Early Development and Attainment of
Normal Mature Gait
Mary Keen, MD
ABSTRACT
This article describes the process of development of normal human locomotion, major neuromotor and musculoskeletal factors that may affect this process, and normal physiological variations.
Introduction
The human body is built for motion.
Forty percent of adult body mass is
muscle with proportionally more in the
lower extremities. Muscles and bones
are motors and levers designed to allow
movement in many planes. Muscles are
necessary not only for propulsion but
also for deceleration and shock absorption.
The human body also is designed for
efficiency in movement. Because of the
unique design of the human body for
bipedal locomotion, relaxed standing
requires minimal energy, and human
beings naturally assume a rate of speed
of locomotion that is most efficient for
them. Such efficiency requires integration of movement of many joints and
muscles. Thus, a large percentage of
the human brain is dedicated to gross
and fine motor coordination and balance.
Normal gait is cyclic; that is, it involves movements in space that are repeated over and over. For descriptive
and analytic purposes, gait has been
divided into two phases: the stance
phase and swing phase, and the phases
have been further divided into specific
points. These phases and points are
uniformly present in normal gait (see
Figure 1
).
Human locomotion also has idiosyncratic characteristics with unique aspects apparent in every individual. We
can identify family and friends by their
gaits. However, an individual's gait
also varies according to speed, mood,
footwear and fatigue.
Human locomotion is also affected
by changes in development such as
physiological processes affecting neuromotor control, growing and maturing body segments, variable rotation of
limbs and joints about an axis of motion, and changes in posture. The attainment of locomotor skills is a complicated process dependent upon an intact neuromotor and musculoskeletal
system.
Neuromotor Development
Humans develop all the brain cells they
will ever have by 20 weeks of intrauterine life. Interneurons appear and reproduce to interconnect brain cells until about age one. The process of myelination takes several years and is completed in a cephalad to caudal (head to
tail) direction. There is much individual variation in the rate of development of neuromotor control.
Early neuromotor maturation is
manifested by the suppression of primitive reflexes and the appearance of
postural responses (see Figure 2
and
Figure 3
). Abnormalities in either the primitive reflexes or postural responses can
reflect a disorder in the central or peripheral nervous system (1).
Primitive reflexes are naturally present in the newborn and infant younger
than 6 months. They are never normally obligatory or persistent; rather, infants move in and out of these patterns
until the patterns are gradually completely suppressed. Postural responses,
on the other hand, gradually appear as
the primitive reflexes disappear. Postural responses are under volitional
control and are incorporated naturally
into movement and locomotion. The
evolution of primitive reflexes and postural responses, also occurs proximal
to distal (1).
The processes of suppression of the
primitive reflexes and integration of
postural responses vary greatly. However, persistence of multiple primitive
reflexes, failure to develop normal postural responses or asymmetry in the
manifestation of either the infantile reflexes or postural responses are signs of
abnormal neuromotor development
and may indicate neuromotor dysfunction. Causes of persistent infantile reflexes and delayed or absent postural
responses are listed in Figure 4
and Figure 5
.
Although deviations from normal
may be signs of neuropathology, many
children "outgrow" distinctly abnormal neurologic examinations. In the
Collaborative Perinatal Project of the
National Institute of Neurological and
Communicative Disorders and Stroke,
more than 37,000 children were examined prospectively and serially by experienced examiners. Fifty-one percent
of children with "definite" cerebral
palsy and 96 percent of children suspected of having cerebral palsy had
normal neuromotor exams at age 7.
Therefore, abnormal neuromotor examinations in early childhood may normalize. However, these children are at
higher risk for mental retardation.
Effect of Neuromotor Dysfunction
on Motor Milestones
Persistence of primitive reflexes will interfere with volitional changes in posture and tone necessary for locomotion. The association of persistent infantile reflexes and delayed ambulation in infants and children with cerebral palsy has been well documented.
Postural responses, on the other hand,
are critical for maintaining balance in
the upright position first in sitting, then
in standing and achieving locomotion
skills of walking and running.
If primitive reflexes are not suppressed and postural responses do not
appear in the normal time range, a
child is likely to experience delays in
achieving motor milestones (2). Figure
6
lists some basic gross motor milestones and the usual age at which they
are attained (1).
A large range of normal variation
exists, and a delay in gross motor milestones does not necessarily indicate
neuropathology. An examination of
404 late walkers (not taking six steps
independently at 18 months) found pathology in only 32 percent (3). Among
infants who were small for gestational
age or who required admission to the
special-care nursery, abnormalities
were found in 56 percent. Of these,
approximately one-third had cerebral
palsy, one-third global delay, and onethird had other neurological or congenital disorders (4).
Musculoskeletal Development
Musculoskeletal development occurs
concurrent with neuromotor development (1). During intrauterine growth
and development the spinal column assumes a 'c" shape and the limbs a
flexed and internally rotated posture.
In the first weeks of extrauterine life,
this predominant flexor tone relaxes,
and an infant assumes a more neutral F
posture. The cervical "c" curve flattens
for sitting at 6 to 7 months and reverses
to a lordosis for standing by 9 to 12
months.
As a result of intrauterine crowding,
infants are born with mild joint contractures and curves in long bones that
resolve spontaneously after birth.
Joints also rotate with growth and development. The rate and extent of
these physiological musculoskeletal
changes vary considerably in normal
children, and during the process of
growth and maturation these physiological variations may cause parental
concern.
Common Developmental
Orthopedic Concerns
Pes planus or flat feet is usually a normal variant. Most children have apparent flat feet until ages 3 to 5 when baby
fat diminishes and ligaments tighten.
Hypermobile flat feet may require orthopedic shoes or orthoses to prevent
overstretching of ligaments (5).
Toe walking. Some children learn to
walk with a toe-walking pattern instead
of the normal foot flat during stance.
Approximately 30 percent have a family history of toe walking, and the condition is more common in boys than
girls. Toe walking can be caused by
such neurological conditions as cerebral palsy; idiopathic toe walking usually resolves sometime during childhood. Stretching exercises are indicated when shortening of the gastrocsoleus muscle groups occurs. Serial casts
and dynamic splints are sometimes
used, and surgery is rarely necessary.
Intoeing. Major causes of intoeing
include femoral anteversion, internal
tibial torsion and problems of the foot,
including metatarsus adductus, clubfoot and dynamic intoeing.
Femoral anteversion is a normal anatomic condition. Excessive anteversion
is generally due to ligamentous laxity
and usually resolves by age 5.
Internal tibial torsion is also a normal
anatomic variant that generally corrects spontaneously with growth. Night
splints may accelerate correction. Surgery is rarely required.
Metatarsus adductus is the most common congenital foot deformity. Five to
10 percent of cases are associated with
dysplasia of the hip. If the foot is not
passively correctable (by stretching),
serial splinting or casting is necessary.
Surgical release is required when rigid
metatarsus adductus persists after two
years.
Outtoeing, like intoeing, has several
causes: external rotation contracture
of the hip, which usually resolves spontaneously; femoral retroversion in
which the patella faces outward (very
rare); and external tibial torsion,
which is usually a compensatory mechanism for excessive femoral anteversion.
Bowlegs or genu varus is a physiological condition and corrects spontaneously by age 2. If the bowing is greater
than 15 degrees, splinting with a Denis
Browne bar may be indicated. Blount's
disease or progressive bowing, or bowing beyond age 2, requires splinting
and/or surgery to prevent damage to
growth plates.
Knock knees or genu valgus is classified as apparent, physiologic or pathologic. Most cases are physiologic and
resolve before age 7. Pathologic genu
valgus caused by juvenile rheumatoid
arthritis or paralysis may require surgery.
Maturation of Gait
It takes several years for a mature gait
pattern to evolve. Characteristics of a
mature gait pattern include a narrow
base of support, smooth movements
with minimal oscillations of the center
of gravity and reciprocal arm swing.
Most practitioners agree a mature
gait is present in normal children by
age 5. However, after analyzing 186
normal children, Sutherland concluded
a mature gait pattern is well established
in most children by age 3 (6). The criteria he used included duration of single-limb stance, walking velocity, cadence,
step length and ratio of pelvic span to
ankle spread.
Children at age 1 have much higher
step frequency (180 steps/minute) than
adults. They do not have reciprocal
arm swing; arms are held in "high
guard." The hip joint remains externally rotated throughout the gait cycle,
and the knee remains flexed. The ankle
is in plantarflexion at heelstrike, and
dorsiflexion during swing phase is diminished. Hip flexion, pelvic tilt and
hip abduction are all increased during
swing phase. Single-limb stance is reduced, and the base of support is wide.
At 18 months, nearly all children
walk with heelstrike and more than 70
percent have reciprocal arm swing.
The base of support narrows significantly but remains wider than a mature
gait pattern.
Two-year-old children have less pelvic tilt, abduction and external rotation
of the hip. Nearly 80 percent have reciprocal arm swing, and knee flexion
during stance is more pronounced than
in older walkers. Duration of single-limb stance is less than 34 percent, and
the base of support remains wide although it has narrowed somewhat.
In 3-year-old children, duration of
single-limb stance is about 35 percent.
Ninety percent have reciprocal arm
swing. The base of support is proportionately similar to adults. Differences
from a mature adult gait include a
greater knee flexion wave during
stance and slightly increased pelvic rotation, hip joint rotation and hip abduction. However, children have
achieved an adult pattern of joint angles throughout the gait cycle by this
stage.
The gait of a 7-year-old child has the
same differences from an adult's gait as
a 3-year-old's does-but to a lesser degree. Adult cadence, step length and
velocity cannot be achieved until adequate growth occurs. Duration of single-limb stance in a 7-year-old is about
38 percent. (In adults, duration is
about 39 percent).
Summary
Human locomotion is a complicated
process. The attainment of normal gait
in humans is also a complicated process, involving not only physical maturation, but learning. It is not simply the
result of inborn reflexes, although re
flexes contribute to balance and efficiency. It requires an intact musculoskeletal system as well as an intact neuromotor system.
Mary Keen, MD, is board certified in physical medicine and rehabilitation, orthopedics and pediatrics. She is clinical assistant professor of pediatrics and orthopedics at Loyola University Medical Center, 2160 S. First Ave., Maywood, IL 60153.
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