Abnormal Trunk
Behavior in Gait
David D. Wise, PT, Ph.D.
Normal Trunk movement in the
Sagittal plane
Up
And
Down
translation
Normal Trunk movement in the
Sagittal plane
Forward
Translation
Normal Trunk Behavior in Gait –
Sagittal Plane (Forward upward and
downward tranlation)
Forward
Backward
Downward
Upward
This illustration shows the pelvis translates up and
down in the sagittal plane (follow the dotted line). It
also twists R and L in the horizontal plane (follow
the R and L twists of the middle square). The pelvis
also tilts right and left and translates right and left
in the frontal plane but that is not seen well in this
illustration.
This illustration shows that the basic movement
of the pelvis in the sagittal plane is up and
down. The pelvis (and trunk atop it) reaches its
lowest point at loading response and reaches
its highest point at mid stance. Note that the
pelvis does not tilt significantly as it does in the
frontal plane.
To understand abnormal trunk movement during
gait imagine the trunk as an egg sitting on a
platform. The platform is the pelvis shown below
(the middle square). An egg sitting on that platform
would undergo accelerations and deceleration in all
three planes, as indicated by the dotted line.
Sagittal plane acceleration and deceleration.
The pelvis is accelerated and decelerated by the
lower extremities. In push off to mid stance it is
decelerated because it is traveling upward.
After mid stance it gains velocity because it is
dropping. At initial contact there is an abrupt
deceleration of the pelvis.
Normal Trunk movement in the
Sagittal plane
Trunk tilts
or leans
are
always
Abnormal in
the
Sagittal
Plane
Normal Trunk Behavior in Gait –
Frontal Plane (Right and Left with up and
down tranlation)
Downward
Left
Right
Upward
Here is a frontal
view that
illustrates the
pelvic
translation in
the frontal
plane. The
pelvis
translates
toward the mid
stance side
with each gait
cycle.
R mid stance
L mid stance
R mid stance
L mid stance
If an egg were sitting
atop the pelvis it
would be accelerated
and decelerated R
and L with each step.
An acceleration of the
pelvis to the left
should make the egg
roll in to the R. A
deceleration of a right
moving pelvis should
make the egg continue
to roll to the R.
R mid stance
L mid stance
R mid stance
L mid stance
The dotted line shows the pelvis translates up and
down in the sagittal plane. An egg sitting on the
platform would translate up and down with the
pelvis. The pelvic translations and twists right and
left in the horizontal plane. It also tilts right and left
and translates right and left in the frontal plane but
that is not seen well in this illustration.
Normal Trunk movement in the
Frontal plane
Trunk tilts
or leans
are
usually
Abnormal in
the
Frontal
Plane
This illustration better shows the tilts and
translations of in the frontal plane during normal
gait. Illustration a shows that in L midstance the
pelvis tilts to the R. Illustration b shows the same as
the previous slide (translation of the pelvis toward
the mid stance side.)
When the pelvis tilts in mid stance an egg sitting on
it would roll in the direction of the tilt. When the
pelvis is accelerated (Acc.) going into mid stance
the egg should roll opposite the direction of
acceleration. At the end of mid stance the pelvis is
decelerated (Dec.) and the egg should continue to
roll in the direction in which it was originally moving.
When the pelvis tilts in mid stance partial
compensation (upper occurs). The same occurs for
the lateral acceleration and deceleration. .
When the platform rotates, the egg wants to “go along for the
ride” and rotate in the same direction. If this actually occurred
when we stepped forward with the right leg we would always be
looking to the right and when stepping forward with the left we
would always be looking to the left. Click once to see this
effect.
A = Left
B = Right
In gait only the bottom of the trunk (egg) rotates in the same
direction as the pelvis(platform). The upper trunk (head, arms
and shoulders rotate opposite the pelvis. For this reason an
arm swings forward and backward with the opposite lower
extremity. Click once to see this effect.
A = Left
B = Right
Lower trunk
Upper trunk
Tilts are the most common
abnormal trunk movement
Tilt
Forward or
Backward
Left or Right
Why do tilts occur?The trunk can be compared to an egg
sitting on a platform (the pelvis). If the platform tilts to
the left or anterior, the egg tends to roll to the left or
anterior. The center of gravity shifts to the left or
anterior. There is greater demand on the right or posterior
control structures. Click once to see this effect.
Left or
Anterior
Right or
Posterior
Tilts can be caused by acceleration. If the the platform is
accelerated to the right or posterior, the egg tends to roll
to the left or anterior. The center of gravity shifts to the
left or anterior. There is greater demand on the right or
posterior control structures. Click once to see this
effect.
Left or
Anterior
Right or
Posterior
Tilts can be caused by deceleration. If the platform is
decelerated on the right or posterior, the egg will tend to
roll toward the right or posterior. The center and line of
gravity shifts to the right or posterior. There is greater
demand on the left controllers. Click once to see this
effect.
Left or
Anterior
Right or
Posterior
Decelerator
Compensatory
Trunk
Behavior
Compensation for platform tilt. If the right controlling
structures have “prior knowledge” that the platform will
be tilting to the left or anterior, the egg can be prepositioned to the right or posterior. The center of gravity
is pre-positioned to the right or posterior before tilt. The
result is that the center of gravity ends up in the middle of
both egg and platform. Click once to see this effect.
Left or
Anterior
Right or
Posterior
Compensation for platform acceleration. If the controlling
structures have “prior knowledge” that the platform will
be accelerated to the right or posterior, they can preposition the egg into a right or posterior tilted position.
When acceleration occurs the center of gravity of both
the egg and platform end up the center again. Click once
to see this effect.
Left or
Anterior
Right or
Posterior
Compensation for platform deceleration. If the controlling
structures have “prior knowledge” that the platform will
be decelerated on the right or posterior, the left
controllers can pre-position the egg into a left or anterior
tilted position just before deceleration. When
deceleration occurs the center of gravity of both the egg
and platform will be in the center again. Click once to see
this effect.
Left or
Anterior
Right or
Posterior
Decelerator
So far I have illustrated the trunk as a single unit
sitting on a platform (pelvis). The trunk is actually
more like two eggs balance atop each other. Each
has its own C of G allowing more sophisticated
compensation.
Fully Uncompensated (for the
position of the platform).
Trunk
segment
C of G
Both upper trunk
and lower trunk
lean in a direction
imposed by the
platform.
Total
C of G
Fully Compensated (for the
position of the platform).
Trunk
segment
C of G
Both upper trunk
and lower trunk
lean in a direction
opposite that
imposed by the
platform.
Total
C of G
Partial Compensation (Upper)
(for the position of the platform).
Trunk
segment
C of G
Total
C of G
Lower trunk in the same
direction as imposed
by the platform;
upper trunk leaned
opposite direction
imposed by platform
Causes a change in
shape of the trunk
(lordosis; kyphosis;
scoliosis)
Most common
Partial Compensation (Lower)
(for the position of the platform).
Trunk
segment
C of G
Total
C of G
Lower trunk in a
direction opposite
that imposed by the
platform; upper trunk
leaned same
direction imposed by
platform
Causes a change in
shape of the trunk
(lordosis; kyphosis;
scoliosis)
Much less common
Fully Uncompensated,
Fully Compensated,
Partial compensated (upper)
and
Partial compensated (lower) can all
occur with platform acceleration and
deceleration.
Examples – R. Hip Abductor weakness in R. Mid-Stance
(Compensated or Uncompensated for Pelvic Position.)
Fully Uncompensated
for pelvic position
Partial Compensation – Upper for
pelvic position
Description of Compensation/
Uncompesated
• When describing a mechanical behavior as
compensatory or uncompensated be sure
to state what condition compensation or
uncompensated is for.
–
–
–
–
Could be for pelvic position
Could be for muscle weakness
Could be for tissue tightness
Could be for balance and equilibrium
Compensation/Uncompensated
• So far the illustrations have shown
compensations for the position of the upper and
lower trunk on a platform. This has been done to
introduce the concept of uncompensated and
compensated behavior. Trunk behavior is almost
never related to only the position of the platform
or pelvis. Most often compensatory or
uncompensatory behavior is related to muscle
strength, tissue length in the lower extremities or
generalized balance/equilibrium problems.
Compensation/Uncompensated
• Compensatory behavior is related to the
demands imposed on the body by carrying
the trunk on the extremities. The main
demands are:
• muscle strength/endurance
• length of muscle and joint tissues
• Connective tissue strength (ligaments,
cartilage, bone)
• Neurological control, particularly of
muscles coordination, balance and
equilibrium.
Compensation/Uncompensated
• Each sub-phase has the same basic
demands, i.e., some form of muscle
strength, tissue length and neuro
control required but the muscle from
which strength is required, tissues
that require lengthening and exact
neuro demands differ in structure and
intensity.
Compensation/Uncompensated
• Definition of uncompensated behavior
– Abnormal behavior (trunk tilt, lurch,
abnormal shape) occurs in the subphase of demand.
– What should occur if the demand is not
met actually occurs.
Compensation/Uncompensated
• Definition of compensatory behavior
– Abnormal behavior (trunk tilt, lurch,
abnormal shape) occurs in a sub-phase
prior to the sub-phase of demand.
– What should occur if the demand is not
met is avoided.
Un-compensate vs.
Compensatory behavior:
Example – Quad Weakness
Normal quad –
meets demand for
keeping knee
extended at IC
Weak quad –
uncompensated behavior;
knee buckles; posterior
lurch or lean
Weak quad – compensatory
behavior; in TSw pt lurches
forward so C of G is in front of
knee decreasing demand on
quad; anterior lurch or lean
Un-compensate vs.
Compensatory behavior:
Example – Quad Weakness
Normal quad –
meets demand for
keeping knee
extended at IC
Fully Uncompensated;
both lower trunk and
upper trunk backward
Fully compensatory – both lower
trunk and upper trunk forward.
Un-compensate vs. Compensatory behavior:
Example – Quad Weakness; Variations (fully
compensated and fully compensated are shown on the
previous slide].
Weak quad - Partial compensation
upper – slight weakness;
“grandpa” walk; crouched gait
Weak quad – partial compensation lower –
moderate weakness – causes lordosis
Un-compensated vs. Compensatory
behavior: Example – Posterior ankle
tightness
Normal length post
structures meet
demand for
elongation at TSt to
allow dorsiflexion.
Uncompensated - Tight
posterior ankle structures
do not allow dorsiflexion;
pt falls backward –
posterior lurch or lean
Compensatory – trunk is lurched
forward to maintain forward
momentum; gets better step
length.
Un-compensated vs. Compensatory
behavior: Example – Posterior ankle
tightness (Variations)
Normal length post
structures meet
demand for
elongation at TSt to
allow dorsiflexion.
Fully Uncompensated –
What would occur if there
is no attempt to
compensate
Fully Compensatory – Both upper
and lower trunk forward
Un-compensated vs. Compensatory
behavior: Example – Posterior ankle
tightness (Variations)
Partial compensation upper –
Note hyperextension of knee (pt
with gastroc tightness could not
do this.
Partial compensation lower – Lower trunk
and pelvis forward; upper back; note
hyperlordosis of trunk.
Un-compensate vs. Compensatory behavior:
Example – Hip Abductor weakness
Normal Hip Abd–
meets demand for
keeping pelvis
from dropping
away in Mid stance
Weak Hip Abd –
uncompensated behavior;
knee buckles; lateral
lurch or lean away
Weak quad – compensatory
behavior; in TSw pt lurches
forward so C of G is in front of
knee decreasing demand on
quad; anterior lurch or lean
Un-compensate vs. Compensatory behavior:
Hip Abductor weakness (Variations)
Partial compensation – upper;
scoliosis of the spine
Weak quad – compensatory
behavior; in TSw pt lurches
forward so C of G is in front of
knee decreasing demand on
quad; anterior lurch or lean
Un-compensate vs. Compensatory behavior:
Example – Hip Adductor tightness
Normal
step width
Normal Hip Add–
meets demand for
length necessary
eeping pelvis from
dropping away in
Mid stance
Tight hip adductor –
uncompensated behavior;
knee buckles; lateral
lurch or lean away
Narrow
step
width
Tight add – compensatory
behavior; affected leg in greater
adduction;shortens leg; pt falls
more to affected side.
Un-compensate vs. Compensatory behavior:
Example – Hip Adductor tightness
Normal
step width
Tight hip adductor –
partial compensated
upper
Narrow
step
width
Tight add – Partial compensatory
upper for sharp fall to affected
(functionally short side)
Un-compensate vs. Compensatory behavior:
Hip Abductor weakness (Variations)
Partial compensation – upper;
scoliosis of the spine
Weak quad – compensatory
behavior; in TSw pt lurches
forward so C of G is in front of
knee decreasing demand on
quad; anterior lurch or lean
Compensation for What?
• Interpreting trunk behavior as either
compensatory or uncompensatory
takes prior knowledge of the specific
demands of each sub-phase of gait.
Uncompensated behavior
• If the consequences of not meeting
the demand ( not compensating for a
deficit) would not result in pain, loss of
balance or falling, dys-equilibrium,
tissue damage, loss of dignity, or
severe cardio-respiratory demands,
the patient will probably exhibit the
un-compensated behavior.
Compensatory behavior
• If the consequences of not meeting
the demand ( not compensating for a
deficit) would result in pain, loss of
balance or falling, dys-equilibrium,
tissue damage, loss of dignity, or
severe cardio-respiratory demands,
the patient will probably exhibit the
compensatory behavior.
Arm Swing- There are basically
two types (at least in the sagittal and frontal
planes)
• Passive arm swing
– Occurs as a result of trunk tilt
– Arm swing in same direction as trunk
– Arm swings loosely
• Active arm swing
– Helps retard C of G movement in direction of trunk tilt
– Arm swing in opposite direction from trunk movement
– Arm is usually more rigid
Arm Swing
• Passive Arm Swing
• Happens as a result
of tilt of the trunk
• Does not help with
control of C of G
• A helpful
observation that
marks trunk tilt
Arm Swing
• Active Arm Swing
Compensation in the horizontal
plane
• One side girdle goes with another
• If there is diminished shoulder girdle
movement on the L there will be diminished
pelvic movement on the R.
• If there is excessive shoulder girdle
movement on the L there will be excessive
pelvic movement on the R.
Abnormal trunk movement during gait
(assuming the neuro-motor system is
normal) is the behavior seen when the
trunk tries to deal with abnormal
accelerations and decelerations
imparted to the pelvis (platform) by the
lower extremities.