Little r^l II I
5. The whole leg is externally rotated during the swing phase 6. There is an absence of reciprocal arm swinging
These differences in gait mature at different rates. The characteristics numbered (3), (4) and (5) in the above list have changed to the adult pattern by the age of two years, and (1) and (6) by the age of four. The cadence, stride length and velocity continue to change with growth, reaching normal adult values at around the age of 15 years.
Most children commence walking within three months of their first birthday. Prior to this, even small babies will make reciprocal stepping motions if they are moved slowly forwards while held in the standing position with their feet on the ground. However, this is not true walking, as there is little attempt to take any weight on the legs.
Figure 2.24, which is based on Sutherland et al. (1988), shows the average sagittal plane motion at the hip, knee and ankle joints in 49 children between 11 and 13 months. It should be compared with Fig. 2.5, which shows the same parameters for adult gait. Sutherland et al. do not give the timing of mid stance, heel off or mid swing.
The pattern of hip flexion and extension differs from that in adults in
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Fig. 2.24 Sagittal plane hip, knee and ankle angles in one-year-old children.
Sign conventions as in Fig. 2.5. (Sutherland et al., 1988.)
Normal Gait 87 that the degree of extension is reduced, and the hip does not remain flexed for so long at the end of the swing phase.
The knee never fully extends, but this is seen at all ages in Sutherland's data, and may reflect the method of measurement. There is some stance phase flexion in infants, but it is both smaller in magnitude and earlier than in adults. (It should be noted that most adults show more stance phase flexion than is seen in Fig. 2.5.) The flexion of the knee in the swing phase is also somewhat reduced at the age of one year.
Initial contact in small children is by the whole foot, heel contact being replaced by foot flat. The ankle is plantarflexed at initial contact, and remains so into the early stance phase, in contrast to the adult pattern, in which the ankle is approximately neutral at heel contact, but moves rapidly into plantarflexion. The pattern of dorsiflexion followed by plantarflexion through the remainder of the stance phase is essentially the same at all ages.
Since children are smaller than adults, it is not surprising that they walk with a shorter stride length and at a lower velocity. Sutherland et al.
(1988) showed that stride length is closely related to height, and that the ratio of stride length to stature is similar to that found in adults. The change in stride length with age mirrors the change in height, showing a rapid increase up to the age of four years, and a slower increase thereafter. Todd et al. (1989) showed the relationships between the height of children and the general gait parameters. Small children walk with a rapid cadence, the mean at the age of one being about 170 steps per minute. It reduces with age, but is still around 140 steps per minute at age seven, which is well above the average adult values of 113 for men and 118 for women. The higher cadence partly compensates for the short stride length, and the velocity ranged from 0.64 m/s at age one to 1.14 m/s at age seven, compared with the typical adult values of 1.46 m/s for males and 1.30 m/s for females. Sutherland did not report on the gait of children beyond the age of seven, and did not distinguish between the results from boys and girls. Appendix 1 gives the normal ranges for the general gait parameters in children, derived in part from Sutherland's data.
As can be seen in Fig. 2.24, the swing phase occupies a smaller proportion of the gait cycle in very small children than in adults, which minimizes the time spent in the less stable condition of single legged stance. The relative duration of the swing phase increases with age, reaching the adult proportion around the age of four years. There is symmetry between the two sides at all ages. Sutherland et al. (1988) related the width of the walking base to the width of the body at the top of the pelvis, giving a slightly confusing 'pelvic-span:ankle-spread' ratio.
88 Gait Analysis: An Introduction
Changing the measurement units for the sake of clarity, the walking base is about 70 per cent of the pelvic width at the age of one year, falling to about 45 per cent by the age of three and a half, at which level it remains until the age of seven. An average value for adults is not readily available, but it is probably less than 30 per cent.
At the very youngest ages, the EMG patterns showed that there is a tendency to activate most muscles for a higher proportion of the gait cycle than in adults. With the exception of the triceps surae, adult patterns are established for most muscles by the age of two years.
Sutherland et al. (1988) found that children could be divided into two groups depending on whether the triceps surae was activated in a prolonged (infant) pattern or the normal (adult) pattern. Below the age of two years, over 60 per cent of the children showed the infant pattern; the proportion dropped to below 30 per cent by the age of seven. They speculated that this might relate to delayed myelination of the sensory branches of the peripheral nerves.
Gait in the elderly
A number of investigations have been made of the changes in gait which occur with advancing age, especially by Murray et al. (1969), who studied the gait of men up to the age of 87. The description which follows is confined to the effects of age on free-speed walking, although Murray et al. also examined fast walking. A companion paper (Murray et al., 1970) studied the gait of women up to age 70. It did not provide as much information on the effects of age, but generally confirmed the observations made on males.
The gait of the elderly is subject to two influences - the effects of age itself, and the effects of pathological conditions such as osteoarthritis and parkinsonism, which become more common with advancing age.
Providing patients with such conditions are carefully excluded, the gait of the elderly appears to be simply a 'slowed down' version of the gait of younger adults. Murray et al. (1969) were careful to point out that 'the walking performance of older men did not resemble a pathological gait.' Typically, the onset of age-related changes in gait takes place at 60 to 70 years of age. There is a decreased stride length, a variable but generally decreased cadence, and an increase in the walking base. Many other changes can also be observed, but most of them are secondary to these three. The velocity, being the product of stride length and cadence, is almost always reduced in elderly people. Appendix 1 gives normal ranges for the general gait parameters up to the age of 80 years.
Normal Gait 89
Fig. 2.25 Body position at right heel contact in older men (left) and younger men (right) (Murray et al, 1969.)
Some of the differences between the gait of the young and the elderly are apparent in Fig. 2.25, which is taken from Murray et al. (1969).
These authors suggested that the purpose of the gait changes in the elderly is to improve the security of walking. Both decreasing the stride length and increasing the walking base make it easier to maintain balance while walking. Reducing the cadence leads to a reduction in the percentage of the gait cycle for which there is only single limb support, since the increase in cycle length is largely achieved by lengthening the stance phase and hence the double-support time.
Changes in the angular excursions of the joints in the elderly include a reduction in the total range of hip flexion and extension, a reduction in swing phase knee flexion, and reduced ankle plantarflexion during the push off. However, all of these depend on both cadence and stride length, and are probably within normal limits if these factors are taken into account. The vertical movement of the head is reduced and its lateral movement increased, probably secondary to the changes in stride length and walking base, respectively.
The trajectory of the toe over the ground is modified in old age, giving an improved ground clearance during the first half of the swing phase.
This is probably another mechanism for improving security. The heel rises less during the push off phase, and the foot attitude is closer to the
90 Gait Analysis: An Introduction
horizontal at heel contact, both of these changes being related to the reduction in stride length. There is also an increase in the angle of toe out in elderly people, and changes in the posture and movements of the arms, the elbows being more flexed and the shoulders more extended.
The reasons for these differences are not known.
The dividing line between normal and abnormal may be difficult to define in elderly people. A condition known as 'idiopathic gait disorder of the elderly' has been described, which is essentially an exaggeration of the gait changes which normally occur with age, and is characterized by a cautious attitude to walking, with a low cadence, a short stride length, and an increased step-to-step variability.
3
Pathological Gait
Although some variability is present in normal gait, particularly in the use of the muscles, there is a clearly identifiable 'normal pattern' of walking, and a 'normal range' can be defined for most of the measurable parameters. Pathology of the locomotor system frequently produces abnormal patterns of movement or applied force. Some of these abnormalities can be identified by eye, but others can only be identified by the use of appropriate measurement systems.
In order that a person can walk, the locomotor system must be able to accomplish four things:
1. Each leg must be able to support the body weight without collapsing 2. Balance must be maintained, either statically or dynamically, during
single leg stance
3. The swinging leg must be able to advance to a position where it can