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) Upward Forward Backward Downward

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) Upward Left Right Downward

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. L mid stance R mid stance L mid stance R 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. L mid stance R mid stance L mid stance R 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 Upper trunk Lower 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. Decelerator Left or Anterior Right or Posterior

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 pre- positioned 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 pre- position 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. Decelerator Left or Anterior Right or Posterior

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). Both upper trunk and lower trunk lean in a direction imposed by the platform. Total C of G Trunk segment C of G

Fully Compensated (for the position of the platform). Both upper trunk and lower trunk lean in a direction opposite that imposed by the platform. Total C of G Trunk segment C of G

Partial Compensation (Upper) (for the position of the platform). 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 Total C of G Trunk segment C of G

Partial Compensation (Lower) (for the position of the platform). 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 Total C of G Trunk segment C of G

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 sub- phase 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 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 Normal Hip Abd– meets demand for keeping pelvis from dropping away in Mid stance

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 Tight hip adductor – uncompensated behavior; knee buckles; lateral lurch or lean away Tight add – compensatory behavior; affected leg in greater adduction;shortens leg; pt falls more to affected side. Normal Hip Add– meets demand for length necessary eeping pelvis from dropping away in Mid stance Normal step width Narrow step width

Un-compensate vs. Compensatory behavior: Example – Hip Adductor tightness Tight hip adductor – partial compensated upper Tight add – Partial compensatory upper for sharp fall to affected (functionally short side) Normal step width Narrow step width

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.