gait phases kinetics kinema tics

8/10/2019 Gait Phases Kinetics Kinema Tics

1/36

Kinesiology Gait I: PHASES OF GAIT

Gait I: Overview, Overall Measures, and Phases of Gait

Overview of biomechanics

Temporal and spatial measures Phases of gait

Determinants of gait

Functional tasks during gait and the three rockers

Overview of Biomechanics

Of all human movements, walking has by far received the most study. What we learn from

biomechanical analyses of walking provides a framework for studying all kinds of movements, such asreaching and grasping, sucking, mastication and swallowing, and movements of the eyes. Even for those

clinicians who will not directly treat gait deviations, an understanding of gait biomechanics and a familiaritywith normal gait will provide a quick window into the patients level of function because gait is such a

common and readily observable activity that involves so much of the body.

Temporal and Spatial Measures

Temporal and spatial measures examine global aspects of gait. Because gait is a cyclical activity, thebasic assumption is that one step is essentially the same as the next. Thus, a parameter such as stride length

is expected to be characteristic of the persons overall walking performance, not just the step(s) measured.The sections in Joint Structure and Function provide good descriptions of the basic temporal and spatial

measures of gait. The following list serves as a repository for notes and definitions.

Stride Duration (cycle duration, cycle period)

Stance Time (stance duration)

Swing Time (swing duration)

Single Support Time

Double Support Time

Stride Length

Step Length

Base of Support Width

Degree of Toe Out

Cadence

Velocity


2/36


Phases of Gait

Gait, particularly walking, is a cyclic phenomenon that can be divided into segments, or phases. Two

sets of terminology are currently in use: the traditional terminologyand theRancho Los Amigos(RLA)

system. The traditional terminology developed as interest in gait rehabilitation mounted after WWII in theeffort to improve lower extremity prosthetics. It describes gait in terms of discreet, momentary events, such

as heelstrike, heel rise, and toe-off. TheRancho Los Amigos(RLA) terminology became increasingly

popular in the late 1980s and early 1990s and is currently assuming a position as the preferred standardamong clinicians. It describes gait more in terms of processes or segments of time, such as loadingresponse, terminal stance, and pre-swing, and because it is semantically more generic and better

encompasses the common features of normal and pathological gait. T traditional terminology uses the termheel strike where the RLA system uses the term initial contact to refer to the instant when the limb

contacts the ground. Initial contact applies equally well to the gait of a child with cerebral palsy whoactually makes contact with the toes as it does to the gait of a person with an amputated lower extremity or a

person without disability who makes contact with the heel. In communicating with your colleagues andto understand the published literature, however, you will need to be fluent in both nomenclatures. The

section inJoint Structure and Functiondoes an excellent job of comparing the nomenclatures, and ofcourse, the source of the RLA terminology is the Observational Gait Analysisbook. Please study these

sources (pg. 5 in Obs. Gait Anal.and pp. 450-456 inN & L).

While the phases of gait defined in the RLA terminology are fine for walking, which is usually the focus

of medical rehabilitation, additional nomenclature applies when studying running, which may be importantin a sports-related, orthopedic practice. For both walking and running, stance gets much shorter and swing

gets slightly shorter as speed increases. Thus, as speed increases, theproportionof the cycle devoted tostance decreases and the proportion of the cycle devoted to swing increases. For very fast sprinting, the

absolute duration of swing may actually begin to increase as extremely high speeds are reached.

The next ten plates are taken from a computer program, GAIT TUTORIAL, created by Roger Allen, Mark

Guthrie, and John Buford. (Gait Tutorial was created on Macintosh HyperCard, a program that almost no onehas anymore). The plates provide graphic and written descriptions of the RLA phases of gait. Please also

study the corresponding sections in Observational Gait Analysis, and Norkin & Levangie or Oatis.


3/36



4/36



5/36



6/36



7/36



8/36


Determinants of Gait

The determinants of gait are a group of 5 features of an individuals gait that interact dynamically togovern the vertical and horizontal displacement of the center of mass, and hence, profoundly influence

efficiency. Consult Joint Structure and Function along with the following descriptions.

LATERAL PELVIC TILT IN THE FRONTAL PLANE.A controlled, intended pelvic drop ipsilateral to the swinging limb during the time of single limb support.The pelvic drop is maximal at the time when the center of mass (COM) reaches its maximal vertical extent.

Hip abductors on the side of the stance limb contract eccentrically to allow the intended extent of controlledpelvic drop. The primary function of lateral pelvic tilt, also known as pelvic obliquity, is to control the

vertical excursion of the COM.

KNEE FLEXION AT MIDSTANCE.

Complements lateral pelvic tilt. From the time of foot-flat until midstance, the knee joint actually flexes

under the load of the body. This acts as a buffer to reduce the inverted pendulum, vaulting effect thatwould be exaggerated if the knee were locked in extension throughout the gait cycle. Thus, the effective

length of the limb, the distance from the COM to the point of limb-ground contact, varies in a controlledfashion in order to control the vertical excursion of the COM.

KNEE, ANKLE, FOOT INTERACTIONS.

Act during the loading response (early in stance) and preswing (at the end of stance) to vary the effectivelength of the limb. They make the limbs longer than they would otherwise be so that the COM does not

fall quite so far before contact is achieved (or lost). While one limb hastens the onset of heel contact witha dorsiflexed ankle, the opposite limb delays the time of toe off with a plantarflexed ankle. These events

occur concurrent with the lowest vertical position and the maximal upward acceleration of the COM as its

descent ends and ascent begins during double support.

PELVIC ROTATION IN THE TRANSVERSE PLANE.

Mechanically coupled with the advancement of the limb during swing and the progression of limb duringstance. That is, as the right limb swings forward, the right side of the pelvis also moves forward so that the

pelvis rotates to the left. During stance for the right limb, the pelvis rotates to the right. Like the knee,ankle, foot interactions, pelvic rotation in the transverse plane prolongs stance by hastening the onset of heel

contact and delaying the time of toe off. This action extends the stride length and further modulateseffective limb length to limit the drop of the COM.

(PHYSIOLOGIC VALGUS OF THE KNEE - I DON'T LIKE THIS ONE)

Places the base of support more nearly under the COM to reduce the lateral shift of the base of support whentransferring weight from limb to limb. This limits the energy expended on translating the COM in the

frontal plane.


9/36


Functional Tasks during Gait and The Three Rockers

Three functional tasks during gait, Weight Acceptance, Single Limb Support, and Swing LimbAdvancement, are described in Observational Gait Analysis. Please study those descriptions.

Another set of concepts used by the Rancho Los Amigos team is referred to as The Three Rockers.

These concepts are presented in Dr. Perrys book entitled Gait Analysis. A brief summary is presented hereto provide some familiarity with these concepts.

HEEL ROCKER.

Lasts from initial contact to the time of foot flat. Its function is to translate the vertical component of the

ground reaction force into forward progression of the tibia through the link provided by the eccentric actionof tibialis anterior.

ANKLE ROCKER.

Lasts from the time of foot flat to heel rise. Its function is to control the rate of forward progression of thebody as the tibia rotates at the ankle joint over the fixed foot under the eccentric control of the triceps surae.

FOREFOOT ROCKER.

Lasts from heel rise until the end of stance. It functions to extend the period of ground contact via thegastrocnemius to exploit the GRF vectors helpful influence on swing initiation.

Study Exercises

1. Practice drawing the stick figures at the various phases of the gait cycle, labeling them with the phase ofgait and the percentage of the gait cycle at which the limb would assume that configuration.

2. Given the phase of the ipsilateral limb, be able to name the phase of the contralateral limb.

3.

List the determinants of gait along with their functions in controlling the COM. For each determinant,specify the RLA phase(s) of gait during which they operate.

4. Associate the three rockers with the functional tasks during gait.

5. Take a stop-watch and a tape measure and compare some of the spatio-temporal measures of gait forfriends and relatives of various sizes and ages.


10/36

Kinesiology Gait II: KINEMATICS

Gait II: JOINT KINEMATICS

Lower extremity kinematics

Ancillary motions

Lower Extremity Kinematics

Sagittal plane motions

Following this page are 36 plates are from the Gait Tutorial(Allen, Guthrie, & Buford) that provide

concise graphic and written descriptions of the sagittal plane motions at the hip, knee, and ankle). Refer toObservational Gait Analysisand Joint Structure and Function for more detail). Following those pages are

written descriptions of additional motions, such as motions in transverse and frontal planes.


11/36



12/36



13/36



14/36



15/36



16/36



17/36



18/36



19/36



20/36



21/36



22/36



23/36



24/36



25/36



26/36



27/36


HIP CURVE

KNEE CURVE


28/36


ANKLE CURVE

ALL CURVES


29/36


MTP joint in the sagittal plane

At initial contact, the MTP joint is at 25 of dorsiflexion. MTP plantarflexion begins immediately and

neutral is achieved by foot flat. During midstance, the MTP joint remains at neutral. MTP dorsiflexionbegins at heel rise during terminal stance, reaching 20 of dorsiflexion by the onset of preswing. By the end

of preswing, the MTP joint reaches its peak at 55 of dorsiflexion. During initial swing, the MTP jointreturns to neutral where it remains during midswing. During terminal swing, the MTP joint assumes a toe-

up (dorsiflexed) posture in preparation for initial contact.

Main non-sagittal plane motions

PELVIC ROTATION

The pattern of pelvic rotation is fairly symmetrical. The pelvis rotates externally from initial contact untilthe onset of preswing, the first 50% of the cycle, and internally during preswing and swing, the second 50%

(Note: External pelvic rotation means that if the stance limb were the right, the pelvis would be rotating tothe right as seen from above).

HIP INTERNAL AND EXTERNAL ROTATIONThe hip rotates 8 from neutral in a monotonic fashion (i.e., like a sine-wave, with one maximum and oneminimum). Peak internal rotation occurs during Pre-Swing, and peak external rotation occurs toward the

end of Loading Response. That is, rotation at the hip trails pelvic rotation slightly -- so at the end ofLoading Response the hip begins internally rotating and continues to do so until well into Pre-Swing when it

begins externally rotating (and does so until well into Loading Response).

HIP AB / AD DUCTION

The hip ab- and adducts 7 from neutral. During the loading response, the pelvis undergoes a controlleddrop on the contralateral side, thus the ipsilateral hip adducts under the eccentric control of gluteus medius

and minimus (remember the Determinants of Gait?). During midstance, the hip moves in the abductordirection, returning to neutral (level pelvis) by the onset of terminal stance and more or less remaining so

until the onset of preswing. Just the opposite occurs thereafter, with rapid abduction as the limb is unloadedduring preswing, etc. The bump, flat, dip, flat pattern characteristic of self-paced walking changes to a

more sinusoidal pattern during rapid walking and running.

SUBTALAR JOINT

The subtalar joints vary 5 from neutral in a roughly monotonic fashion. There is rapid eversion duringthe loading response, which slows greatly but continues into midstance. The subtalar joints begin re-

supinating during midstance, ideally returning to neutral during terminal stance. Peak inversion occurs

during preswing and the subtalar joints actually begin to return towards neutral before toe off. The return toneutral is completed during initial swing, and the subtalar joints hover near neutral for the remainder ofswing, often entering initial contact in slight inversion (thus contact on postero-lateral heel).

Ancillary Motions


30/36


Ancillary motions are mainly aimed at conservation of energy, shock absorption, and behavioral goals (e.g.,being able to look where you're going).

PELVIC TILT

Pelvic tilt is a sagittal plane motion akin to flexion and extension in the lower extremities. During walking,the position of the pelvis remains within a few degrees of 15 of anterior tilt. The pattern of pelvic tilt

motion is biphasic, with an excursion of 4 from the average position. Throughout most of swing theposterior tilt of the pelvis increases (you would say the pelvis is tilting posteriorly). Just before initial

contact this reverses and the pelvis begins tilting anteriorly. Then very early in midstance the pelvis beginstilting posteriorly (which makes sense since this is the beginning of swing phase on the contralateral side,

and as stated two sentences previously, throughout most of swing the posterior tilt of the pelvis increases).

PELVIC OBLIQUITY

Pelvic obliquity is analogous to ab- and adduction at the hip, and indeed, the patterns are so similar that the

description for hip ab-adduction can almost be substituted for pelvic obliquity. The basic feature of pelvicobliquity is that the pelvis is higher on the stance side than on the swing side. The orientation angle of the

pelvis in the frontal plane varies 4 from neutral, with the reference side highest relative to the opposite

side at the end of the loading response, and conversely, lowest at the onset of swing.

PELVIC ROTATION

The pattern of pelvic rotation is symmetrical. The pelvis rotates externally from initial contact until theonset of preswing, the first 50% of the cycle, and internally during preswing and swing, the second 50%.

The excursion is 10 from neutral. This basic pattern follows the advancement and retraction of the limbduring swing and stance.

TRUNK COUNTER-ROTATION AND RECIPROCAL ARM SWING.

When the reference hip girdle is forward for initial contact, the same shoulder girdle is positionedposteriorly. This preparatory posture helps offset the braking impulse created by sheer of the foot at

contact, which in driving the hip backward, tends to pitch the trunk forward. By having that side of thebody positioned posteriorly when contact is made, the body has room to allow for some pitch without letting

the COM get too far out in front of the supporting limbs. Reciprocal arm swing follows counter-rotation, sothat not only is that shoulder girdle positioned posteriorly, but the whole arm is hanging back. Thus,

while the reference extremity is moving forward, the ipsilateral arm and its shoulder girdle are movingbackward. While reciprocal arm swing is a conspicuous feature of normal gait and asymmetries in

reciprocal arm swing can be powerful indicators of gait deviations, that fact remains that a person withbilateral shoulder-disarticulating amputations will have little trouble walking.

HEAD-ON-BODY MOVEMENTS.

Slight head and neck rotation keep the face forward by canceling trunk counter-rotation. This keeps theeyes oriented towards the goal. During turning, head rotation will be offset to help maintain gaze fixation

on the target. Indeed, the eyes drive head position, and as long as the vertical orientation is not tooconfusing to your gravitational reference, you can look pretty much anywhere you want while walking.

Nonetheless, its still good to look where youre going.


31/36


SummaryMovements of all four limbs and of the head and trunk are coordinated during walking. There are detailed

kinematic measures in the literature for most joints and or segments you might need to research. The dataprovided here and in your texts should provide you with all you need for most practical situations.

Study Exercises

1. Set up a table with the following columns and fill in the data for the hip, knee, and ankle in the sagittal

plane:

Joint RLA phase Starting position Ending position Arc(s) of motion Peak(s) reached

hip terminal stance 5 flexion 10 extension 15 extension Peak extension @ 10

...

2. Learn to draw the hip, knee, and ankle-joint range of motion graphs for the sagittal plane from memory.

By memorizing the peaks and when they occur, you can learn to do this with surprising accuracy with arelatively short list of numbers in your head and a general image of how the plots should look.

3. Describe hip ab/adduction, int/external rotation, MTP dorsi/plantarflexion, and subtalar in/eversion in

terms of the operating ranges of motion associated with normal function, i.e.,the peak positions, and thetimes when those peaks occur.

4. Describe the coordination of head, trunk, and arm motion for normal walking.

5. Describe the major kinematic events associated with the following functional tasks during gait:Weight Acceptance

Single Limb SupportWeight Transfer (Contralateral Weight Acceptance)

Limb Advancement

6. Take the Obs. Gait Anal.book and find a place where you can watch a lot of people walk by. Study the

graphs and learn to recognize how they illustrate the movements you see during normal walking.


32/36

Kinesiology Gait III: KINETICS

Gait III: KINETICS

INTRODUCTION (read for background)

JOINT TORQUES (MOMENTS).

The torque is the effort devoted to changing the rotational velocity of segments. The net torque is the finalsum of four factors that contribute to torque production at the joint:

!"=!External+!Gravitational+!Intersegmental+!Muscle

The external torquein normal walking results from the reaction of the ground with the foot, known asthe ground reaction force (GRF).

Thegravitational torqueacts at the center of mass due to the gravitational field. For example, interminal swing, the gravitational torque tends to flex the knee. In space-walking, gravitational torques

would be negligible.

The intersegmental torqueresults from the angular accelerations and angular velocities of other

segments in the system. For example, during initial swing, the angular velocity of the thigh creates acentripetal force that tends to extend the knee, while at the same time, the angular acceleration of the leg

tends to cause knee flexion. Why is this so? The mass of the shank and foot distal to the knee wants to flyoff into space due to the angular velocity of the thigh. Even the most experienced investigators find that

intersegmental dynamics are so interactive and so complex that they defy intuition there is no way toguess only a full blown biomechanical analysis can reveal the intersegmental dynamics. The

intersegmental torque is often called the motion dependent torque or the inertial torque.

The muscle torqueresults from the combined action of all musculoskeletal elements acting at the joint

and is calculated as a residual term. That is, in equation 3.2 above, !", !External, !Gravitational, and !Intersegmental

can all be calculated (i.e., estimated) from the dynamic analysis. The muscle torque is then calculated as

the residual in the following equation:

!Muscle= !"- (!External+!Gravitational+!Intersegmental)

As you may have guessed, from this perspective the muscle torque consists of not only the torques created

by active contraction of muscles acting around the joints, but also includes torque due to forces inperiarticular structures such as passive muscles, ligaments, and periarticular soft tissue deformation.

Further, to the extent that errors in the estimation of net torque are independent of errors in the estimation ofexternal, gravitational, and intersegmental torques, the muscle torque will include any differences in

measurement errors for the net torque vs.the other three components in equation 3.3.

Lower Extremity Kinetics

Following this page are eight plates from the Gait Tutorialthat provide graphic and written descriptionsof muscular activity during sagittal plane motions at the hip, knee, and ankle). Refer to Observational Gait

Analysisand Joint Structure and Function for more detail). Following those ten pages are writtendescriptions of additional motions, such as motions in transverse and frontal planes.


33/36



34/36



35/36



36/36


gait phases kinetics kinema tics

Documents