
Longus,
Gracilis,
Adductor
Brevis,
Adductor
Magnus
Biceps
Femoris
(long
head),
Gluteus
Maximus
(lower
fibers),
Quadratus
Femoris

10. 10
Internal
Rotation
N/A
Gluteus
Minimus
(anterior
fibers),
Gluteus
Medius
(anterior
fibers),
TFL,
Adductor
Longus,
Adductor
Brevis,
Pectineus
External
Rotation
Gluteus
Maximus,
Piriformis,
Obturator
Internus,
Gemellus
Superior,
Gemellus
Inferior,
Quadratus
Femoris
Gluteus
Medius
(posterior
fibers),
Gluteus
Minimus
(posterior
fibers),
Obturator
Externus,
Sartorius,
Biceps
Femoris
(long
head)
Kinetics
of
the
Hip
The
forces
going
through
the
hip
joint
vary
depending
on
the
activity.
In
bilateral
stance,
the
hips
are
in
an
extended
and
relatively
relaxed
position.
There
are
no
muscles
that
are
actively
working
to
keep
the
hips
extended.
This
is
due
to
the
fact
that
the
line
of
gravity
is
posterior
to
the
hip
joint,
thereby
putting
an
extension
moment
on
the
joint.
The
ligaments
located
anterior
to
the
joint
(iliofemoral,
ischiofemoral,
and
pubofemoral)
tighten
up
and
prevent
it
from
going
into
hyperextension.
In
reference
to
the
forces
at
the
hip,
there
is
an
equal
distribution
at
both
joints.
The
line
of
gravity
is
directed
downward
going
through
the
center
of
the
pelvis
(Figure
4).
Since
this
is
an
equal
distance
away
from
both
hip
joints,
the
moment
arms
are
identical,
thereby
distributing
equal
compression
forces
across
both
joints.
During
unilateral
stance,
the
forces
at
the
hip
joint
change.
As
one
leg
is
lifted
off
the
ground,
the
line
of
gravity
does
not
go
through
the
center
of
the
pelvis
anymore,
but
is
shifted
towards
the
stance
limb.
Because
of
this
shift,
the
pelvis
goes
into
an
adduction
moment
in
relation
to
the
stance
limb.
In
order
to
keep
the
pelvis
in
a
neutral
position,
the
hip
abductors
of
the
stance
limb
must
generate
enough
force
to
counterbalance
the
adduction
torque
moment.
This
puts
all
of
the
compression
force
on
the
joint,
which
amounts
to
approximately
3-­‐4
times
the
body
weight.
If
the
hip
abductors
are
incapable
of
producing
enough
force
to
counterbalance
the
adduction
moment
of
the
hip,
a
trendelenburg
gait
may
occur.
One
way
to
compensate
for
this
is
a
lateral
trunk
lean
towards
the
stance
limb.
The
moment
arm
of
the
abductors
remains
the
same,
but
the
moment
arm
of
the
line
of
gravity
is
decreased.
This
decreases
the
gravitational
pull
of
the
pelvis
into
an
adduction
moment,
thereby
decreasing
the
amount
of
counterforce
needed
from
the
hip
abductors.
Figure
4.
Weight
vector
through
the
pelvis

11. 11
The
biomechanics
of
the
hip
will
also
change
depending
on
the
amount
of
coxa
vara
or
coxa
valga
present.
In
a
normal
hip
joint,
the
angle
of
inclination
of
the
femoral
neck
is
approximately
125°.
With
coxa
vara,
the
angle
of
inclination
is
less
than
125°,
and
in
coxa
valga,
the
angle
is
greater
than
125°.
In
coxa
vara,
the
moment
arm
for
the
abductors
increases.
The
abductors
have
a
longer
lever
arm
to
work
with
and
can
create
more
torque.
However,
the
abductors
are
not
at
their
optimal
length
for
force
production
in
this
position,
and
there
is
increased
torque
on
the
femoral
neck.
This
can
result
in
a
fracture.
In
coxa
valga,
the
moment
arm
of
the
abductors
decreases,
which
allows
the
muscles
to
be
at
a
more
optimal
length
for
force
production.
This
also
decreases
the
torque
on
the
femoral
neck.
Since
the
moment
arm
is
decreased
in
this
position,
the
abductors
must
work
harder
to
produce
the
same
amount
of
force
needed
to
keep
the
pelvis
in
a
neutral
position
(Figure
5).
Muscular
Effects
on
Kinetics
Muscles
play
a
large
role
in
the
biomechanics
of
the
hip.
How
they
influence
the
hip
depends
on
where
they
are
located
in
relation
to
the
joint
and
their
line
of
pull.
For
this
reason,
a
muscle
may
be
an
internal
rotator
in
one
position
but
an
external
rotator
in
a
different
position.
Hip
Flexors
The
hip
flexors
are
located
anterior
to
the
joint.
Flexion
can
occur
in
a
pelvic-­‐on-­‐
femur
situation
or
a
femur-­‐on-­‐pelvic
situation.
The
movement
in
pelvis-­‐on-­‐femur
is
an
anterior
tilt.
A
force-­‐couple
relationship
between
the
back
extensors
and
the
hip
flexors
create
the
pelvic
tilt.
The
hip
flexors
rotate
around
the
medial/lateral
axis
of
the
hip
while
the
back
extensors
extend
resulting
in
lumbar
lordosis.
In
a
femur-­‐on-­‐pelvis
situation,
the
muscles
contract
and
the
femur
is
brought
up
towards
the
trunk
while
the
abdominal
muscles
contract
to
stabilize
the
pelvis
and
counter
the
anterior
tilt.
The
primary
and
secondary
movers
of
hip
flexion
can
be
found
in
Table
3.
Iliopsoas
is
the
major
hip
flexor
and
is
a
combination
of
two
muscles.
It’s
position
along
with
its
cross
sectional
area
makes
it
a
strong
hip
flexor.
Iliopsoas
is
located
to
have
optimal
pull
to
flex
the
hip
both
in
an
anatomical
start
position
as
well
as
when
the
hip
is
flexed
to
90°.
When
the
hip
is
flexed
at
90°
(as
in
a
sitting
position),
all
other
primary
hip
flexors
are
insufficient
to
flex
the
hip
further.
Because
iliopsoas
has
many
points
of
origin,
and
it
has
a
large
cross
sectional
area,
it
is
able
to
flex
the
hip
past
90°
from
a
sitting
position.
Hip
Extension
The
primary
hip
extensors
are
gluteus
maximus
and
the
hamstrings.
Gluteus
maximus
has
the
most
hip
extension
power,
due
to
its
large
cross
sectional
area,
along
with
its
large
moment
arm.
The
optimal
position
for
it
to
be
able
to
produce
the
most
extension
force
is
starting
in
the
neutral
position,
and
peaks
at
70°.
Although
it
is
a
strong
hip
extensor,
it
is
activate
predominately
when
it
is
up
against
resistance
that
is
greater
than
the
weight
of
the
limb.
Unlike
gluteus
maximus,
the
hamstrings
have
a
smaller
moment
arm,
and
a
cross
sectional
area
that
is
significantly
smaller.
It
is
a
two-­‐joint
muscle
that
consists
of
three
muscle
bellies.
The
hamstrings
group
differs
from
gluteus
maximus
in
that
Figure
5.
Decreased
moment
arm
due
to
coxa
valga

12. 12
its
moment
arm
for
extension
increases
with
hip
flexion
up
until
35°,
and
then
decreases
thereafter.
Once
the
hip
flexes
past
90°,
the
hamstrings
contribute
very
little
to
hip
extension.
Hip
Adductors
The
hip
adductors
function
in
three
different
planes,
but
they
do
not
adduct
within
all
planes.
As
mentioned
earlier,
the
muscle’s
line
of
pull
along
with
joint
position
will
determine
the
motion
at
the
joint.
The
hip
adductors
move
in
the
frontal
plane,
the
sagittal
plane,
and
the
transverse
plane.
In
the
frontal
plane,
the
adductors
adduct
the
femur.
In
the
sagittal
plane,
the
adductors
act
as
hip
flexors
and
extensors.
Which
movement
it
will
elicit
is
dependent
on
where
the
muscle’s
line
of
pull
is,
relative
to
the
joint
axis.
For
example,
when
the
hip
is
extended,
the
line
of
pull
falls
anterior
to
the
joint
axis,
which
gives
the
muscle
a
flexion
moment.
When
the
hip
is
flexed
to
approximately
100°,
the
line
of
pull
falls
posterior
to
the
joint
axis,
and
this
gives
the
muscle
an
extension
moment.
For
this
reason,
the
hip
adductors
are
considered
to
be
one
of
the
primary
and
secondary
movers
for
hip
flexion,
and
a
secondary
mover
for
hip
extension.
Hip
Abductors
Hip
abductors
are
very
important,
as
they
are
the
primary
muscles
that
produce
the
counterforce
necessary
to
keep
the
pelvis
in
a
neutral
position
during
single
limb
stance.
See
Table
3
for
a
list
of
primary
and
secondary
hip
abductors.
The
primary
hip
abductors
are
gluteus
medius
and
gluteus
minimis.
Along
with
abducting
the
femur,
they
work
to
stabilize
the
pelvis
a
mentioned
above
in
the
kinetics
section.
Hip
External
Rotators
The
primary
external
rotators
are
mostly
all
short
muscles
and
are
listed
in
the
table
above
in
Table
3.
These
muscles
are
predominately
used
in
a
closed-­‐chain
position
which
involves
cutting
and
pivoting.
Since
the
muscles
are
positioned
almost
perpendicular
to
the
shaft
of
the
femur,
their
optimal
position
to
perform
external
rotation
is
in
the
neutral
position.
When
the
hip
is
flexed,
obturator
internus
and
the
gluteus
muscles
external
moment
arm
decreases.
However,
due
to
the
origin
and
insertion
sites
of
piriformis,
hip
flexion
pass
90°
turns
piriformis
into
an
internal
rotator.
Hip
Internal
Rotators
The
hip
joint
does
not
have
any
primary
internal
rotators.
The
secondary
rotators
are
listed
in
Table
3,
which
is
mainly
comprised
of
the
adductors.
These
muscles
have
three
times
the
medial
rotation
torque
when
the
hip
is
flexed
compared
to
extended.
Joint
Configuration
of
the
Femoroacetabular
Joint
The
femoroacetabular
joint
is
synovial
ball
and
socket
joint
that
consists
of
the
union
of
the
head
of
the
femur
and
the
acetabulum.
Synovial
joints
have
specific
characteristics.
The
joint
usually
includes
a
surrounding
joint
capsule,
a
joint
cavity
with
synovial
fluid,
and
articular
cartilage
covering
the
bone.
The
femoroacetabular
joint
has
a
thick
joint
capsule
that
includes
the
merging
of
the
iliofemoral
ligament,
ischiofemoral
ligament,
and
the
pubofemoral
ligament.
The
joint
also
contains
synovial
membranes
that
secrete
synovial
fluid
into
the
joint
cavity
and
act
as
lubrication.
Finally,
both
the
acetabulum
and
the
head
of
the
femur
are
covered
with
articular
cartilage.

13. 13
The
lunate
surface
of
acetabulum
is
covered
in
hyaline
cartilage
that
creates
a
horseshoe
surface.
This
is
the
area
that
has
direct
contact
with
the
head
of
the
femur.
The
transverse
acetabular
ligament
attaches
to
both
ends
to
complete
the
circle.
Lastly,
in
order
to
deepen
the
acetabulum
and
to
create
more
surface
area,
the
acetabular
labrum
spans
the
entire
rim
of
the
socket.
It
also
helps
to
enhance
joint
stability
by
creating
a
sealing
effect,
maintaining
negative
intra-­‐capsular
pressure.
The
configuration
of
the
femur
also
impacts
the
joint
and
the
type
of
forces
that
act
upon
it.
The
angle
of
inclination
is
the
angle
between
the
head
of
the
femur
and
the
neck
of
the
femur
in
the
frontal
plane.
Normally,
this
angle
is
approximately
125°.
When
the
angle
is
smaller
than
125°,
this
is
known
as
coxa
vara
while
an
angle
larger
than
125°is
known
as
coxa
valga
(Figure
6).
This
angle
difference
changes
the
amount
of
force
as
well
as
where
the
force
acts
upon
the
hip
(see
biomechanics
section).
Another
angle
formed
by
the
head
and
neck
of
the
femur
is
the
angle
of
torsion.
The
normal
degree
for
an
adult
is
approximately
10°-­‐15°.
When
the
angle
is
smaller,
it
is
called
femoral
retroversion,
and
when
the
angle
is
larger
it
is
called
anteversion.
(Figure
7).
Changes
in
this
angle
also
have
implications
on
biomechanics.
For
example,
femoral
anteversion
may
have
a
negative
effect
on
hip
biomechanics
by
decreasing
the
joint
stability.
The
head
of
the
femur
is
more
exposed
anteriorly
and
this
puts
the
abductors
in
a
less
than
optimal
position
for
force
production.
As
mentioned
previously,
the
femoroacetabular
joint
is
known
for
its
ability
to
provide
stability
while
being
able
to
perform
a
wide
range
of
motions.
The
arthrokinematics
and
osteokinematics
of
the
hip
joint
allow
for
this
wide
variety
of
movement.
This
is
described
in
the
biomechanics
section.
Ligaments
of
the
Femoroacetabular
Joint
The
ligaments
of
the
hip
joint
are
the
strongest
in
the
body.
This
is
due
to
the
fact
that
the
hip
must
be
able
to
support
the
weight
of
the
body
and
not
dislocate.
One
of
the
strongest
ligaments
of
the
hip
is
the
iliofemoral
ligament,
also
known
as
the
Y
ligament.
The
Y
ligament,
along
with
the
other
ligaments,
spans
the
entire
joint.
The
thickest
areas
of
the
Y
ligament
are
located
anterior
to
the
hip
to
prevent
hyperextension
of
the
joint.
Figure
7.
Femoral
anteversion
and
retroversion
Figure
6.
Femoral
angle
of
inclination

14. 14
Table
4.
Ligaments
of
the
Femoroacetabular
Joint
Along
with
the
ligaments
of
the
hip
joint,
there
are
other
structures
that
constrain
the
joint.
The
acetabular
labrum
increases
the
surface
area
that
the
head
of
the
femur
has
direct
contact
with.
This
increase
in
surface
area
helps
decrease
a
possibility
of
dislocation.
The
joint
capsule
is
also
another
structure
that
constrains
the
joint
and
lies
under
the
ligaments.
The
three
main
ligaments
of
the
hip
joint
merge
together
to
help
contribute
to
the
joint
capsule.
The
joint
capsule
covers
the
head
and
neck
of
the
femur.
It
is
thickest
in
the
superior
anterior
portion
of
the
hip
and
thinnest
on
the
posterior
hip.
It
helps
constrain
the
joint
in
all
directions
but
is
most
effective
with
anterior
hip
dislocation.
Many
layers
of
large
muscles
also
surround
the
hip.
The
muscle
not
moves
the
hip
joint
but
serves
as
an
extra
barrier
to
contain
the
hip
within
the
joint.
The
most
muscle
bulk
around
the
hip
includes
the
gluteus
muscles
located
on
the
posterior
aspect
of
the
joint.
They
help
prevent
a
posterior
dislocation.
Common
Pathology
of
the
Femoroacetabular
Joint
Femoroacetabular
Impingement
(FAI)
Femoroacetabular
Impingement
is
a
problem
with
the
acetabulum
and
the
femoral
head
not
fitting
properly.
It
may
lead
to
reduced
range
of
motion
and
hip
and
groin
pain.
There
are
two
types
of
FAI:
Cam
impingement
and
Pincer
Impingement.
Cam
impingement
Ligament
Attachments
Function
Iliofemoral
Ligament
Anterior
inferior
iliac
spine
to
intertrochanteric
line
of
the
femur
Prevents
hyperextension
of
hip
Ischiofemoral
Ligament
ischium
posterior
to
the
acetabulum
to
greater
trochanter
&
iliofemoral
ligament
Helps
limit
extension
of
the
femur
Pubofemoral
Ligament
Iliopubic
eminence
and
superior
pubic
ramus
and
merges
in
with
the
joint
capsule/fibers
of
iliofemoral
ligament
Limits
extension
and
abduction
of
the
hip.
Primary
role
is
to
prevent
over
abduction
of
the
hip.
Ligamentum
Teres
Fovea
of
the
femoral
head
to
acetabular
notch
and
transverse
acetabular
ligament
When
hip
flexed
10º,
tightens
with
lateral
rotation.
Conduit
for
blood
supply
to
head
of
femur.
Transverse
ligament
Lateral
inferior
boundary
of
the
acetabular
labrum
to
medial
inferior
boundary
of
the
acetabular
labrum
Completes
acetabular
labrum
rim
and
prevents
inferior
displacement
of
the
head
of
the
femur

15. 15
involves
the
abnormal
shape
of
the
femoral
head,
sometimes
called
a
“pistol-­‐grip”
deformity.
The
cause
is
unknown,
although
some
propose
that
it
has
to
do
with
a
recalcification
of
the
proximal
femoral
epiphysis.
Others
suggest
that
it
is
from
abnormal
stresses
on
the
femur.
This
extra
protuberance
on
the
head
of
the
femur
does
not
allow
for
good
clearance
of
the
acetabulum
when
flexion
or
abduction
occurs
at
the
joint.
If
this
is
repeated
over
long
periods
of
time,
wearing
of
the
articular
cartilage
and
labrum
may
occur.
Labral
tears
and
injury
usually
accompany
FAI
for
this
reason.
The
labrum
is
innervated,
so
as
a
result,
the
person
may
experience
pain
in
the
hip
and
groin
area.
Pincer
impingement
occurs
when
the
acetabulum
is
too
large
for
the
femoral
head.
This
can
be
due
to
having
a
deeper
acetabular
fossa,
or
the
acetabulum
being
in
a
retroverted
position.
When
the
hip
is
flexed
or
abducted,
the
femoral
head
may
compress
surrounding
soft
tissue
or
the
superior
labrum,
causing
pain
in
the
hip
and
groin
area.
If
the
impingement
persists
for
longer
periods
of
time,
the
labrum
may
undergo
ossification
making
the
overhang
worse.
Osteoarthritis
(OA)
Osteoarthritis
is
the
most
common
condition
of
the
hip.
It
occurs
when
the
articular
surfaces
of
the
joint
are
worn
down
and
there
is
a
rubbing
of
bone
on
bone
during
movements.
There
are
many
ways
OA
can
develop.
A
history
of
labral
tears
or
CAM
impingement
will
increase
the
likelihood
of
developing
OA.
Jaypee
mentions
that
two
predictive
factors
of
developing
OA
include
having
previous
musculoskeletal
injuries
and
a
work
history
that
is
physically
demanding
such
as
manual
labor.
It
is
also
mentioned
that
the
two
factors
related
to
idiopathic
hip
OA
is
aging
and
weight
gain.
OA
is
a
degeneration
of
the
cartilage
within
the
joint
and
it
is
commonly
thought
that
repetitive
weight
bearing
may
contribute
to
its
progression.
Jaypee
mentions
that
it
is
not
the
repetitive
weight
bearing
but
rather
the
lack
of
joint
forces
on
the
joint
that
may
play
a
role
in
developing
OA.
This
is
due
to
the
fact
that
compression
on
the
articular
cartilage
actually
nourishes
the
joint.
Symptoms
of
hip
OA
include
hip
stiffness,
anterior
groin
pain,
and
decreased
range
of
motion
in
extension
and
internal
rotation.
Fractures
of
the
Pelvis
Hip
fractures
in
older
adults
are
very
common
and
occur
at
a
rate
of
98/100,000
people
a
year.
Older
adults
are
at
a
higher
risk
for
fractures
due
to
their
increase
in
fall
risk.
Hip
fractures
can
occur
for
a
variety
of
reasons.
As
mentioned
earlier
in
the
biomechanics
section,
the
hip
takes
on
a
compression
force
of
2-­‐3
times
the
body
weight
when
standing
on
one
limb,
which
occurs
during
walking.
The
femur
must
be
healthy
enough
to
withstad
the
force
on
the
neck
of
the
femur.
Unfortunately,
as
a
person
ages,
there
is
a
decrease
in
trabecular
density
as
well
as
cortical
bone
mass.
This
may
result
in
a
proximal
fracture
to
the
femur.
Also,
due
to
the
decreased
integrity
of
the
bone,
a
fall
could
easily
cause
a
fracture.
Another
factor
that
may
cause
a
fracture
is
loss
of
arterial
supply
to
the
head
of
the
femur
(avascular
necrosis).
The
head
of
the
femur
is
mainly
supplied
by
the
medial
circumflex
artery.
If
there
is
any
trauma
to
the
area
that
disrupts
the
blood
supply,
bone
death
may
occur
making
it
more
susceptible
to
injury.

16. 16
The
Pubic
Symphysis
Joint
The
pubic
symphysis
(Figure
8)
is
located
in
the
anterior
midline
of
the
pelvis
and
consists
of
the
medial
articulating
surfaces
of
the
right
and
left
pubic
bones
united
by
a
fibrocartilaginous
interpubic
disc.
In
addition
to
the
sacroiliac
joint,
the
pubic
symphysis
serves
as
an
articulation
site
of
the
right
and
left
innominates.
The
pubic
symphysis
is
sometimes
referred
to
as
the
symphysis
pubis.
This
joint
is
relatively
immobile
and
is
classified
as
a
secondary
cartilaginous
joint.
The
pubic
symphysis
functions
to
resist
tension,
shearing,
and
compression
of
the
pelvis
during
weight
bearing
activities,
such
as
walking
and
during
childbirth
in
women.
Research
regarding
the
precise
innervation
of
the
pubic
symphysis
is
lacking.
However,
in
a
systematic
review,
Becker
et
al
(2010)
found
the
innervation
described
as
coming
from
the
pudendal
and
genitofemoral
nerves,
and
branches
of
the
iliohypograstric,
ilioinguinal
nerves.
Becker
also
found
the
joint
to
be
supplied
by
the
pubic
branch
of
the
obturator
artery
and
branches
of
the
inferior
epigastric
artery
and
external
pudendal
artery.
As
most
fibrocartilaginous
tissues
depend
on
diffusion
of
nutrients
from
adjacent
blood
vessels
(Neumann
2010),
the
center
of
the
fibrocartilaginous
disc
will
rely
on
diffusion
from
the
obturator,
inferior
epigastric,
or
external
pudendal
arteries.
Tissue
Layers
from
Superficial
to
Deep
• Integumentary
o Epidermis
o Dermis
• Subcutaneous
o Fascia
o Adipose
• Muscles
o Rectus
Abdominis
o External
Oblique
o Internal
Oblique
o Transversus
Abdominis
o Adductor
longus
o Adductor
Magnus
o Adductor
Brevis
• Neurovascular
o Nervous
Tissue
! Iliohypogastric
nerve
! Ilioinguinal
nerve
! Pudendal
nerve
! Genitofemoral
nerve
Figure
8.
The
Pubic
Symphysis

17. 17
o Vascular
Tissue
! Pubic
branches
of
obturator
artery
! Inferior
epigastric
artery
! External
pudendal
artery
• Ligaments
o Superior
Pubic
Ligament
o Arcuate
Pubic
Ligament
o Anterior
Pubic
Ligament
o Posterior
Pubic
Ligament
• Joint
Capsule/Tissue
o Hyaline
articular
cartilage
o Fibrocartilaginous
disc
• Bone
o Pubis
bones
of
the
Innominates
Table
5.
Joint
Motions
at
the
Pubic
Symphysis
Joint
Motion
Primary
Movers
Secondary
Movers
Superior/Inferior
Translation
Rectus
abdominis,
internal
oblique,
external
oblique,
transversus
abdominis,
adductor
longus
N/A
Rotation
Rectus
abdominis,
internal
oblique,
external
oblique,
transversus
abdominis,
adductor
longus
N/A
Compression/Traction
Rectus
abdominis,
internal
oblique,
external
oblique,
transversus
abdominis,
adductor
longus
N/A
****The
muscles
listed
act
indirectly
on
the
relatively
rigid
pubic
symphysis.
However,
the
muscles
included
in
the
table
reinforce
the
joint
via
attachment
of
the
aponeuroses
from
muscles
of
the
anterior
abdominal
wall
and
muscles
of
the
lower
extremities
to
the
pubic
bones.
Biomechanics
of
the
Pubic
Symphysis
The
pubic
symphysis
is
a
relatively
immobile
cartilaginous
joint
that
is
subjected
to
a
variety
of
forces.
For
example,
during
standing
activities,
the
inferior
portion
of
the
symphysis
is
subjected
to
traction
forces
while
the
superior
region
is
subjected
to
compression
forces.
The
pubic
symphysis
withstands
compression
forces
with
sitting
and
simultaneous
compression
and
shearing
forces
during
single-­‐leg
stance
(Becker,
2010).
The
pubic
symphysis
can
experience
translation
in
the
sagittal
and
transverse
plane.
However,
Neumann
describes
the
joint
as
only
having
up
to
2
mm
of
translation.
Becker
et
al
describe
rotation
of
up
to
3°
at
the
pubic
symphysis
in
the
frontal
and
sagittal
planes.
The
pubic
symphysis
primary
function
is
stabilization
and
functions
to
transfer
forces
from
the
trunk
to
the
lower
extremities.
There
are
no
muscles
that
act
as
primary
movers
for
the

18. 18
stable
pubic
symphysis.
The
anterior
surface
of
the
adjacent
pubic
bones
serve
as
an
attachment
site
for
the
rectus
abdominus,
internal
abdominal
oblique,
transversus
abdominus,
and
the
adductor
longus,
but
these
muscles
do
not
directly
initiate
movement
at
the
pubic
symphysis
joint.
Accessory
motions
and
open/closed
pack
positions
are
not
experienced
at
this
joint
due
to
the
high
degree
of
stability
offered
by
the
pubic
ligaments.
Joint
Configuration
of
the
Pubic
Symphysis
The
articular
surfaces
of
the
right
and
left
pubic
bones
are
lined
with
hyaline
cartilage
and
are
joined
by
the
fibrocartilaginous
interpubic
disc.
The
surfaces
are
slight
convex
in
shape,
likely
designed
to
resist
shearing
forces.
Due
to
the
relative
immobility
of
the
joint,
the
motion
that
occurs
pubic
symphysis
is
not
dependent
on
the
convexity
of
the
articulating
surfaces
but
on
the
tensile,
shear
and
compressive
forces
experienced
at
the
joint.
Arthokinematic
movements
of
superior
or
inferior
glide
of
the
pubis
bones
up
to
2
mm
occur
in
relation
to
the
forces
experienced
at
the
joint.
Table
6.
Ligaments
of
the
Pubic
Symphysis
(Figures
9
&
10)
Ligament
Attachments
Function
Associated
Constraints
Superior
pubic
ligament
Lateral
pubic
crest
and
pubic
tubercle
to
contralateral
lateral
pubic
crest
and
tubercle,
bridging
superior
margin
of
symphysis
Reinforce
superior
aspect
of
joint
N/A
Arcuate
(inferior)
pubic
ligament
Inferior
rami
of
pubis
to
contralateral
inferior
rami
of
pubis
Reinforce
inferior
aspect
of
joint
N/A
Anterior
pubic
ligament
Joins
with
interpubic
disc
and
aponeurotic
expansions
of
rectus
abdominus,
transversus
abdominus,
internal
abdominal
oblique,
and
adductor
longus
Reinforce
anterior
aspect
of
joint
Adductor
longs,
rectus
abdominis
aponeurosis,
internal
oblique
aponeurosis,
and
transversus
abdominis
aponeurosis
Posterior
pubic
ligament
Continuous
with
periosteum
of
posterior
aspect
of
pubic
bones
Reinforce
posterior
aspect
of
joint
N/A

19. 19
Common
Pathology
of
the
Pubic
Symphysis
Osteitis
Pubis
Osteitis
pubis
is
a
common
pathology
of
the
pubic
symphysis
that
results
from
overuse
or
shear
injuries
and
subsequent
inflammation
around
the
joint.
This
injury
is
common
among
the
athlete
population.
Osteitis
pubis
often
needs
to
be
distinguished
between
an
inguinal
hernia
and
an
adductor
strain
as
these
injuries
present
similarly
and
tend
to
occur
in
similar
populations.
For
differential
diagnosis
purposes,
tenderness
directly
over
the
pubic
symphysis
may
be
the
best
indicator
of
osteitis
pubis.
Symphysis
Pubis
Dysfunction
Symphysis
pubis
dysfunction
occurs
in
women
during
pregnancy.
Becker
describes
how
the
hormones
associated
with
pregnancy
can
increase
the
laxity
at
the
pubic
symphysis.
Resulting
pubic
instability
can
cause
pain
and
difficulty
with
weight-­‐bearing
activities
and
bed
mobility
for
pregnant
women.
The
joint
may
also
be
disrupted
and
widened
during
childbirth
leading
to
impaired
pelvic
stability
in
the
postpartum
period.
Figure
10:
Superior
view
pubic
ligaments
Figure
9:
Anterior
view
of
pubic
symphysis
ligaments

20. 20
The
Sacroiliac
Joint
The
sacroiliac
(SI)
joints
(Figure
11)
mark
the
transition
from
the
caudal
axial
skeleton
to
the
lower
appendicular
skeleton.
The
SI
joint
is
located
anterior
to
the
posterior
superior
iliac
spine
of
the
ilium.
The
relatively
rigid
joint
is
formed
by
the
articulation
between
the
auricular
(ear-­‐shaped)
surface
on
the
lateral
aspect
of
the
sacrum
that
corresponds
with
sacral
levels
S1,
S2,
S3
(Vleeming
2012)
and
the
auricular
surface
of
the
medial
aspect
of
the
ilium.
Both
articulating
surfaces
are
covered
with
hyaline
cartilage.
The
articular
surface
of
the
SI
joint
has
been
described
as
having
a
boomerang
shape
with
the
open
angle
facing
posteriorly
(Figure
12).
During
early
childhood,
the
SI
demonstrates
the
classical
characteristics
of
a
diarthrodial
synovial
joint
with
smooth
surfaces
and
considerable
mobility.
However,
over
time,
between
puberty
and
adulthood
the
joint
transforms
from
a
diarthrodial
joint
to
a
modified
synarthrodial
joint,
as
explained
by
Neumann.
The
articular
surfaces
become
rough
and
irregular,
embedding
the
subchondral
bone
within
the
articular
cartilage
of
the
joint
order
to
resist
excessive
movements
between
the
sacrum
and
ilium.
Several
ligaments,
some
of
which
are
the
strongest
in
the
body,
reinforce
the
rigidity
of
the
joint.
The
SI
joint
is
primarily
designed
for
stability.
The
joints
transfer
loads
between
the
vertebral
column
and
the
lower
extremities.
The
SI
joints
relieve
the
stress
experienced
by
the
pelvic
ring
secondary
to
trunk
and
lower
extremity
movement
and
ground
reaction
forces.
Specific
innervation
of
the
sacroiliac
joint
has
not
been
verified
in
the
literature.
However,
Vleeming
(2012)
reports
dorsal
rami
L5-­‐S3
to
be
consistently
included
in
various
studies
of
SI
joint
innervation.
Nociceptive
axons
(C-­‐fibers
and
A-­‐delta
fibers)
have
been
found
in
the
joint,
responsible
for
pain
perception
from
the
SI
joint
(Vleeming
2012).
The
posterior
division
of
the
internal
iliac
artery,
namely
iliolumbar,
lateral
sacral,
and
superior
gluteal
arteries,
provide
blood
supply
to
the
sacroiliac
joint.
Tissue
Layers
from
Superficial
to
Deep
• Integumentary
o Epidermis
o Dermis
Figure
11.
Anterior
view
of
SI
joint
Figure
12.
Boomerang
shape
of
auricular
surfaces
of
ilium
and
sacrum

21. 21
• Subcutaneous
o Adipose
o Thoracolumbar
fascia
! Anterior
layer
! Middle
layer
! Posterior
layer
• Muscles
o Latissimus
Dorsi
o Gluteus
Maximus
o External
Oblique
o Internal
Oblique
o Erector
Spinae
muscles
o Transversus
Abdominis
o Lumbar
Multifidus
o Quadratus
lumborum
o Gluteus
Medius
o Piriformis
o Iliacus
(covering
anterior
SI
joint)
• Ligaments
o Anterior/Ventral
sacroiliac
ligament
o Posterior
Sacroiliac
ligament
o Interspinous
ligament
o Sacrotuberous
ligament
o Sacrospinous
ligament
o Iliolumbar
ligament
• Joint
Capsule
o Fibrous
capsule
o Synovial
membrane
o Synovial
fluid
o Hyaline
cartilage
• Bone
o Tuberosity
and
auricular
surface
of
ilium
o Tuberosity
and
auricular
surface
of
the
sacrum
Table
7.
Joint
Motions
at
the
Sacroiliac
Joint
Joint
Motion
Primary
Movers
Secondary
Movers
Nutation
(Gravity
creates
nutation
torque),
Latissimus
dorsi,
biceps
femoris,
rectus
abdominus,
internal
and
external
oblique,
transversus
abdominus
N/A
Counternutation
Iliopsoas,
rectus
femoris,
erector
spinae
N/A
Stability
Erector
spinae,
quadratus
lumborum,
lumbar
multifidus,
rectus
Muscle
activation
causes
tension
in
ligaments,

22. 22
abdominus,
internal
oblique,
external
oblique,
transversus
abdominus,
biceps
femoris,
gluteus
maximus,
latissimus
dorsi,
iliacus,
piriformis
compressing
surfaces
of
SI
joint
**The
muscles
listed
act
indirectly
on
the
relatively
rigid
SI
joint.
However,
the
muscles
included
in
the
table
reinforce
and
stabilize
the
SI
joint
during
dynamic
activities
such
as
lifting,
running,
and
carrying
via
attachments
to
the
thoracolumbar
fascia
and
sacrospinous
and
sacrotuberous
ligaments.
Biomechanics
of
the
Sacroiliac
Joint
The
sacroiliac
joint
has
relatively
limited
mobility,
and
unlike
most
joints
in
the
body,
there
are
no
muscles
acting
directly
across
the
SI
joint.
The
rotational
and
translational
movements
that
occur
at
the
SI
joint
are
complex.
The
motions
do
not
occur
about
a
fixed
axis,
but
rather
include
a
combination
of
parallel
and
angular
movements
(Gordon
1991).
The
motion
at
the
SI
joint
has
best
been
described
as
nutation
and
counternutation,
which
occur
in
a
near-­‐sagittal
plane
about
a
near
medial-­‐lateral
axis
of
rotation
that
traverses
the
interosseous
ligament.
Nutation
(sometimes
called
sacral
flexion)
refers
to
an
anterior,
inferior
motion
of
the
sacral
promontory
and
a
posterior,
superior
movement
of
the
sacral
apex.
Counternutation
(sacral
extension)
is
defined
as
a
posterior,
superior
movement
of
the
sacral
promontory
and
anterior,
superior
move
of
the
sacral
apex.
Nutation
and
counternutation
can
be
described
as
either
sacral-­‐on-­‐iliac
rotation,
by
iliac-­‐on-­‐sacral
rotation,
or
by
both
motions
simultaneously
(Figure
13).
For
example,
nutation
can
be
described
as
anterior
sacral-­‐on-­‐iliac
rotation
or
posterior
iliac-­‐on-­‐
sacral
rotation
or
anterior
sacral
rotation
with
posterior
iliac
rotation.
Gordon
and
Alderink
describe
the
role
of
SI
joint
motion
in
lumbopelvic
rhythm
during
functional
activities.
During
trunk
flexion,
the
lumbar
spine
moves
into
flexion,
the
pelvis
anteriorly
rotates,
and
the
sacrum
follows
with
nutation
or
sacral
flexion.
Upon
returning
to
stand,
the
sacrum
counternutates
(extends)
as
it
follows
the
lumbar
spine
and
pelvis.
The
magnitude
movement
at
the
SI
joint
is
significantly
limited.
Translation
at
the
SI
joint
is
limited
to
1-­‐4
mm
and
Foley
(2006)
found
the
joint
motion
in
the
transverse
or
longitudinal
planes
does
not
exceed
2-­‐3
degrees.
Strong
ligaments
surround
the
joint
to
limit
excessive
motion
and
reinforce
the
joint’s
stability.
Slight
motion
with
reinforced
stability
at
the
SI
joints
is
vital
for
attenuating
forces
between
the
axial
skeleton
and
the
lower
extremities.
Figure
13.
Nutation
and
Counternutation
of
the
SI
joint

23. 23
Joint
Configuration
of
the
Sacroiliac
Joint
The
articulation
between
the
sacrum
and
the
ilium
contains
elevations
and
depressions
of
the
articulating
surfaces,
creating
an
interlocking
mechanism
between
the
two
bones.
Foley
(2006)
describes
the
ilium
to
have
a
relative
convex
surface
and
the
sacrum
to
have
a
more
concave
shape
at
the
SI
articulation
site.
Because
the
plane
of
articular
surfaces
is
mostly
vertical
in
orientation,
nutation
at
the
SI
joint
increases
compression
and
consequential
stability
between
the
joint
surfaces.
Therefore,
full
nutation
is
considered
to
be
the
close-­‐packed
position
of
the
SI
joint.
Gravity,
ligaments,
and
activation
of
surrounding
muscles
create
nutation
torque.
Load
transfer
through
the
pelvic
girdle
is
more
effective
when
the
sacrum
is
in
a
nutated
position.
Table
8.
Ligaments
of
the
Sacroiliac
Joint
(Figure
14)
Ligament
Attachments
Function
Anterior/Ventral
Sacroiliac
Ligament
Anterior
and
inferior
borders
of
the
iliac
auricular
surface
to
anterolateral
sacrum
Resists
anterior
movement
and
nutation
of
the
sacral
promontory
Posterior/Dorsal
Sacroiliac
Ligament
Posterolateral
border
of
3rd
and
4th
segment
of
sacrum
to
lateral
ilium
near
iliac
tuberosity
and
posterior-­‐superior
iliac
spine;
thoracolumbar
fascia,
erector
spinae
aponeurosis,
blends
with
sacrotuberous
ligament
to
attach
to
ischial
tuberosity
Resists
counter-­‐nutation
of
sacrum
Interosseous
Ligaments
Fills
space
that
is
posterior
and
superior
to
joint
between
lateral
sacral
crest
and
iliac
tuberosity
Considered
most
important
ligaments
directly
associated
with
SI
joint;
Resists
excessive
movement
Iliolumbar
Ligament
Transverse
process
of
L5
to
medial
iliac
crest
Restricts
sagittal
plane
movement
Sacrotuberous
Ligament
Posterior-­‐superior
iliac
spine,
lateral
sacrum
and
coccyx,
blends
with
posterior
sacroiliac
ligament
to
attach
to
ischial
tuberosity
Secondary
source
of
stability;
restricts
nutation
Sacrospinous
Ligament
Inferior
lateral
border
of
sacrum
and
coccyx
to
ischial
spine
Secondary
source
of
stability;
restricts
nutation
An
associated
constraint
to
the
SI
joint
is
the
thoracolumbar
fascia,
which
restricts
excessive
movement
in
all
directions
of
motion.

24. 24
Common
Pathology
of
the
Sacroiliac
Joint
Low
Back
Pain
The
sacroiliac
joints
have
been
found
to
the
source
of
pain
in
15%-­‐30%
of
the
population
of
people
who
experience
chronic
low
back
pain.
Pain
originating
from
the
SI
joint
can
refer
to
multiple
areas
of
the
body
(Figure
15)
including
the
low
back
and
gluteal
region,
making
SI
joint
dysfunction
difficult
to
identify
and
to
treat.
SI
Dysfunction
SI
dysfunction
and
subsequent
pain
is
the
result
of
impaired
load
transfer
through
the
SI
joints.
Dysfunction
of
the
joint
can
be
secondary
to
trauma,
leg
length
discrepancies,
excessive
lumbar
lordosis,
joint
degeneration,
joint
stiffness,
or
displacement
such
as
an
upslip
or
downslip
of
the
joint.
The
SI
dysfunction
is
also
common
in
women
who
are
pregnant.
The
hormone
relaxin
is
released
in
pregnancy,
which
increases
laxity
of
the
ligaments
that
support
and
reinforce
joint.
A
widening
effect
at
the
SI
joint
occurs
in
preparation
for
childbirth.
However,
the
excessive
motion
available
at
the
joint
is
often
a
source
of
pain
and
aberrant
movement
patterns
for
the
mother.
Also,
athletes
involved
in
sports
that
require
frequent
unilateral
loading
of
the
lower
extremities
(such
as
in
kicking)
are
at
increased
risk
for
SI
dysfunction
(Foley).
Physical
therapists
can
test
for
SI
dysfunction
using
a
battery
of
motion
palpation
tests
such
as
the
sacral
thrust
and
Gillet
test.
Strengthening
of
surrounding
muscles
(especially
muscles
attaching
to
the
thoracolumbar
fascia)
can
help
improve
the
stability
of
the
SI
joint
and
reduce
pain
related
to
SI
dysfunction.
Figure
14.
Posterior
ligaments
of
the
SI
joint
(note:
interosseous
ligaments
are
deep
to
pictured
posterior
sacroiliac
ligament)
Figure
15.
SI
joint
referred
pain
patterns

25. 25
Introduction
to
the
Knee
Joint
Complex
The
knee
joint
is
the
largest
joint
in
the
body.
It
is
subject
to
compression
and
torque
during
activities
such
as
walking,
running,
jumping,
bending
and
squatting.
Bony
articulation
at
the
knee
joint
complex
is
relatively
unstable
and
must
rely
on
several
muscles
and
ligaments
for
structural
support
(Figure
1).
Located
in
the
middle
of
the
chain,
the
knee
is
highly
impacted
by
the
motions
occurring
at
the
hip
and
ankle
joints.
Due
to
it’s
location
in
the
chain,
and
its
unstable
boney
articulation,
the
knee
joint
complex
is
the
most
frequently
injured
joint
in
the
body.
The
knee
joint
complex
is
comprised
of
two
different
articulations,
the
tibiofemoral
joint
and
the
patellofemoral
joint.
These
two
joints
are
held
within
the
joint
capsule,
forming
a
synovial
hinge
joint.
Although
the
proximal
aspect
of
the
fibula
articulates
with
the
tibia
just
lateral
the
knee
joint,
it
is
not
involved
in
movement
at
the
knee.
The
tibiofemoral
and
patellofemoral
joints
work
together
to
allow
movement
in
two
planes
of
motion:
flexion
and
extension
in
the
sagittal
plane,
and
internal
and
external
rotation
in
the
transverse
plane.
Superior
and
inferior
gliding
at
the
patellofemoral
joint
are
necessary
to
allow
flexion
and
extension
at
the
tibiofemoral
joint.
During
extension,
the
patella
functions
to
increase
force
produced
by
the
quadriceps
femoris.
Various
pathologies
or
lack
of
proper
functioning
of
the
joints
and
associated
structures
can
lead
to
impairments
and
decreased
participation.
Neurovascular
Supply
Much
of
the
knee
joint
is
highly
vascularized
with
the
exception
of
a
portion
of
the
meniscus.
The
main
blood
supply
comes
from
branches
of
the
femoral
artery
which
then
becomes
the
popliteal
artery.
A
large
genicular
anastomosis
is
responsible
to
supply
blood
to
majority
of
the
knee
structures
and
surrounding
muscles.
However,
the
exception
is
the
inner
portion
of
the
menisci.
These
avascular
sections
then
have
inhibited
tissue
healing
after
an
injury
to
the
inner
portion
of
the
lateral
or
medial
meniscus.
The
femoral
artery
passes
down
the
posterior
aspect
of
the
thigh
and
transitions
into
the
popliteal
artery
to
supply
the
hamstring,
gastrocnemius,
soleus,
and
plantaris
musculature.
This
artery
runs
most
anterior
in
the
joint
before
splitting
into
Figure
1.
The
knee
Figure
2.
Anastomosis
around
the
knee

26. 26
the
anterior
and
posterior
tibial
arteries
at
the
distal
aspect
of
the
joint
capsule.
The
capsule
and
ligaments
of
the
knee
joint
are
supplied
by
five
collateral
branches
originating
from
the
popliteal
artery.
These
branches
form
the
genicular
anastomosis
(Figure
2)
which
surrounds
the
knee
joint
and
provides
adequate
blood
supply.
The
branches
include
the
superior
medial
and
lateral
geniculars,
the
inferior
medial
and
lateral
geniculars,
and
the
middle
genicular
artery.
In
the
case
that
the
popliteal
artery
is
obstructed,
such
as
in
a
long
duration
of
knee
extension,
the
anastomotic
branches
will
continue
to
provide
sufficient
blood
supply
to
the
knee.
Venous
return
is
transported
by
the
posterior
tibial
vein,
which
transitions
into
the
popliteal
vein
in
the
popliteal
fossa.
The
popliteal
vein
traverses
the
knee
joint
alongside
the
popliteal
artery
before
becoming
the
femoral
vein.
The
small
saphenous
vein
is
also
a
tributary
into
the
popliteal
vein
and
transports
blood
from
the
posterior
aspect
of
the
malleolus
superiorly
into
the
popliteal
fossa.
The
knee
and
surrounding
muscle
innervations
can
be
broken
up
into
four
different
compartments
supplied
by
separate
nerves:
anterior,
posterior,
medial
and
lateral
(Figure
3).
The
anterior
aspect
of
the
knee
and
thigh
muscles
are
innervated
through
the
femoral
nerve
while
muscles
of
the
posterior
and
lateral
aspects
receive
innervation
from
branches
of
the
sciatic
nerve
known
as
the
common
fibular
branch
and
the
tibial
branch
respectively.
The
medial
aspect
is
innervated
via
the
obturator
nerve
with
cutaneous
innervation
from
the
saphenous
cutaneous
nerve.
The
posterior
aspect
of
the
knee,
the
popliteal
fossa,
is
the
point
where
the
sciatic
nerve
splits
into
the
tibial
division
and
the
common
fibular
division
(Figure
4).
The
tibial
nerve
supplies
muscles
found
posterior
to
the
knee
joint
such
as
the
soleus,
gastrocnemius,
plantaris,
and
popliteus.
The
common
fibular
nerve
runs
on
the
lateral
aspect
of
the
joint,
following
the
medial
aspect
of
the
biceps
femoris,
and
wraps
closely
around
the
neck
of
the
fibular
where
it
is
subject
to
injury.
The
common
fibular
nerve
supplies
the
short
head
of
the
biceps
femoris.
The
posterior
cutaneous
nerve
of
the
thigh
provides
innervation
to
the
skin
posterior
to
the
knee
joint.
Figure
3.
Nerve
supply
Figure
4.
Popliteal
fossa
structures

27. 27
Table
1.
Muscles
Acting
on
the
Tibiofemoral
and
Patellofemoral
Joints
(Figure
5
&
6)
Muscle
Proximal
Attachment
Distal
Attachment
Segmental
Innervation
Peripheral
Innervation
Anterior
Region
Rectus
femoris
Anterior
inferior
iliac
spine
and
ilium
superior
to
acetabulum
Vastus
lateralis
Greater
trochanter
and
lateral
lip
of
linea
aspera
of
femur
Vastus
medialis
Intertrochanteric
line
and
medial
lip
of
linea
aspera
of
femur
Vastus
intermedius
Anterior
and
lateral
surfaces
of
shaft
of
femur
Quadriceps
tendon
and
attachments
to
base
of
patella
forming
patellar
ligament
to
tibial
tuberosity;
medial
and
lateral
vasti
also
attach
tibia
and
patella
via
patellar
retinacula
L2,
L3,
L4
Femoral
nerve
Articularis
Genu
Distal
anterior
shaft
of
femur
Proximal
portion
of
synovial
membrane
of
the
knee
L2,
L3,
L4
Femoral
nerve
Medial
Region
Sartorius
Anterior
superior
iliac
spine
and
superior
part
of
notch
inferior
to
it
Superior
portion
of
medial
surface
of
tibia
L2,
L3
Femoral
nerve
Gracilis
Body
and
inferior
ramus
of
pubis
Superior
portion
of
medial
surface
of
tibia
L2,
L3
Obturator
nerve
Lateral
Region
Tensor
fascia
latae
Anterior
superior
iliac
spine
and
external
lip
of
iliac
crest
Iliotibial
tract
L4,
L5,
S1
Superior
gluteal
nerve
Posterior
region
Semitendinosus
Medial
surface
of
superior
part
of
tibia
Semimembrano
-­‐sus
Ischial
tuberosity
Posterior
part
of
medial
condyle
of
tibia
L5,
S1,
S2
Tibial
division
of
sciatic
nerve
Biceps
femoris:
Long
head
Short
head
Long
head:
Ischial
tuberosity
Short
head:
linea
aspera
and
lateral
supracondylar
line
of
femur
Lateral
side
of
head
of
fibula
L5,
S1,
S2
Long
head:
Tibial
division
of
sciatic
nerve
Short
head:
Common
fibular
division
of
sciatic
nerve

28. 28
Tissue
Layers
from
Superficial
to
Deep
(Figure
7)
• Skin
o Epidermis
o Dermis
• Adipose
• Fascia
o Fascia
Latae
! Iliotibial
tract
! Intermuscular
septa
o Patellar
retinaculum,
medial
and
lateral
• Muscles
and
tendons
o Anteriorly
! Quadriceps
tendon
! Patellar
tendon
! Articularis
Genu
o Medially
! Semitendinosus
! Semimembranosus
! Sartorius
! Gracilis
o Posteriorly
! Gastrocnemius
! Plantaris
! Popliteus
o Laterally
! Biceps
femoris
• Bursa
o Anteriorly
! Suprapatellar
! Prepatellar
! Infrapatellar
o Medially
! Anserine
! Semimembranosus
o Laterally
! Subtendinosus
of
biceps
femoris
! Bursa
deep
to
Iliotibial
tract
• Neurovasculature
Gastrocnemius
Lateral
head:
lateral
aspect
of
lateral
condyle
of
femur
Medial
head:
popliteal
surface
of
femur
superior
to
medial
condyle
Posterior
surface
of
calcaneus
via
Achilles
tendon
Plantaris
Inferior
end
of
lateral
supracondylar
line
of
femur,
oblique
popliteal
ligament
Posterior
surface
of
calcaneus
via
Achilles
tendon
S1,
S2
Tibial
Nerve
Figure
7.
Sagittal
cut
of
the
knee

29. 29
o Common
fibular
nerve
o Tibial
nerve
o Sural
nerve
o Popliteal
artery
! Superior
medial
genicular
artery
! Superior
lateral
genicular
artery
! Middle
genicular
artery
! Inferior
medial
genicular
artery
! Inferior
lateral
genicular
artery
• Extracapsular
ligaments
o Anterolateral
ligament
o Lateral
collateral
ligament
o Medial
collateral
ligament
• Joint
Capsule
• Intracapsular
ligaments
o Posterior
cruciate
ligament
o Anterior
cruciate
ligament
• Menisci:
medial
and
lateral
• Articular
cartilage
of
femur
• Articular
cartilage
of
tibia
• Bones
o Patella
o Tibia
o Femur

30. 30
The
Tibiofemoral
Joint
The
tibiofemoral
joint
is
the
largest
of
the
knee
joint
complex
and
produces
most
of
the
movement
at
the
knee.
This
joint
undergoes
a
great
deal
of
impact
during
daily
activities.
Function
at
the
tibiofemoral
joint
is
vital
for
shock
absorption
in
closed-­‐
chain
activities
such
as
walking,
running,
squatting,
and
jumping.
The
tibiofemoral
joint
and
its
associated
structures
are
surrounded
by
a
thin
layer
of
fibrous
connective
tissue
called
the
joint
capsule.
This
capsule
is
lined
with
an
extensive,
thick
synovial
membrane
and
synovial
fluid,
giving
the
joint
its
classification
as
the
largest
synovial
joint
in
the
body.
The
synovial
fluid
allows
for
very
low
friction
within
this
mobile
joint.
Deep
to
the
joint
capsule
are
as
many
as
14
bursae
(Figure
8).
These
are
found
at
areas
producing
high
friction
with
movement
where
tissues
articulate.
The
tibiofemoral
articulation
forms
a
hinge
joint
with
the
distal
femur
and
the
proximal
aspect
of
the
tibia.
The
distal
end
of
the
femur
includes
two
major
projections
known
as
the
medial
and
lateral
femoral
condyles.
The
intercondylar
notch
separates
the
joint
into
the
medial
and
lateral
compartments.
The
medial
condyle
is
positioned
more
anteriorly
and
has
a
larger
articulation
with
thicker
articular
cartilage,
while
the
lateral
condyle
is
bigger
in
shape.
These
large,
asymmetrical
condyles
articulate
with
the
relatively
flat
and
shallow
medial
and
lateral
tibial
condyles.
This
creates
an
incongruent
articulation
at
the
joint
that
is
mechanically
weak
and
lacks
overall
structural
stability.
Therefore,
the
surrounding
muscles
and
ligaments
are
crucial
for
providing
stabilization
at
the
joint.
Unlike
other
structures
in
the
lower
extremity,
these
surfaces
are
highly
unstable
in
effort
to
allow
a
large
range
of
motion
to
occur
at
the
joint.
Due
to
the
incongruent
surfaces,
much
of
the
stability
and
strength
of
the
knee
is
provided
less
by
bony
articulation
and
is
instead
provided
by
the
numerous
ligamentous
structures
and
the
muscles
and
tendons
acting
at
the
joint.
The
knee
joint
reaches
its
greatest
stability
in
a
position
of
full
extension
with
slight
external
rotation.
This
point
of
maximal
contact
and
congruency
is
the
close-­‐packed
position.
In
this
position,
the
ligaments
are
in
full
tension,
and
range
of
motion
is
limited
in
all
directions.
In
order
for
motion
to
occur
at
the
joint,
the
knee
must
be
in
some
degree
of
flexion.
The
joint
will
reach
its
greatest
amount
of
motion
in
25
degrees
of
flexion,
the
most
non-­‐congruent
position,
known
as
loose-­‐packed.
With
movement
into
flexion,
the
joint
will
rely
on
ligaments
and
tendons
to
provide
joint
stability.
Increasing
muscle
strength
also
provides
increased
stability
and
decreased
likeliness
of
injury.
In
order
to
achieve
maximal
articulation
at
this
incongruent
joint,
small
fibrocartilaginous
structures,
the
menisci,
are
attached
to
the
articular
surfaces
between
the
femoral
and
tibial
condyles
(Figure
9).
With
forces
at
the
tibiofemoral
joint
that
are
2-­‐4
times
the
amount
of
body
weight,
the
menisci
function
to
add
depth
to
this
shallow
Figure
8.
Tibiofemoral
joint

31. 31
articulation.
The
menisci
increase
the
surface
area,
shock
absorption,
and
stability,
while
decreasing
friction.
These
structures
also
function
to
provide
proprioception
at
the
joint
and
assist
with
accessory
motion.
The
lateral
meniscus
is
O-­‐shaped.
It
has
less
surface
area,
does
not
have
a
strong
attachment
to
the
tibia,
and
has
fewer
attaching
structures
than
the
medial
meniscus.
The
C-­‐shaped
medial
meniscus
attaches
to
the
anterior
cruciate
ligament,
posterior
cruciate
ligament,
medial
collateral
ligament,
and
the
semimembranosus.
With
stronger
attachments
to
the
tibial
plateau,
it
is
less
movable
within
the
joint,
placing
it
at
higher
risk
for
injury.
Table
2.
Joint
Motions
of
the
Tibiofemoral
Joint
Joint
Motion
Primary
Movers
Secondary
Movers
Knee
flexion
Hamstring
muscles:
Semimembranosus
Semitendinosus,
Long
head
of
biceps
femoris
Sartorius
Gracilis
Popliteus
Gastrocnemius
Plantaris
Knee
extension
Quadriceps
femoris:
Rectus
femoris
Vastus
lateralis
Vastus
intermedius,
Vastus
medialis
Tensor
fascia
latae
assists
in
maintaining
knee
extension
Internal
rotation
Semimembranosus
Semitendinosus
with
knee
flexed;
Popliteus
in
non-­‐weight
bearing
activity
with
knee
extended
Gracilis,
Sartorius
Popliteus
(in
non-­‐weight
bearing)
External
rotation
Biceps
femoris:
short
&
long
head
when
knee
is
flexed
Popliteus
(in
weight
bearing)
Biomechanics
of
the
Tibiofemoral
Joint
The
tibiofemoral
joint
is
a
shallow,
hinge
joint
with
two
degrees
of
freedom.
The
primary
motions
are
flexion
and
extension,
with
some
rotational
movement
occurring
in
knee
flexion
(Figure
10).
The
surrounding
tendons
and
ligaments
restrict
these
motions.
Muscles
are
referred
to
as
two
main
groups
acting
at
this
joint:
the
knee
Figure
9.
Menisci
of
the
knee
Figure
10.
Motions
of
the
knee