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3 1293 00891 7225

This is to. certify that the

thesis entitled

Effects of Semi-Rigid Orthotics on
Abduction-Adduction Moments at the Knee
Joint During Walking.

presented by

Renee A. Peltier

has been accepted towards fulfillment
of the requirements for

Mvo degree in the SChOOl Of
Health Education, Counseling
Psychology and Human Performance

 

 

0le (W

Major professor

 

Date /l(M/v 92?, /?§0

0-7639 MS U i: an Affirmative Action/Equal Opportunity Institution

 

 

LIBRARY
Mlchlgan State
Unlverslty

 

 

PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINES return on or before date due.

DATE DUE DATE DUE DATE DUE

 

 

 

 

 

 

 

 

 

 

EFFECTS OF SEMI-RIGID ORTHOTICS ON
ABDUCTION-ADDUCTION HOHENTS AT THE KNEE
JOINT DURING WALKING

By

Renee A. Peltier

THESIS

Submitted to
Hichigan State University
in partial fulfillment of the requirements
for the degree of
MASTER OF ARTS

Department of Health Education. Counseling Psychology,
and Human Performance

1990

 

6¢7 — 533$

ABSTRACT

EFFECTS OF SEHI-RIGID ORTHOTICS 0N
ABDUCTION-ADDUCTION HDHENTS AT THE KNEE DURING WALKING

By

Renee A. Peltier

The purpose of this study was to examine the effects
of semi-rigid orthotics on the abduction-adduction moment
acting at the knee joint during the stance phase of
walking. A three-dimensional gait analysis of five

subjects walking under two conditions. shoe alone and shoe

plus orthotic was performed. The orthotics used were
prescribed to control excessive pronation. Kinematic data
were collected using two LOCAH high speed cameras. An

AHTI force platform was used to simultaneously collect the
ground reaction forces and moments about the platform
center. The approach taken in this study utilized the
concepts of rigid body dynamics and the Newton-Euler
equations of motion. The abduction-adduction moment
acting at the right knee was calculated from the three-
dimensional kinematic and kinetic data. The abduction-

adduction moments at the knee were analyzed for general

 

patterns and trends.

The results were highly reproducible among subjects.
Analysis of the results revealed noticeable differences in
the abduction-adduction moment between the two
conditions. Comparison of the magnitudes shown by the
abduction-adduction moment between the two test conditions
revealed that the adduction moment was decreased in the
condition with the orthotic. The methods used in this
study allowed an objective analysis of the effects of

orthotics on knee Joint mechanics.

 

Dedication

To my Mother
Ann M. Peltier

iv

 

ACKNOWLEDGHENTS

I wish to express my appreciation to Dr. Dianne
Ulibarri for her guidance and advice. I wish to thank Dr.
nary Verstraete for her assistance with the data post-
processing procedures. Appreciation should also be
extended to Brook Shoes. Inc., whom supported this study
in part by a grant and to Ken Scholton and Hhairi
Blacklock of Gary Nederveld & Associates. whom provided
flexibility in my work schedule enabling me to complete
this study.

I wish also to express my sincere appreciation
to my family and to the following friends: Becky Stewart
for her unrelenting support and encouragement. Therese
Bednowicz for her patience. and to Maris Walters and Sue

Schryber for being there when I needed motivation.

 

 

TABLE OF CONTENTS

LIST OF TABLES. a a a s a o I o a a a e a a e o a a o a a a a o I a 0 a I a a I e o e e a a a o o 11
LIST OF FIGURES........................................iii
INTRODUCTION. 0 o a o I a a a o o a a o a a e o a o a a a a o a a e o o I a o a a o a a a a o o o a a 1

I. NEED FOR THE STUDY............................ 5
II. PURPOSE OF THE STUDY...........................7
III. RESEARCH PLAN..................................8
IV. ASSUHPTIONS AND LIMITATIONS....................8
V. SIGNIFICANCE OF THE STUDY......................9
VI. DEFINITIONS...................................10

REVIEW OFLITERATUREIIIIOIIOCOI.DOC...COCO-IOOQDOIICCICU11
I. GAIT ANALYSISIIIOIICOIIODOIIIOOIIOIOOOOIIOOIOOI11

A. KINEnATIC STUDIESOOOOIOOI.OOOIIUODOOIIIOCIDIC12
B. FOOT-GROUND REACTION FORCE AND PRESSURE......14
C. JOINT AND HUSCLE FORCE ANALYSIS..............17

II. ORTHOTIC THERAPYaoooanan-Iaaaaaaaoeooooaoooaoo-le
HETHODSI-oaaaoaaooeaoolana.asaeleoaeoloaaooooaaoeao24

I. DATA COLLECTION PROCEDURES....................25
II. ANALYTICAL HETHODSIOIII...DOOOOCOIIIIOIIODCIICZ7

RESULTS AND DISCUSSION ..... .............................34

I. CONDITION I: WALKING WITHOUT ORTHOTIC.........35
II. CONDITION II: WALKING WITH ORTHOTIC...........37
III. DISCUSSION AND COHPARATIVE ANALYSIS...........4O

CONCLUSIONS.............................................47
APPENDIXooeeeanalogue-no...-Innocence-onloao-Io-ooaoneoosz
LIST OF REFERENCES. I e a a n a o a o o a a o a I I I o a o o o a o a a o a a a a a a o a o a 53

vi

 

Table 1.

Table 2.

Table 3.

LIST OF TABLES

Hean Values of the Abduction-Adduction
Homent Without 0rthotic......................35

Mean Values of the Abduction-Adduction
moment"1thorth°t1Cooooooooo-ooooooooooooo-a4o

Differences in Hean Peak Values of the
Abduction-Adduction Homent Across
Conditions...................................44

 

Figure

Figure

Figure

Figure

Figure

Figure

Figure

 

LIST OF FIGURES

Force Plate Coordinate Axis and the
Ground Reactions.........................

Schematic Representations of the Shank...

Abduction-Adduction Homent acting at the
Knee Walking Without an 0rthotic.........

Abduction-Adduction Moment acting at the
Knee Walking With an Orthctic............

Subject 1 Abduction—Adduction Homent
Across Conditions..... ..... ..............

Subject 2 Abduction-Adduction Homent
Across Conditions........................

Subject 4 Abduction-Adduction Moment
Across Conditions........................

viii

0.29

5.30

ll‘a

..45

INTRODUCTION

There are approximately 30 to 40 million people jogging
or running in the United States today (Krakauer. 1987).
Despite the great advances in the manufacture and design

of running shoes. the average runner will have one or two

injuries per year. due mostly to an unbalanced foot
structurE. overuse. or a combination of these two
conditions (Subotnick 1980). Although a number of

anatomical factors must be considered in the diagnosis and
evaluation of lower extremity problems encountered by
runners. it seems that many of these problems are related.
either directly or indirectly, to foot structure and
function during the support phase of the activity (Bates.
Osternig. Hason. & James. 1979). The most common
unbalanced foot structure is the flat (pronated) foot.
which results in an abnormal amount of subtalar joint
pronation during some component of the stance phase of
gait. There are many disorders associated with abnormal
pronation including heel spurs. planter fasciitis. shin
splints. chondromalacia patellae. excessive leg fatigue
and low back pain (HcPoil & Brocato, 1985). All these
disorders may be compounded with overuse and the

additional stresses of sport activities.

2

An overuse injury itself can result as a reaction of
the tissue to stress from the excessive motion. According
to a survey conducted by Eggold (1981). the most common
overuse injuries resulting from abnormal function of the
foot were chondromalacia patellae. shin splints. plantar
fasciitis. and Achilles tendinitis. He discussed the use
of orthotics in treating the abnormal structure of the
foot responsible for these symptoms. Eggold concluded
that orthotic control can have significant therapeutic
value in treating these conditions. The use of orthotics
has become popular as a means of preventing and treating
the stress related injuries found in long distance
running.

Knee pain was the major complaint among the runners
studied by several investigators (Newell & Bramwell. 1984:
Pretorius. Noakes, Irving. & Allerton, 1986; Bates &
Osternig. 1978; Clancy. 1980; Buchbinder. Napora. & Biggs.
1979; Blake & Danton. 1985). and many' of these runners
were able to return to their running activities pain-free
with foot orthotics. Thus. it would appear that orthotics
may effectively alter the mechanics of the knee joint
during gait. However, the majority of the work in the
area of orthotic therapy has focused on the subtalar
joint. not the knee joint. A study conducted by Burkett.
Kohrt. and Buchbinder (1985). investigated the effects of
orthotics on frontal plane knee kinematics during the

support phase of running. Results of this study were

inconclusive.

A biomechanical or functional orthotic device is
frequently prescribed by clinicians in treating lower
extremity problems. Newell and Bramwell (1984) reported
that in JJ. months. 50 percent of their athletic patient
population had knee pain complaints. Orthoses were
prescribed for 82 percent of these patients. The cost of
a pair of custom made orthotic appliances is between $200
and 9350. not including the physicians' office visit fees
(Krakauer. 1987). When one considers the frequency and
cost of orthotics one would expect to find a large number
of scientific studies supporting the effectiveness of
orthotics. However. this is not the case. In fact. there
are many in the medical community who remain skeptical and
some who suggest that orthotics may not only be
ineffective. but possibly harmful (Krakauer. 1987). There
are many different foot orthotics on the market today
Claiming to relieve pain and enhance foot function.
Unfortunately. minimal research has been conducted
investigating the effectiveness of orthotics in the adult
population. The effects of the orthotic device remain
poorly understood.

The role of the biomechanical orthotic is to control
excessive and potentially harmful subtalar and midtarsal
joint movement during the stance phase of gait (D'Ambrosia
& Drez. 1989). Therefore. research in the area of

orthotic therapy has focused on the effects of orthotics

4
in controlling subtalar joint motion. To date. research
performed on the effects of orthotics has been primarily
kinematic investigations of the foot in which inconsistent
findings have been reported.

More important is that during the stance phase of
gait the lower extremity functions in a closed kinetic
chain. i.e. all of the forces and moments are transmitted
through a .fixed end segment (the foot) cephally through
the lower extremity. Consider that the lower extremity
consists of three segments which are successively united
by joints. Since during the stance phase of locomotion.
the foot may be considered to be fixed distally. the shank

and the thigh above will alter their function in response

to the foot’s requirements. It is logical to assume that
any deviation of the foot from normal function would
affect the more proximal joints. In the case of an

unbalanced foot, misdirected forces and moments could
cause the lower extremity to compensate in some manner.
The resultant symptoms caused by compensation of the lower
extremity could vary widely, but it is felt that the most
common symptoms are related to the knee joint (Tiberio.
1987).

To date. the few kinetic investigations of orthotics
which have been performed. have focused on center of
pressure patterns. A center of pressure pattern is a
graphic representation of the location and magnitudeI of

the resultant force system between the foot and the force

5

Plate (Soutas-Little. Beavis. Verstraete. & flarkus
1987). Clearly. the position of the foot and the
resulting direction of the forces and moments acting at
the foot affects the gait pattern of the entire lower
extremity. Center of pressure information is critical to
an understanding of the mechanics of gait. Since accurate
assessment of foot motion inside a shoe is difficult. the
center of pressure is primarily used for studying the
effects of conditions involving plantar type pain on the
progression of forces along the foot during the stance
Phase of gait. At this present. time there have been no

reported investigations into the effects of orthotic
devices on the forces and moments acting at the joints of

the lower extremity which originate from the ground
reaction force system.

In the case of the structurally unbalanced foot. the
direction of the resultant forces and moments may be
detrimental to proper mechanics in the joints of the lower
extremity. namely the knee. Thus. an orthotic device
which was designed to balance the foot would also change
the direction and the effects of the resultant forces and
moments. By changing the direction of the resultant
forces and moments on the lower extremity. the detrimental
stresses would be reduced.

I. NEED FOR THE STUDY
Experiments directed at the analysis of the effects

of orthotics on the forces and moments acting on the knee

6

joint and in the surrounding connective tissue are
lacking. The forces and moments acting at the knee joint
which would most likely be affected by orthotics are those
acting in the medial or lateral directions in the frontal
plane. According to Morrison (1970). moments of
abduction or adduction acting on the knee joint are
resisted by the collateral ligaments. Abnormally large
moments of abduction or adduction may be responsible for
the clinical symptoms of knee pain which are effectively
treated by the use of orthotics. It may be possible that
if an individual were to continue their knee pain
producing activity, over a long enough period of time
without any treatment. abnormal knee joint motion might
occur. Abnormal knee joint motion would be present at the
end stages of pathology as a result of the cumulative
trauma effects of misdirected or abnormally large
abduction-adduction moments. Once there is measurable
abnormal knee joint motion the damage to the restraining
structures has occurred and orthotics would not be an
effective treatment.

Presently. there has been limited research performed
on the effects of orthotic devices on the forces and
moments at the knee joint. Consider the frequency of
orthotic therapy: the incidence of knee injury has been
reported to range from 29 to more than 50 percent in the
30 to 40 million Americans who run (Krakauer. 1987) and

nearly 80 percent of the runners who complained of knee

 

7
pain were eventually treated with orthotics (Newell &
Bramwell. 1984). Furthermore. orthotic therapy is
becoming more prevalent in sports other than running and
even nonsport related rehabilitation programs.

Considering the paucity of kinetic investigations on
the effects of orthotics. it appears that orthotic devices
are poorly understood. This lack of kinetic information
may be a contributing factor to inappropriate and
excessive prescription of orthotic devices. Consequently.
investigation of the effects of orthotics on the resulting
forces and moments of the lower extremity during the
stance phase of gait needs to be performed. This study
investigated the effects of orthotics on the abduction-
adduction moment acting at the knee joint during the
support phase of walking gait.

II. PURPOSE OF THE STUDY

The interdependency of foot function and knee
function have been well established (Buchbinder. Napora. &
31998. 1979). Certain changes in foot structure. and thus
its resulting function, cause changes in knee joint
function. Therefore. the purpose of this study was to
perform a three dimensional investigation to examine the
effects of a clinically prescribed. semirigid. orthotic on
the abduction-adduction moment at the knee during the

stance phase of walking.

III. RESEARCH PLAN

A three dimensional biomechanical analysis of five
subjects walking under two different conditions, shoe
alone and shoe plus orthotic. was performed. Experimental
data were simultaneously collected using high speed
cinematography and a force plate. For this study.
patients who had excessive pronation and had been
successfully treated by a podiatrist with a semirigid
orthotic served as subjects. All subjects wore the same
type of shoes (Brooks Tempo) for testing. This shoe was
chosen because it incorporated a design which would not
have any interactive effect on the test conditions. The
methods used in this study incorporated rigid body
mechanics and the Newton-Euler equations of motion. The
abduction-adduction moment at the knee joint was
calculated for each subject from the three dimensional
kinematic and kinetic data. The abduction—adduction
moment at the knee joint was given in Newton—meters and
displayed graphically as a function of stance phase. The
graphs were then compared for general patterns and trends
in the abduction-adduction moment.
IV. ASSUHPTIONS AND LIMITATIONS

It was assumed that during each trial the’ subjects
exerted a similar' effort and that the orthotic material
was consistent for all subjects. The lower extremity was
assumed to be a linkage of physically united rigid bodies

transmitting forces and moments. In this manner all

9
physical connections of one body segment with the other
allowed the equations of rigid body mechanics to be used
to determine the resultant forces and moments transmitted
across the joint surface which separates the two adjacent
body segments.

The limitations of the study were. first. the small
sample size which was obtained from a single podiatric
practitioner. and second, that the abduction-adduction
moment was calculated from kinematic and kinetic data. not
measured directly.

V. SIGNIFICANCE OF THE STUDY

The findings of this study made a valuable
contribution by filling a void in the present body of
knowledge on orthotics. This study provided an objective
analysis of the biomechanical effects that orthotic
appliances have on knee joint mechanics. A better
understanding of these biomechanical effects could lead to
better design of orthotic appliances and make the
prescribing and fitting of orthotic appliances more cost
and time efficient. relying less on trial and error.
horeover. this study also provided much needed information
on an objective technique in which to evaluate lower
extremity dysfunction in a dynamic. closed kinetic chain
condition. This study provided information which could be
useful to practitioners. Specifically. the information
may contribute to more consistent success in controlling

abnormal foot function. the elimination of resulting knee

10

symptoms and the prevention of the development of abnormal
knee motion.
VI. DEFINITIONS

Abduction. Movement of a body part away from the
midline of the body.

Adduction. Movement of a body part towards the
midline of the body.

EQEEEHS The measure of the tendency of an applied

force or forces to produce rotation about some fixed point

or axis.
Normal Walking. Normal is referred to as the
nonpathological or uninjured state. Hence. normal walking

is locomotion whereby one foot is always in contact with
the ground in the absence of signs and symptoms of injury.

Orthgtig. An orthotic is a straightening or balancing
device that is custom made from a neutral cast of the
foot. It can be made from semiflexible or rigid material
depending on the amount of control needed. An orthotic is
prescribed by a physician.

Stance phase of gait. Stance phase is that period
during the gait cycle occurring between heel contact and

toe off for a single limb.

REVIEW OF THE LITERATURE

Two main areas in the literature were identified as

relevant to the purpose of this study and were therefore

reviewed. First. an

biomechanics defined as gait analysis.

research on orthotic therapy.

overview

of the branch of

followed by current

will be dicussed.

I. GAIT ANALYSIS
Gait analysis is defined as a quantitative
description of human locomotion (Chao. 1985). Human

locomotion is the action by which one's body is propelled

through space. Locomotion

is

achieved by coordinated

movements of the body segments employing an interplay of

internal and external

analysis studies began as early as 1680 by Borelli.

form of simple observational methods.

cinematography in 1887.

studies not only by providing

permitted detailed. objective
phenomenon but. also by
'capture' these observations

quantitative aspects of gait
1895,
body segments

as rigid

11

forces

bodies

(Cappozzo. 1984). Gait
in the

The development of

facilitated the growth of gait

a systematic method which

observations of the gait
providing a means to
for later viewing. The

analysis studies began in

when Braune and Fisher began to represent the human

while introducing the

12

technique of stereophotogrammetry into the studies of
human gait (Cappozzo. 1984). In the early 1900’s
reproducible measurements of foot forces began using
pneumatic force transducers which measured the three
components of force from both the right and left feet.
During the same time. the point of force application or
center of pressure utilizing the centroid of vertical
forces. was first determined (Cavanagh. 1982). Since then
human walking has been extensively studied by many
investigators (Andriacchi. Olge. & Galante. 1977; Dec.
Saunder. Inman. & Eberhart, 1953: Murray. 1967; Simon.
Trieshmann. Burdett. Ewald. & Sledge, 1983).

Gait analysis studies can be divided into three
general areas: (A) kinematic study of segment and joint
motion. (8) foot/ground reaction forces and center of
pressure analysis and. (C) internal joint and muscle force
prediction. This study incorporated information from each
of these areas in the description of the effects of
orthotics on the mechanics of the knee joint during the
stance phase in walking gait. Appropriate consideration
was given to each area as it pertained to this study.

A. KINEMATIC STUDIES

The kinematic area of gait analysis consists of many
diversified studies which have attempted to quantify
normal and abnormal (pathological) gait characteristics.
For example. several investigators (Murray. Drought. &

Ross. 1964; Murray. 1967: Murray. Kory. & Sepic. 1970:

13

Saunders et al.. 1953) have thoroughly described the
temporal and distance patterns of normal gait. Other
kinematic studies have shown that many gait parameters
were velocity dependent and that a change in one of the
parameters, such as cadence, produced changes in the
overall gait pattern (Andriacchi et al.. 1977; Dillman.
1974; Smith. McDermid. & Shideman. 1960). These
descriptions of gait patterns and parameters served as the
fundamental base on which joint motion. ground reaction.
joint. and muscle forces could be evaluated.

Description of lower extremity joint motion in the
sagittal plane during gait has been studied extensively
(Dec et al.. 1953; Murray. 1967). However. normal walking
involves a complex three dimensional motion of a multiple
linkage system. The techniques which allowed for
description of this three dimensional motion of the human
body have been available since the end of the last
century. but the clinical application of the information
has been difficult. Therefore. many of the kinematic
studies performed on gait have been two dimensional in
nature in order to provide clinically understandable and
useful information. Within the last decade. investigators
(Andracchi. Anderson. Fermier. Stern. & Galante. 1980;
Andriacchi. Galante. & Fermier. 1982; Harrington. 1983
Simon et al.. 1983). have been successful at providing
clinically understandable three dimensional analyses of

joint motion in normal and pathological states.

14

In order to describe three dimensional joint motion
in the lower extremity during gait. localized coordinate
axes must be defined on the basis of underlying skeletal
structures and properly placed surface markers attached
directly on the skin. Once the spatial locations of these
markers and their relative relationship with the bone
orientation are known. the joint motion can be calculated
following the classical mechanical method (Chao. 1985). In
using this method it must be assumed that joint
translation is very small. Furthermore. all joint motion
recorded in kinematic studies of walking or running gait
should be classified as gross motion since the motion
does not reflect the true articulating joint surface
motion (Chao. 1985).
B. FOOT-GROUND REACTION FORCE AND PRESSURE

The second area in gait analysis is the study of foot-
ground reaction and center of pressure patterns. Many of
the studies in this area measure the relative forces
between the foot and the ground utilizing a piezo electric
or strain gage force plate capable of recording the
vertical. anterio-posterior. and medic-lateral components
throughout the stance phase of gait (Chao. 1985). The
resultant force point of application (center of pressure)
can be determined in reference to the force plate
coordinate system or to the foot—shoe itself. If the
positions of the lower extremity (kinematic data) are

known during the stance phase when this force information

15

is recorded. then the external moment due to the foot-
ground reaction force vector can be assessed at a joint.
Measurement of the ground reaction force using a force
plate does not give pressure distribution on the foot but
only location and magnitude of the resultant force of the
pressure system (Soutas-Little. Ulibarri. Goodman. & Hull.
1987)- In order to measure pressure distribution beneath
the foot. discrete transducer elements are either mounted
in a walkway or applied directly to the plantar aspect of
the foot (Cavanagh & As. 1980). This type of device
provides information concerning the area of contact and
the intensity of contact pressure in localized regions of
the foot.

Evaluating gait using the ground reaction forces has
significant clinical value. since it is thought that many
lower extremity and low back problems are associated
either directly or indirectly with foot structure or foot
function during the support phase of gait (James. Bates. &
Osternig, 1978). Many investigators. (Cavanagh & As.
1980; Cavanagh & LaFortune. 1980; Grundy. Tosh. McLeish. &
Smidt. 1975: Stokes. Stott. & Hetton. 1974) have
attempted to describe normal foot-ground reaction forces
and center of pressure patterns in walking and running.
Other studies. (Beekman. Louis. Rosich. & Coppola. 1985:
Jacobs. Skorecki. & Charnley. 1972: Katoh. Chao. Laughman.
Schnieder. & Murray. 1983) have compared the foot-ground

reaction forces and center of pressure patterns in normal

16

and pathological gait patterns. finding distinct patterns
of similarity in normal gait and significant abnormalities
in the pathological states. Bates. et a1. (1983)
investigated the interactive nature between subjects and
different types of shoes with respect to ground reaction
forces :u: an attempt to evaluate the effects of several
types of shoes on the ground reaction force in runners.
They concluded that there was no best shoe for all runners
due to the unique anatomical structure and biomechanical
characteristics of individuals. Therefore. the attempt to
find an optimal running shoe design appear to be
unimportant. More important in a running shoe design
would be a shoe which contributed to the effectiveness of
an orthotic device.

The evaluation of orthotics through using of center
of pressure calculations is limited by the difficulty of
establishing normal patterns of the center of pressure for
a general population. There is an inherent variability
in the center of pressure distribution and ground reaction
forces for individuals which complicates the establishment
of normal patterns (Cavanagh & LaFortune. 1980). Cavanagh
and LaFortune (1980) have suggested that more powerful
techniques for the identification of pathology would be a
comparison of the results from the same individual in an
injured and uninjured state. For an individual needing a
prescribed orthotic, the injured state would be gait

without the orthotics in the shoes and the uninjured state

 

17

would be gait with the' orthotic in the same shoes. The
resultant shoe-ground reaction forces may be different
between these two conditions. i.e. the injured and
uninjured states. Acrun and Brull (1976) reported. that
the quantitative effects of orthopaedic appliances and
devices may be evaluated from dynamic foot-ground forces.
C. JOINT AND MUSCLE FORCE ANALYSIS

The final area of gait analysis to be discussed deals
with the forces that caused the observed motion. This area
is called kinetic analysis of gait. There are two groups
of forces acting on the body: internal and external. The
internal forces are those transmitted by body tissues and
consist mainly of muscular forces. tension forces in
ligaments. and joint contact forces. The external forces
consist of those which result from the physical
interaction between the environment and the body.
Examples of these external forces are the gravitational
and ground reaction forces. The external forces can be
easily measured or reliably calculated. relative to the
measurement of internal forces which often requires
invasive techniques. In order to avoid invasive
techniques. the internal forces must be predicted based on
motion data. ground reaction force data and inertial
properties. In reference to kinetic analysis. Chao (1985)
concluded: "the incomplete and imprecise kinematic data of
limb movement during gait and the extremely complex

anatomical geometry and inertial properties of the

18
musculoskeletal systems make the force analysis in gait
one of the most challenging tasks in biomechanics' (p.
237).

The force analysis problem is often solved using many
assumptions and over simplifications in modeling and may
involve complicated computations. Practical. clinically
useful information is difficult to obtain. However, it has
been concluded by Andriacchi. et a1. (1980). that useful
information in terms of joint moments appear to be
valuable in assessing functional effects of therapeutic
and rehabilitation procedures. In a second study,
Andriacchi et al. (1982), used the moments of the knee
joint to evaluate total knee replacement design. The
moments at the knee joint were due to the resultant ground
reaction force. Therefore, slight changes in the
resultant ground reaction force may be significant in the
pathological knee abduction-adduction moment. Since knee
pain may result from a pathological abduction-adduction
moment. comparisons of the knee abduction-adduction moment
in an injured and uninjured state would be of major
clinical relevance.

II. ORTHOTIC THERAPY

The intent of orthotic therapy is to support the foot
in its neutral position in order to prevent excessive
forces and motion while allowing normal joint function and
pain free activity. The orthotic device itself is a

straightening or balancing device with its main objective

19

to maintain the foot in its neutral position throughout
the walking and running gait cycle. In accomplishing this
objective, an orthotic prevents excessive. inefficient.
compensatory motion and the abnormal forces associated
with compensation (Eggold. 1981). The major purpose when
treating patients with orthotics is to restore 'normal'
biomechanical function of the lower extremity, i.e.
asymptomatic biomechanical function. The ability to
quantify any biomechanical changes in the function of the
lower extremity as a result of the use of orthotics is
of major clinical importance. The ability to establish
objective biomechanical information depends on utilization
of efficient measurement techniques and data analysis
methods. Joint motion of the lower extremity and ground
reaction force parameters during the stance phase of gait
are important in the biomechanical assessment of the
effects of orthotics on the lower extremity during gait.
since the ground reaction forces represent the total
effect of functional and mechanical alterations in the
lower extremity linkage (Knutzen & Bates. 1988). These
parameters can be identified and analyzed through the
techniques and methods of gait analyses previously
discussed.

James. Bates. and Osternig (1977). suggested that
many of the lower extremity problems encountered by
runners were either directly or indirectly related to foot

function during the support phase of gait. It could also

20

be argued that this concept applies to nonrunners who are
experiencing chronic. nontraumatic lower extremity
problems. such as chondromalacia patella. It has been
reported (Eggold. 1981; James. 1975; Newall & Bramwell.
1981) that many of these lower extremity problems could be
alleviated by the use of an orthotic appliance. However.
few studies have quantitatively investigated the use of
orthotics. host of the studies on the effectiveness of
orthotics have either been based on results of surveys of
runners who have been treated with orthotics (Eggold.
1981). or descriptive case studies (Newell & Bramwell.
1984). D'Ambrosia and Douglas (1982). stated 'orthotic
treatment. in the form of foot supports. will relieve the
eylptoms. and combat the causes of chondromalacia
patella. and at the same time allow the distance runner to
get back on the road again" (p. 161). In addition.
Subotnick (1975) reported that rigid orthotics were very
successful in relieving symptoms of chondromalacia.

The most common abnormal foot structure is the
pronated or flat foot. A variety of orthotic devices have
been developed to manage the pronated foot. Clinically.
orthotics are prescribed to alter foot and leg motion.
through redirection of the ground reaction forces. and to
aid in shock absorption (Smith. Clarke. Hamill. &
Santopietro. 1986). There are three categories of
orthotics: rigid. semirigid. and soft.

Rigid orthotics are made from a non-weight bearing

21
neutral cast of the foot or they also may be molded
directly on the patient’s foot. Rigid'orthotics are made
of rigid plastic material which reduce the shock
attenuation ability and energy absorbing movements of the
foot (Lockard. 1988). For this reason. rigid orthotics
are often utilized to accommodate foot structural
deformities and they are best suited for walking and edge
control sports such as skiing. Rigid orthotics are not
usually well tolerated by runners. Semirigid orthotics
are made from a non—weight bearing neutral cast of the
foot. The semirigid orthotics are used to provide some
softness and reduce impact forces. However. semi-rigid
orthotics are more commonly used to balance the malaligned
foot in a neutral position to reduce abnormal foot or leg
movements (Lockard. 1988). These orthotics use rubber
posts at the rear-foot and fore-foot to control the motion
and provide some cushioning. A semirigid orthotic is
often used in sport applications where correction is
required under high-impact loading; e.g. basketball.
track. baseball. etc.. Soft orthotics are composed of
felt and other soft material that will adapt to the shape
of the foot in order to provide cushioning to improve
shock absorption. to reduce plantar surface shearing or to
control abnormal motion of the foot in cases of mild
biomechanical imbalances (Lockard. 1988). Soft inserts
do not require custom molding and are available

commercially. These are often temporary devices. used to

22
determine whether permanent orthotics are needed
(Subotnick. 1983).

The most frequent method of quantifying the effects
of orthotics has been kinematic analysis of rearfoot
motion. This rearfoot motion consists of eversion or
inversion of the calcaneous relative to the lower leg and
is thought to be an accurate predictor of how much
pronation is occurring during the support phaBE' of gait
(Smith. et al. 1986). However. there exist many problems
with this rearfoot method of analysis which may lead to
inaccurate conclusions. Some of these problems are: the
assumption that pronation can be accurately predicted by
calcaneus eversion when pronation is a triplanar movement;
attempting to measure motion occurring at the subtalar
joint by external. surface markers; that the rear foot
motion being described is actually rear shoe motion; and
in two dimensional sagittal plane analysis one encounters
distortion of the projected angle between the calcaneous
and the lower leg (Soutas-Little. et al.. 1987).

Hamill and others (1986). used an in shoev pressure
sensor system to evaluate the interaction between orthotic
appliances and running shoes and concluded that the
addition of a semirigid orthotic appeared to control the
foot at impact better in a rigid midsole shoe than in a
soft midsole shoe. In a study by Burdett. Kohrt. and
Buchbinder (1985). the effects of orthotics on frontal

plane knee kinematics were investigated. They stated that

23
since past studies have indicated orthotics were
beneficial in controlling excessive pronation at the
subtalar joint. it may be likely that an orthotic device
would also control a similar motion at the knee. i.e.
excessive abduction-adduction. However. the results from
their study were inconclusive.

Orthotics are frequently prescribed in the management of
lower extremity problems. Considering the paucity of
kinetic investigations on the effects of orthotics. it
appear that the mechanics of orthotic devices are poorly
understood. This lack of kinetic information may be a
contributing factor to inappropriate and excessive

prescription of orthotic devices.

METHODS

The purpose of this study was to determine the
effects of an orthotic appliance on the abduction-
adduction moment occurring at the knee joint during the
stance phase of walking gait. Five male volunteers served
as subjects for this study. Four of the volunteers were
obtained from a podiatrist’s patient population based on
the following requirements: all subjects were diagnosed as
excessive foot pronators with past complaints including
knee pain. the subjects were currently using prescribed.
semirigid orthotics during walking or running activities.

and the subjects had no history of previous. unrelated

lower extremity injuries (i.e.. fractures. sprains or
surgeries). The fifth volunteer was an asymptomatic
runner and a graduate student. All subjects were fully

informed about the study and signed a written consent form
to participate in the study. Each subject’s right leg was
targeted for filming according to the research protocol
(See Appendix). Anthropometric measurements were taken
prior to the trials. These measurements consisted of
total body weight. and width and length of the right
tibia. All of the subjects wore a similar shoe (Brooks

Tempo) during the trials. Each subject was required to

24

25

complete two satisfactory trials under two conditions.
Satisfactory trials were determined by this investigator
based on whether the complete foot contacted the force
plate while the cameras were properly timed in capturing
the movement. The first condition consisted of walking
without the orthotic in the shoes and the second condition
consisted of walking with the orthotic in the shoes.
These conditions produced the pathological and non-
pathological states for each of the subjects.
respectively. The order of these two conditions was
consistent for all subjects. All of the subjects received
similar instructions prior to the trials and as many
practice trials as necessary were allowed.
I. DATA COLLECTION PROCEDURES

The shank and foot were considered to be a rigid
body. The targeting scheme is shown in the Appendix.
Four targets were placed on the surface of the shank over
the following bony landmarks: [d] lateral malleoli. [e]
distal tibia just proximal to the tibialis anterior
tendon. [f] tibial tuberosity. and [g] lateral tibial
condyle. This targeting scheme was established to
facilitate recording of kinematic parameters (linear
positions. velocities. and accelerations) of the shank and
also to locate the center of mass of the shank segment and
the center of pressure relative to the shank. The
placement of the targets allowed for the solution of the

inverse dynamics problem encountered in analyzing the

26
motions of a rigid body when the forces and moments
required to create those motions are unknown. The
objective of this procedure was to determine the unknown
forces and moments acting at the knee joint.

Two 16 mm LOCAH high speed cine cameras were used to
film the subjects as they walked across a force plate and
recorded the kinematic activity* of the right lower leg.
The» cameras were placed at angles to the plane of gait
allowing both cameras lateral-anterior views of the right
lower extremity. The cameras were started and stopped
simultaneously. Film speed was set at 100 frames per
second and the shutter angle was set at 120 degrees
allowing for a 1/300 of a second exposure. Prior to
filming the trials. a calibration structure was placed on
the force plate and filmed in order to provide' control
points for the direct linear transformation (DLT)
technique used (Walton. 1981). Synchronized timing lights
accurate to 1/1000 of a second were placed in the field of
view of both camaras so that both sets of kinematic data
could be time—matched. An AHTI Force-Torque (Hodel ORG)
dynomometer was used in conjunction with an IBM 9000
dedicated computer for simultaneous collection of three
dimensional force and moment data at a frequency of
1000Hz. The kinetic data were stored on a floppy disk.
then transferred for analysis to the Prime computer in the
Computer Aided Design Laboratory in the College of

Engineering at Hichigan State University. The digitized

27
kinematic data were also transferred to the Prime Computer
for analysis. '
II. ANALYTICAL HETHODS

Data analysis consisted of the evaluation of a single
right stance phase for all subjects over two trials for
the two described conditions. The three dimensional
kinetic and kinematic experimental data were then post-
processed.

Film data from both cameras were quantified using an
ALTER Datatab rear projection system. Every other frame
of data was digitized and began 10 frames prior to right
heel strike and ended 10 frames after right toeoff. The
order of digitization of the targets on the right lower
extremity was done according to the study protocol (See
Appendix). The coordinate data for the two views was time
matched by linear interpolation and then three dimensional
coordinates of the right lower extremity targets were
computed using the DLT technique. The fixed laboratory
coordinate axes were defined by the calibration structure
filmed during the experimental protocol which defined the
z-axis as perpendicular to the ground. positive in the
superior direction. The x-axis was formed perpendicular
‘u: z and positive in the direction of motion. and the y-
axis was derived perpendicular the z and x axes and was
positive in the medial direction with respect to the right
leg.

The force plate measured the resultant force vector

28

and the moment vector acting on the platform by the foot
during the stance phase of gait. The direction of the
forces and moments recorded by the force plate were
reversed to obtain the forces and moments acting on the
foot by the ground. The resultant force and moment
vectors. 3 and i. were recorded with respect to the origin
and axes of the force plate coordinate system. as shown in
Figure 1. The moment vector was resolved through vector
analysis into two vectors: one perpendicular to the
resultant force vector and the other parallel to the
resultant force vector. The intercept of the resultant
force vector and the parallel moment vector with the
surface of the force plate defined the center of pressure
(Soutas-Little. et al.. 1988). The center of pressure was
computed with respect to the force plate coordinate
'Ystem. The resultant force vector. the parallel moment
vector. and the center of pressure were then transformed
by a series of matrix equations to the lab coordinate
system and then to the local or body coordinate system.

The abduction-adduction moment acting at the right
knee was computed in terms of a local coordinate system
aligned with the principal axes of the shank. The origin
of this local coordinate system was chosen to be located
at the segmental center of mass of the shank defined by
Dempster (1955). The center of mass of the shank was
located from the kinematic and anthropometric data
obtained in this study. The schematic representation of

the shank segment is shown in Figure 2. including the

29

301
3)

 

.9‘

Figure 1. The Force Plate Coordinate Axis and the

Ground Reactions.

30

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 2.

Schematic Representation of the Shank

31

local coordinate system located at the center of mass of

the shank. and the components of the external forces and

moments acting on the segment: with reference to the

direction of motion. position of the cameras and the lab

coordinate system. The Newton-Euler equations of motion
for the shank which were used to calculate the moments and

forces acting at the knee joint were as follows:

R31 - m‘.cm1 - 91) - R1 [1]
R32 - m(acmz - 92) 2 [2]
R33 - m(acma - gs) 3 [3]
n I ° I n
31 1'1 ' '2'3‘12 ' 3’ 1
- (rcpcmZR3 - rcpcm3R2) - rpcm2Rj3 + rpcmBRJZ [4]
0
H32 8 12w2 - w:3wl(I:3 - 11) H2
- (rcpcm3R1 - rcpcm1R3) rpcmale + rpcmle3 [5]
!
H33 13'3 - w1w2(I1 - 12) ha
- (rcpcm1R2 - rcpcm2R1) rpcmleZ * rpcm2Rj1 [6]

where:

a 1 were the principle components of the acceleration of

CIII

the center of mass of the shank.

I were the principle components of the inertia tensor.

1

:1 were the

acceleration.

principle

components

the

angular

32

and w1 were the principle components of the angular
velocity.

A numerical method. based on the method of least
squares as described by Verstraete and Soutas-Little
(1990). was used to determine the angular acceleration and
angular velocity of the shank from the three-dimensional
kinematic data. The Newton-Euler equations were expressed
with respect to the principal axes and center of mass of
the shank. where 1. 2. and 3 refer to the principal

directions of the coordinate system. A positive force and

moment convention was assumed. The vector rcpcm

represented the relative position vector between the
center of pressure and the center of mass of the shank.

The vector. 1? represented the relative position

pcm'
between the center of mass and the knee joint center.
H31. in equation (4). was the abduction-adduction moment.

The inertial effects during walking of the foot on the

knee abduction-adduction moment were considered
insignificant (Verstraete. 1988) and ‘were ‘therefore
excluded in this analysis. The knee joint was assumed to

consist solely of the proximal portion of the tibia and
the distal end of the femur. The center of the knee joint
was defined to lie on the contact surface of the tibial
plateau. at a point midway between the lateral and medial
tibial condyles (knee width). In this analysis the knee
joint center was used as a :reference ‘point of contact

between the shank and thigh segments. The forces and

33
moments in the tibia were resolved with respect to this
central linkage point defined on the proximal surface of
the tibia. The computed moments acting at this linkage
point. the defined center of the knee joint. were computed
in Newton-meters and graphed as a function of percent of

stance phase. The graphs were then compared for general

patterns and trends in the abduction-adduction moment.

RESULTS AND DISCUSSION

The results of the analysis of the three-dimensional
kinematic and kinetic data consisted of the computed
abduction-adduction moment acting at the defined center of
the knee joint. These results were obtained from test on
the right lower leg' of four male subjects during the
stance phase of walking gait with and without the
application of an orthotic appliance. Subject 5 was not
included in these results due to a technical error in data
collection. Since Subject 3 was an asymptomatic runner.
he was not tested walking with an orthotic and thus served
as a control. The results were expressed in Newton-meters
and presented graphically as a function of percent of
stance phase. The action of this moment corresponded to
the rotational motion of the distal shank segment
relative to the thigh segment. According to the positive
convention assumed in this study. a positive value for
the computed moment would indicate abduction. while a
negative value would indicate adduction. Therefore. an
adduction moment would tend to cause a varus angulation at
the knee and an abduction moment would cause a valgus
angulation. The graphs were analyzed for general patterns

and trends across all trials for both conditions for

34

35

each subject. The results will be presented in two
parts. first for the condition without the orthotic
appliance and second for the condition with the orthotic
appliance. The discussion of these results follows and
includes comparisons between the two conditions.
I. CONDITION I: WALKING WITHOUT ORTHOTIC

The abduction-adduction moment acting at the linkage
center of the knee joint for both trials for each subject
walking without an orthotic appliance in the shoe is
displayed in each graph in Figure 3. In all subjects. the
abduction-adduction moment displayed a predominant
adduction action during the stance phase. The pattern of
the abduction-adduction moment among the subjects was a
consistent trend which could be depicted as a 'W' shaped
curve. Each curve was found to have three peaks or points
of change in direction. The mean values of the peaks of
the abduction-adduction moment curves for both trials for

each subject are given in ‘Table 1. For each subject.

TABLE 1. Mean Values of the Abduction-Adduction
homent Without Orthoticfi

PEAK l PEAK 2 E§A§_§_
SUB l -100 -55 -80
SUB 2 -90 -4O -75
SUB 3 -65 -4O -55
SUB 4 -llO -80 -100

*expregsgd in Newton-meters

 

 

 

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Abduction-Adduction Homent acting at the Knee
Walking Without an Orthotic.

37

peak 1 was the largest and peak: 2 was the smallest.
Comparison of the mean values amoung subjects showed that
Subject 3. the control. had overall lower values than the
other. pathological. subjects. The numbers in Table 1.
as well as the graphs in Figure 3. showed that the
abduction-adduction moment tended to progress in a
predictable manner during the stance phase. Analysis of
the graphs. specifically the magnitude of the adduction
moment. revealed the following pattern: there was a
increase in the adduction moment during the first 30% of
the stance phase. then an inconsistent decrease to 50-60%
of the stance phase and then again an increase. until 90%
of the stance phase. At 90% of stance phase the adduction
moment showed a consistent decrease to toe off. The
graphs were found to be highly reproducible within subject
trials. There was slight variation in the graphs between
the trials for each subject which could be attributed to a
variation in walking speed between trials. The only
noticeable variation in the 'W' pattern was the amount of
fluctuation between the peaks of the abduction-adduction
moment among the subjects. The general pattern of the
abduction-adduction moment displayed by these results were
consistent with those described by Andriacchi and
Strickland (1985) and Verstraete (1988).
II. CONDITION II: WALKING WITH ORTHOTIC

The resultant abduction-adduction moment computed at

the knee joint for the condition of walking with an

38
orthotic appliance for each subject over both trials are
displayed in Figure 4. Subject 3. the control. was not
tested walking with an orthotic. The actions of the
abduction-adduction moment corresponded to the same
rotational motions of the shank segment relative to the
thigh segment as presented earlier in this chapter.
Again. the abduction-adduction moment was analyzed for
general patterns and trends in the magnitudes. Over all
trials. the abduction-adduction moment displayed a
predominant adduction moment. Similarly. the progression
of the abduction-adduction moment computed for these
trials exhibited a predictable trend. The adduction
moment increased during the first 25% of stance phase.
which was followed by a decrease in the adduction moment
until 55% of stance phase. Next the adduction moment
increased until 90% of stance phase. and then the
adduction moment steadily decreased to toe-off. This
general pattern was very similar to the pattern displayed
for the abduction-adduction moment in the trials without
the orthotic. The pattern of the abduction-adduction
moment was also a 'W" shaped curve. The only noticeable
variation in this 'W' pattern was the amount of
fluctuation between the peak values of the abduction-
adduction moment among the subjects. with the most
noticeable differences occurring between Subject 1 and

Subjects 2 and 4. The mean values of the peaks of the

39

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 4. Abduction-Adduction Homent acting at the Knee
Walking With an Orthotic.

4O
abduction-adduction moment curves for both trials for each
subject are presented in Table 2. Here again. the mean
values of peak 1 were the largest and the mean values of
peak 2 were the smallest. The peak values for Subject 1
showed an overall considerable decrease when compared to
the numbers in Table 1. This could reflect the effects
of a properly fitted orthotics. The mean values for
Subjects 2 and 4 were essentially unchanged from Table 1.
This could reflect unnecessary or improperly fitted

orthotics which had no effect on the abduction-adduction

moment.

TABLE 2. Hean Values of Abduction-Adduction Homent
With Orthotic.

2225.1. Esak_2 £225.;
sun 1 -45 ~20 -4o
sun 2 -90 -40 -7o
SUB 4 -110 -70 -1oo

*gggressed in Newtog-meters

III. DISCUSSION AND COHPARATIVE ANALYSIS

It is important to realize that variations between
the two conditions discussed here may be due to
natural responses of the subjects. environmental
effects of the testing conditions. and/or experimental
errors. Furthermore. another factor limiting the accuracy
of the calculation of the abduction-adduction moment

occurring at the knee was the definition of the actual

41

knee joint center and the location of the center of mass
of the shank from external markers. Nevertheless. the
approach taken in this study was similar to those taken in
other related studies that have been described in the
literature. Noreover. since a consistent definition of
the center of the knee joint and center of the mass of the
shank were used. the results are comparable.

The graphs in Figure 5 show the differences in the
abduction-adduction moment between the trials without the
orthotic (N3 and N4) and the trials with the orthotic (W2
and W3) for Subject 1. The most obvious difference was
that the adduction moment was much less in the trials with
the orthotic. Also. the shape of the 'W" curve is much
less evident in the trials with the orthotic. There was
less fluctuation in the adduction moment in trials with
the orthotic.

The differences in the abduction-adduction moment
between the trials without the orthotic (N3 and N5) and
the trials with the orthotic (W2 and W4) for Subject 2 are
shown in the graphs in Figure 6. There was much less
differences between the two conditions for this subject.
However. when the mean value of the moment over the two
trials for each condition was compared to each other.
there was a subtle. yet. consistent difference whereby the
adduction moment was slightly less in the trials with the
orthotic. The shape or the fluctuation of the 'W' curve

was not noticeably different between the two conditions

42

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 5. Subject 1 Abduction-Adduction Homent Across

Conditions.

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l
1 1 1 1
‘5.
\
\
/

 

 

 

 

 

 

 

 

'1.
q
d
.4
’1” T T ‘ I I
0 as 0 6‘ 9° “’9
SYNC: m
“EH.&

Figure 6. Subject 2 Abduction-Adduction Homent Across

Conditions.

44

for this subject.

The graphs in Figure 7 show the differences in the
abduction-adduction moment between the trials without the
orthotic (N2 and NS) and the trials with the orthotic (W1
and W3) for Subject 4. The difference between the two
conditions for this subject was not noticeable. The 'W'
pattern of the curve of the abduction-adduction moment was
more evident in the trials with the orthotic. There was
slightly more fluctuation in the second peak of the
adduction moment in the trials with the orthotic. but this
difference was minmal.

The numbers in Table 3 show the differences in the
mean value of the peak magnitudes of the abduction-
adduction moment across the two conditions for each

subject. A positive difference corresponded to a decrease

TABLE 3. Differences in Mean Peak Values of the
Abduction-Adduction Moment across Conditions

PEAK l PEAK 2 PEAK 3
SUB 1 +60 +35 +45
SUB 2 0 +5 *5
SUB 4 O *15 O

gxgrggged in Newton-meters

1n the adduction moment magnitude. All of the measurable
differences between the two conditions were positive

values. indicating that the adduction moment influence was

less in the trials with the orthotic.

45

 

 

'2 ....... “I -————"
05'
4
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H q
T
o '3 .r**
n d
I H
q

 

mun-an)
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.\
. \
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I
I
I
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3
C
O
f
'.
I
I
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d” V.” /
< hi
1
4
.4
'19 1 T 1 1 1
0 20 ‘0 6. N I"
'4 STNCI m
WJ)‘
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a
n 1
E «4
H J
g . = r
n ‘ . ’f
1 "1..
4 .
.. . 5
E Q, I
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9 d / _...
s < // ~\ I.
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4“ - (. ' ‘~..
4 ‘—s
.4
d
d
‘19 1 1 I I I
C a! ‘0 6. a. I”

Figure 7. Subject 4 Abduction-Adduction Homent Across

Conditions.

46

An adduction moment at the knee joint would be
balanced by tension in the lateral ligaments and a
reactive joint contact force medially (Harrington. 1983).
The clinical significance of a decrease in the adduction
moment would be the decrease in the compression forces in
the medial compartment of the knee joint. This could
account for the decrease in knee pain which has been
reported with orthotic therapy. But that remains unknown
at this time. The comparison between the two conditions
for Subject 1 showed a noticeable decrease in the
adduction moment walking with the orthotic. This could
imply a properly prescribed and fitted orthotic.
Whereas. the comparisons between the two conditions for
Subjects 2 and 4 showed very minimal to no noticeable
differences and this could imply inappropriately

prescribed or improperly fitted orthotics.

CONCLUSIONS

The prescribing of foot orthoses has been effective
in reducing the lower extremity problems. including knee
pain. in recreational athletes (Donatelli. et al.. 1988).
The application of an orthosis has been an effective
external support mechanism that altered the lower
extremity function by influencing the medic-lateral
function of the foot (Bates. 1979). It has been well
established by previous research that the mechanical
behavior and forces occurring at the foot plays an
integral role in the function of the entire lower
extremity during the stance phase of gait (Bates. et al..
1982: Ratch. et al.. 1982: McPoil & Knecht. 1985: Morris.
1976). Furthermore. the relationship between foot function
and knee joint pathology has been well substantiated
(Buchbinder. et al.. 1979: Davies & Malone. 1980: Eggold.
1981; Lutter. 1980). Kinetic variables have been used
primarily to identify’ gait abnormalities. evaluate shoe
performance, and in describing general mechanical concepts
of individual joints of the lower extremity (Bates. et
al. . 1979: Morrison. 1970; Simon. et al. . 1983) .
Recently. attempts been made to examine kinetic

alterations with respect to knee joint kinematic

47

48

parameters (Knutzen a. Bates. 1988). Yet to date. there
have been no studies which have specifically attempted to
relate knee resultant forces and function with ground
reaction forces. Basic mechanical principles require that
the external moments acting on a joint. such as the knee
joint. be counteracted. by equal and: opposite internal
moments. In most cases. the external moments would most
likely be balanced by' a combination of muscle forces.
ligamentous tension and joint contact forces. However. if
these forces were unable to restrain the external moments.
there would then exist abnormal compensatory motions.
Another mechanism by which abnormal compensatory motions
could develop would be the result of prolonged. repetitive
misdirected external forces acting on a joint causing
weakening of the internal restraining structures.
Consequently. it is plausible that determination and
possibly even prediction of knee joint pathology should be
evident in analysis of moments occurring at the knee
joint. when computed from three-dimensional kinetic and
kinematic data collected on the lower extremity' during
gait.

Quantitative research on the effect(s) of orthotic
devices on the resultant forces in the lower extremity is
severely lacking. Therefore. the mechanical effect of
orthotic therapy on the lower extremity is not known.
Determining the kinetic parameters which contribute to

knee joint pathology is important for clinicians who are

49
concerned with controlling foot function to reduce knee
joint injuries (Knutzen & Bates. 1988). Subtalar joint
Pronation is characterized by medial-lateral kinematic and
kinetic parameters occurring in the frontal plane. The
correlating motions to subtalar joint pronation in the
knee joint are abduction-adduction. Considering that
mechanically. the stance phase forces represent any
functional alterations in the total lower extremity
linkage. then a relationship between the kinetic
parameters and the resulting function of the joints of the
lower extremity would seem logical. Therefore. the effect
01 the resultant ground reaction force and moment that is
transmitted to the knee joint is of considerable interest
for clinicians who seek a more objective assessment of
gait deviations and subsequent treatment interventions.
including foot orthoses. If kinetic parameters (can. be
used to predict knee joint mechanics. the clinical
importance would be significant for therapists.
PhYBicians. and podiatrists who seek a more objective
assessment of knee joint pathology and evaluation of
orthotic therapy. Analysis of the general patterns and
trends in the abduction-adduction moment acting' at ‘the
knee joint during the stance phase of walking gait with
and without an orthotic appliance was performed to
determine if there were any noticeable differences between

the two conditions.

The concepts of rigid body mechanics and the

50
Newton-Euler equations of motion were utilized to perform
a three-dimensional gait analysis. This analysis examined
the effects of foot orthoses on the computed abduction-
adduction moment acting at the defined knee joint center
for the right lower extremity during the stance phase of
walking gait. The abduction-adduction moment acting at
the knee joint was computed from kinematic and kinetic
data collected on four male subjects walking under two
conditions. shoe alone and shoe plus orthotic. A fifth
male subject who was a asymptomatic runner served as the
control and was only analyzed walking without orthotics.
The abduction-adduction moment was examined for
differences in general pattern and trends between two
conditions. The general pattern of the abduction-
adduction moment between the two test conditions among all
subjects was found to be a consistent 'W' shape and to be
predominantly a negative value throughout the stance phase
of gait. According to the convention used in the methods.
a negative value corresponded to an adduction moment.
There was noticeable variation of the fluctuation of the
'W' shape for all subjects but. there was no trend in this
variation. Comparison of abduction-adduction moment
between the two test conditions revealed that the
adduction moment was noticeably decreased in the condition
with the orthotic for Subject 1. This would suggest a
decrease in the medial joint compression forces at the

knee. which may result in decrease knee pain. Subject 1

 

51

may have a properly fitted orthotic. Comparison of the
abduction-adduction moment between the two test conditions
for Subjects 2 and 4 showed very minimal decrease to no
noticeable differences in the adduction moment. This may
reflect improperly fitted orthotics which have no effect
an the mechanics of the lower leg. In addition to these
findings. the methods used in this study allowed an
objective analysis of the forces and moments acting at the
knee joint and may provide physicians. podiatrists and
physical therapists with a method for objective assessment
of orthotic therapy.

Further studies in this area would be recommended.
Tiberio ( 1987) presented a theoretical model which
described compensatory internal rotation of the femur as a
result of excessive pronation leading to pathomechanics of
the knee joint. The moment of interest in this situation
would occur about the inferior-superior axis of the shank.
with its potential action occurring in the transverse
plane. Consequently. future studies should include the
moments acting about the inferior-superior axis of the
shank. as well as utilizing a larger sample size.
controlling the speed of walking. and obtaining the
medical history including specific information on

effectiveness of each subject's orthotics.

APPENDIX

APPENDIX

SUBJECT PREPARATION PROCEDURES

CONSENT FORKS
Consent forms were obtained from each subject.

TARGETTING SCHEhE

The right lower leg of all subjects were targetted with 4
cloth pom-pom targets as follows: [a] at lateral
malleoli. [b] at distal tibia. (c) at tibia tuberosity.

[d] at tibial condyle. These targets were also digitized
in this order (a to d).

 

ANTHROPOHETRIC hEASUREHENTS
Each subject had the following anthropometric measurements
recorded prior to completing their trials:
body weight
distance between targets at distal and proximal tibia
width at malleoli and tibial condyles.

SUBJECT INSTRUCTIONS

Subjects received instructions to walk at a normal-
comfortable pace across the walkway without looking down.
The subjects completed three 'good' trials without their
orthotics in their shoes first. and then completed three
'good' trials with their orthotics in their shoes. The

shoes to be worn during the trials were Brook's Tempo
running shoes.

52

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