Clinical Assessment of Human Gait
Deanna J. Fish, CPO
Jean-Paul Nielsen, CP
ABSTRACT
The mechanics of human gait involve
synchronization of the skeletal, neurological and muscular systems of the human body. This article will enhance the
gait assessment abilities and processes
of the novice clinician by providing a
brief overview of normal gait followed
by identification of pathological and
pathomechanical gait patterns. Also
presented is a systematic approach to
clinical gait assessment that emphasizes
the need for the development of clinically cost- and time-effective tools to document and quantify data in the assessment of human gait.
Introduction
The complexity of the interactions of
the various components of human gait
has been researched and documented
for many years. Modern technological
advances such as force platforms, electromyographic data, high-speed film
and computerized gait analysis laboratories have allowed new insights into
human bipedal ambulation. While
these advances have proven to be invaluable in explaining "normal" gait,
and to some extent "abnormal" gait,
the experienced clinician continues to
perform functional gait assessment in
the absence of most technological assistance.
As a result, one has to rely on a
trained clinical eye to capture all
phases of the gait cycle in a short period of time for functional analysis. This
requires a thorough understanding of
normal gait and a systematic approach
to the evaluation of abnormal ambulatory patterns.
Normal Gait Patterns
The term "gait" is used to describe a
particular manner or style of walking,
and the term "normal gait" is used to
present those parameters that have
been generalized across sex, age, genetic predisposition and anthropometric variables.
The eight subphases of "normal"
gait have been well-described by Perry
and include: initial contact (IC), loading response (LR), midstance (MSt),
terminal stance (TSt), preswing (PS),
initial swing (ISw), midswing (MSw)
and terminal swing (TSw)(1,2). However, without technological assistance,
these eight subphases of gait cannot be
reliably distinguished. Four divisions
for functional gait assessment procedures are necessary to accumulate relevant information in the analysis of normal gait. These include:
- Weight Acceptance (initial contact
and loading response)
- Stance (midstance and terminal
stance)
- Forward Progression (terminal
stance and preswing)
- Swing (initial swing, midswing and
terminal swing)
A gait cycle is defined as the time
between two successive occurrences,
for example, from a right weight accep
tance period to the next right weight
acceptance period (3). It has been wellestablished that dynamic ambulation
involves a stance phase of 60 percent of
the entire cycle and a swing phase of 40
percent (see Figure 1
). Two additional
periods of double-limb support exist
when both the right and left lower extremities contact the ground in opposite synchronization.
Seventy percent of the total body mass
is located in the head-arms-trunk (HAT)
segment (2). This mass progresses in a
hypothetical line of progression (LOP)
and is balanced during ambulation on
the lower extremities, which form the
remaining 30 percent of total body mass
(4). The body's ability to effectively balance this mass in both static and dynamic
situations is essential to the functional
goals of bipedal ambulation.
These goals include providing a stable base of support in stance, allowing
forward progression of the body mass
over the distal limb segments, maintaining minimum energy expenditure,
and employing appropriate mechanisms for shock absorption and dissipation of forces.
Figure 2
is a summary of the major
sagittal plane joint motions and functions during a complete gait cycle. All
joint angulations are approximations
based upon a consensus of current literature, and the reader should refer to
these reference sources for detailed
analysis of normal gait patterns. It
should be understood that the timing of
muscle actions to produce specific joint
motions is critical for a stable, efficient
bipedal mode of ambulation. Even minor disturbances of the neurological
control mechanisms, motor input and
structural skeletal alignment can have
a significant effect on dynamic stability
and on functional and energy-efficient
gait.
Pathological Gait
Pathological gait describes altered gait
patterns that have been affected by deformity (usually in the form of contractures), muscle weakness, impaired motor control (including sensory loss and
spasticity) and pain (3). Any alteration
affecting one or more motion or timing
pattern can create a pathological gait
pattern. Even minor alterations can increase energy expenditure and progress to pathomechanical involvements.
Deviations to normal gait patterns
can be observed during both swing and
stance phases and require systematic
evaluation for assessment of functional
compensations and/or neuromuscular-skeletal factors. Functional compensations are voluntary posturings that attempt to substitute for specific motor
weaknesses and joint instabilities. It is
important to identify functional compensations from imposed mechanisms
for appropriate orthotic design and
therapeutic considerations.
Swing phase characteristics of pathological gait are summarized in Figure 3
, Figure 4
, Figure 5
, and Figure 6
, with identification of the
most commonly recognized functional
compensations and neuromuscular-skeletal factors. Beginning proximally
with pelvis and trunk involvement, observations should be made of sagittal,
coronal and transverse plane alignments. Greater disturbances or displacements of this proximal mass
(HAT) create increased demands on
the lower-limb segments and alignments to maintain dynamic balance
and stability. They also significantly increase energy costs. Functional compensations are evidenced by anterior,
posterior and lateral trunk leans. Pelvic involvement is primarily due to
neuromuscular factors (both tone-induced patterns or motor weaknesses)
but can also result from skeletal anomalies and distal instabilities.
Pathological hip joint involvements
are triplanar and are both compensatory and physical in nature. As with all
joints, skeletal anomalies can affect
both dynamic motion patterns as well
as stance phase stability, and thorough
assessment and identification of these
factors must be made (see Figure 4
).
Sagittal plane deviations of the knee
joint include excessive flexion and extension alignments during swing phase.
Excessive flexion may either assist in
ground clearance due to related factors
or may be the result of contracture or
flexor synergy (see Figure 5
).
The ankle joint rarely exhibits functional compensations during swing
phase as its alignment is critical for
ground clearance (see Figure 6
). Excessive plantarflexion makes ground
clearance difficult and induces more
proximal compensations while excessive dorsiflexion is rare and is most often an attempt to compensate when a
painful joint decreases hip or knee flexion.
Pathological gait deviations in stance
phase may be the result of functional
compensations or neuromuscular-skeletal factors. In conjunction with swing
phase deviations, observations can
identify "excessive vertical displacement of the COM, poor use of body
momentum, marked inefficiencies in
the transformations between kinetic
and potential energies, and increased
energy requirements" (4).
Beginning distally with the foot and
ankle, stance phase deviations can be
observed from weight acceptance
through forward progression and their
proximal joint and alignment implications properly identified. Functional
compensations are primarily found
with leg length discrepancies and pain-avoidance patterns. Proximal joint limitations might also impose compensatory alignments and compensatory
mechanisms such as vaulting for contralateral ground clearance during
swing (see Figure 7
). Neuromuscular
and skeletal factors are numerous and
individual evaluation and assessment is
critical. Tone-induced posturings and
contracture formation are common in
pathological gait, and specific muscle
weaknesses can also engender imbalances and therefore deviations.
Foot and ankle posturings will have a
direct effect on knee joint alignment
during weightbearing. Excessive posterior and anterior moments at the knee
will be created by excessive plantarflexion and dorsiflexion at the ankle,
respectively (see Figure 8
).
Hip joint stability during stance
phase is critical as it is the direct link
between the lower extremity and the
heavy HAT section. Even minor weaknesses evidenced at the hip can create
great displacement of the proximal
body mass and significantly alter
weightbearing and ground reaction
lines while increasing energy costs (see
Figure 9
). Functional compensations
for ankle and knee alignments can be
noted as well as neuromuscular factors
such as spasticity and specific weaknesses.
Maintenance of the proximal body
mass segment is directly related to hip
joint alignment as well as more distal
joint alignments and is necessary for
dynamic stability (see Figure 10
).
Gross displacements will increase energy costs but may also serve as functional compensations for other deficiencies
such as muscle weaknesses, distal contractures, leg length discrepancies or
painful joints.
Pathological gait patterns may significantly alter the magnitude of the lever
arm forces imposed on the lower extremities. Unaddressed, these forces
may abnormally stress ligamentous
structures with resulting laxities at the
midtarsal, subtalar and/or knee joints.
When unable to return to neutral joint
angulation alignment under static
weightbearing, these joint posturings
may signal the genesis of pathomechanical gait.
Pathomechanical GaitThe ERD-IRD Model in Pathomechanical Gait
Pathomechanics is a branch of physical
science that deals with static and dynamic forces and their abnormal effect
on a human body affected by neurological, muscular and skeletal disorders. As this relates to clinical gait assessment, a potential lower extremity
pathomechanical deformity is identified when a lever arm has changed
from the "normal" profile of the lower
limbs. Such a change is usually caused
by neuromuscular, velocity or balance
factors and results in excessive vertical
or horizontal displacement of the
COM. An actual lower-extremity pathomechanical deformity is identified
when the skeletal system is:
- unable to return to neutral joint
angulation alignment under full static
weightbearing at one or more of the
following joints: midtarsal, subtalar
and knee joints. This misalignment
usually results in excessive internal or
external transverse plane rotation of
the biomechanical axis of the talocrural
joint when the knee axis is aligned perpendicular to the line of progression.
- Altered structurally from surgery,
which results in actual skeletal lever
arm changes.
The evaluation process used in identifying potential and actual pathomechanical deformities that affect gait
should be time- and cost-effective, logical and relate mechanically to the skeletal structure of the human body in all
three planes of motion. With the notable exception of lever-arm alterations
in the structure of the skeleton (skeletal pathomechanics), most lower-extremity deformities are the result of ex
exessive internal or external transverse
plane rotation at the foot and ankle and
at the hip joint.
In human bipedal ambulation the
body mass advances in a theoretical
line of progression through a complex
sequential process of muscle- and gravity-powered joint rotations. The line of
progression is defined as the hypothetical path of the COM simplified by integrating the different movements of all
three perpendicular planes of reference into a single compound unit (5).
The External Rotary Pathway
The external rotary pathway (ERD) is
the biomechanical skeletal realignment
of a limb being maximally torqued externally in the transverse plane from
proximal to distal by muscle power under full weightbearing with the body in
the anatomical position. Reacting to
this external moment, the foot will simulate a supinated position, and certain
observed and inferred skeletal changes
will occur from distal to proximal (see
Figure 11
).
The Internal Rotary Pathway
The internal rotary pathway (IRP) is
the biomechanical skeletal realignment
of a limb being maximally torqued internally in the transverse plane from
proximal to distal by muscle power under full weightbearing with the body in
the anatomical position. Reacting to
this internal moment, the foot will assume a pronated position, and certain
observed and inferred skeletal changes
will occur from distal to proximal (see
Figure 12
).
The ERD-IRD Pathomechanical
Models
Alteration of functional lever arms in
the lower extremities from factors imposed by variations in the neuromuscular system often results in abnormally
magnified forces. When these forces
place constant and unrelieved tension
on the ligamentous structures of the
midtarsal, subtalar and knee joints,
especially under weightbearing and
with the body mass in motion, ligamentous laxity will often result and the ensuing pathomechanical deformity (ligamentous pathomechanics) will progress along one of the biomechanical
rotary pathways. When clinically identified, such a deformity is classified as verse plane but which subsequently
either an ERD or as an IRD whose primary plane involvement is the transverse plane but subsequently also involves deviations in both the coronal and sagital planes.
In ligamentous pathomechanics,
very few deformities' primary plane involvement is not the transverse plane.
These are called non-rotary deformities (NRD). They originate in the knee
joint (e.g., osteoarthritis) and develop
opposite angular compensations at the
foot and ankle (see Figure 13
).
Other pathomechanical exceptions
to the ERD-IRD model include foot
deformities distal to the midtarsal joint
such as ray deformities or hallux valgus. It should be noted that one of the
mechanical causes of hallux valgus is an
IRD.
An ERD is a pathomechanical lower-extremity skeletal joint angulation
deformity in which the tibia-fibula
structural unit rotates externally so
that each bone and joint follows the
established biomechanical external rotary pathway. To achieve plantigrade
position at midstance, there is some
compensatory forefoot pronation.
When there is 10 or more degrees of
calcaneal varus angulation relative to
the horizontal of the floor, full forefoot
compensatory pronation to achieve a
plantigrade position is not possible because of the skeletal limitation of the
foot (see Figure 14
).
An IRD is a pathomechanical lower-extremity skeletal joint angulation deformity in which the tibia-fibula structural unit rotates internally. The foot
almost always achieves plantigrade position as there is full forefoot compensatory supination. Usually ligamentous
laxity occurs at the midtarsal and subtalar joints and frequently also at the
knee joint. With a compromised anterior foot lever arm there is usually a
plantarflexion contracture at the talocrural joint with pathomechanical dorsiflexion occurring at the midtarsal
joint in stance phase. An IRD gait pattern is almost always a stance phase
deformity (see Figure 15
).
Pathomechanical Knee Involvement
In normal gait, transverse plane internal and external torque is transferred
from the talus directly to the tibia and
fibula and thus to the knee joint. For
example, supination of the foot and ankle under weightbearing will externally
rotate the talus transferring this torque
proximally to the knee joint with the
opposite being true for pronation and
internal rotation of the talus. This has
been previously described by Rose, Inman and Sarrafian (6,7)
As an ERD progresses, the hypothetical center of the ankle joint (talus)
is positioned posteriorly and laterally
from neutral. In addition, the talus has
externally rotated relative to the forefoot and to the LOP. This external
torque is transferred proximally to the
knee joint and, while the ligamentous
structures of the knee are intact, to the
hip joint. Due to this torque in the
transverse plane and to skeletal alignment, the knee is subjected to hyperextension and varum forces during single-limb stance. The possibility of a genu
recurvatum is created by the sustained
rigidity of the foot and ankle structures
which, combined with the body mass in
motion, can result in ligamentous laxity at the knee joint.
An IRD predisposes the knee joint
to internal rotary, flexion and valgum
forces. When accompanied by quadriceps weakness, the knee joint assumes
a position of hyperextension to prevent
joint collapse when the body mass is
static and frequently when it is dynamic. An IRD recurvatum is defined by the
ensuing knee ligamentous laxities and
will usually not progress significantly due
to the loss of foot and ankle rigidity from
ligamentous laxity at the midtarsal joint.
Such a recurvatum will develop perpendicular to the joint axis (determined by
the talus which is excessively internally
rotated) and proceed from anterior-medial to posterior-lateral.
A pathological gait can thus deteriorate into a pathomechanical gait when
ligamentous laxities result from an
IRD, ERD, NRD or skeletal pathomechanical deformity due to a progressively changing lever arm profile.
Evaluation of Pathomechanical
Deformities
Clinical assessment of pathomechanical
deformities requires a systematic
approach. Initiating treatment without
identifying the primary and secondary
involvements can lead to ineffective o
even damaging programs for the patient.
Information necessary for clinical
gait assessment is patient history, muscle/neurological evaluation, static
alignment, angulation measurements
dynamic alignment, pathological/pathomechanical conclusions and orthotic
recommendation.
Patient History
Considerations should be made regarding the age, height, weight, diagnosis.
prognosis, current ambulation limitations, date of onset, chief complaints,
realistic goals, current and past medications, "normal" ambulation ideals,
assistive devices, edematous conditions, activity level and other medical
problems. This information should be
specific to each patient so an appropriate and representative "ideal" patient
model can be formed.
Muscle/Neurological Evaluation
A muscle/neurological evaluation is
best provided by a physical therapist or
other trained medical professional.
This information will help identify generalized motor deficits, specific weaknesses/strengths, tone pattern involvements, proprioceptive deficits, range-of-motion limitations and coordination
limitations.
Static Alignment
During static alignment, assessment is
made of the skeletal integrity and
alignments of the entire body posturing. The patient is asked to stand in a
relaxed, comfortable position with
equal weight through both lower extremities. The patient should face
straight ahead with shoulders and pelvis squared. Assessment of static alignment should examine the skeletal
alignments of the foot and ankle complex, knee and hip as well as the posturing of the pelvis and trunk. IRD,
ERD or NRD classification can be made at this time.
Angulation Measurement
These measurements can be gathered
from the patient directly or assessed
from photographs. Measurements
must be acquired in the upright,
weightbearing position and relate to
only constant factor available-
gravity. This vertical reference line relates each specific segment of the human body in space independent of
proximal and distal components and is
used to document correction or monitor progression of a structural deformity.
Standing angulation measurements
should include calcaneal angulation in
the coronal plane, talocrural attitude in
the sagittal plane, knee attitude in the
coronal and sagittal planes, hip attitude in the coronal and sagittal planes,
sacral attitude in the sagital plane, and
pelvic attitude in the coronal plane.
Talocrural transverse plane rotation
is also important in establishing the degree of internal or external torque generated and dissipated throughout the
extremity.
Dynamic Alignment
Asking the patient to ambulate, in the
safety of parallel bars if necessary, the
clinician observes the dynamic relationship between all body parts. Clinical gait assessment is divided into two
major component parts: stance phase
and swing phase.
It is important to establish and verify
the inter-relationship of all body segments during both swing and stance.
Pathological/Pathomechanical
Conclusions
Pathological gait patterns, such as specific quadriceps weakness, can predispose a patient to the development of
pathomechanical deformities. Such deformities could progress as a result of
the typical compensatory posturing of
hip external rotation and sustained
knee extension. This compensatory
mechanism is unconsciously aligned to
rotate the knee axis externally relative
to the LOP while manipulating the
COM anteriorly to the knee joint during stance to provide stability against
collapse.
In the case of an identified skeletal
pathomechanical deformity, ligamentous laxities can often be expected. In
the pediatric population, ligamentous
laxities might lead to skeletal malformation if these structures develop and
ossify during growth in a misaligned
posturing. Often, neuromuscular deficits alter skeletal alignment and create
abnormally high forces to ligamentous
structures primarily at the midtarsal,
subtalar and knee joints. It is important to identify and remove potentially
damaging forces before they create ligamentous laxities and deformation. A
key factor in this process is predictability given skeletal structures, possible
joint alignments and planes of motion.
Orthotic Design and Recommendation
The end result of the clinical gait assessment procedure for the orthotist is
the determination of the orthotic design and recommendation. Orthotic
design takes the form of three-point
force systems specific to the joint angulation alignments, the planes of deviation and the necessary support due to
motor deficits.
Three-point force systems may be either structural or ground reaction in
nature. Structural three-point force
systems provide joint stability by physically bridging the joint in question. All
three-point force systems have in common the following elements:
- Point No. 1 is distal to the joint in
question and on the concave side of the
deformity
- Point No. 2 is at the joint in question and on the convex side of the deformity
- Point No. 3 is proximal to the joint
in question and on the concave side of
the deformity.
Three-point force systems incorporating ground reaction principles follow the same general format of force
application but do not structurally
ridge the joint in question. Ground reaction orthotics has been defined as
"a branch of orthotics in which an orthosis applies a stabilizing force to a proximal joint without structurally bridging
that joint, utilizing both mass in motion
and floor reaction as two of the three
forces in a three-point force system"
(8). It is in this manner that a foot orthosis can stabilize the subtalar joint in
the coronal plane without crossing the
subtalar joint, and an ankle-foot orthosis can effectively address a knee instability in the sagittal plane without
structurally bridging the knee joint.
With thorough assessment of the
structural deformation and motor deficits in mind, an orthotic design will incorporate the necessary three-point
force systems to effectively counteract
the deforming forces and prevent progression. Most orthotic designs are a
combination of structural and ground
reaction three-point force systems used
in series.
Deanna J. Fish, CPO, is marketing director at Oregon Orthotic System Inc., 2280 Three Lakes Road, S.E., Albany, OR 97321.
Jean-Paul Nielsen, CP, is CEO, president and clinical consultant at Oregon Orthotic System Inc., 2280 Three Lakes Road, S.E., Albany, OR 97321.
References:
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and The Physical Therapy Department of
Rancho Los Amigos Medical Center, 1989.
California: The Professional Staff Association.
- Perry J. Gait analysis: normal and pathological function 1992. New Jersey, SLACK
Inc.
- Whittle MW. Gait analysis: an introduction 1991. Oxford: Butterworth-Heinemann.
- Gage JR. An overview of normal walking. Instructional Course Lecture
1990;39:291-303.
- Steindler A. Kinesiology of the human
body under normal and pathological conditions 1955. Illinois: Charles C. Thomas.
- Rose GK. Correction of the pronated
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- Sarrafian SK. Functional characteristics
of the foot and plantar aponeurosis under
tibiotalar loading 1987; Foot & Ankle:8(1):4-18.
- Adapted from Nielsen JP. Fish Di. Unpublished course material for OOS-l Basic
Seminar in Pathomechanical Deformities.
Lower Extremity Derotational Orthotics:
ERD - IRD Model 1991.
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