Gait and Posture 11 (2000) 224 – 232
www.elsevier.com/locate/gaitpost
Common abnormal kinetic patterns of the knee in gait in spastic
diplegia of cerebral palsy
Chii-Jeng Lin a, Lan-Yuen Guo b,c, Fong-Chin Su b,*, You-Li Chou b, Rong-Ju Cherng d
b
a
Department of Orthopaedic Surgery, National Cheng Kung Uni6ersity, Tainan, Taiwan
Motion Analysis Laboratory, Institute of Biomedical Engineering, National Cheng Kung Uni6ersity, 1 Uni6ersity Road, Tainan 701, Taiwan
c
Department of Physical Therapy, Tzu Chi College of Technology, Hualian, Taiwan
d
Department of Physical Therapy, National Cheng Kung Uni6ersity, Tainan, Taiwan
Received 13 May 1999; received in revised form 30 October 1999; accepted 29 December 1999
Abstract
We studied the kinetic characteristics of the knee in patients with spastic diplegia. Twenty three children with spastic diplegia
were recruited and had their 46 limbs categorised into the following four groups: jump (n= 7), crouch (n= 8), recurvatum (n =14)
and mild (n=17). In the crouch pattern, the patients usually had a larger and longer lasting internal knee extensor moments in
stance suggesting that rectus femoris had a relatively high activation. In the recurvatum pattern, the internal knee flexor moment
was large and long lasting in stance. The biceps femoris showed less activity on EMG although the knee flexor moment was large
and we concluded that the soft tissue behind the knee joint provided this flexor moment. In the jump knee pattern there was
abnormal power generation at the knee and ankle joints in initial stance, which did not contribute to normal progression but aided
upward body motion. In the mild group the kinetic data was similar to that seen in normal children. Knowledge of kinetic
patterns in these patients may help in their subsequent management. © 2000 Elsevier Science B.V. All rights reserved.
Keywords: Cerebral palsy; Spastic diplegia; Gait analysis; Kinetics; Moments; Powers
1. Introduction
Acquisition of kinetic data requires more complicated procedures than for collection of kinematic data
[1 – 8] but should provide a better understanding of
pathological gait. A joint moment represents the body’s
internal response to an external load [1 – 8]. During
normal gait, the influence of soft tissues, other than
muscles that are primary motion generators, on joint
moment generation is minimal. However, in abnormal
gait, the influence of soft tissue contracture on joint
moments may become substantial and can give misleading information about moment and power curves. In
such circumstances, dynamic EMG is important to
differentiate the cause of the moment. If the joint
agonist is not active on EMG, the moment could be
produced by joint capsule and ligamentous structures
* Corresponding author. Tel.: + 886-6-2757575, ext. 63422; fax:
+886-6-2343270.
E-mail address: [email protected] (F.-C. Su)
[6,7]. Power is defined as the work performed per unit
of time and may be used to document the net energy
absorption or generation of the muscles [3–8]. More
recently, joint kinetics, specifically joint moments and
joint powers, have been available as an additional tool
in the assessment of pathological gait [9–22].
In 1993, Sutherland and Davids classified the common gait abnormalities of the knee in cerebral palsy
(CP) into four types: jump, crouch, recurvatum, and
stiff [23]. Jump knee gait was characterised by increased
knee flexion in early stance phase, through initial double support, with correction of the knee wave to normal
or near normal extension in mid-stance and late-stance.
In crouch gait, there was increased knee flexion through
the stance phase, with variable alignment in swing
phase. Recurvatum knee gait described increased knee
extension in mid-stance and late-stance phase, with
variable knee motion in the swing phase. In comparison
to the three gait patterns in stance phase they characterised stiff knee gait by a decreased dynamic range of
motion of knee in swing phase.
0966-6362/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 6 6 - 6 3 6 2 ( 0 0 ) 0 0 0 4 9 - 7
C.-J. Lin et al. / Gait and Posture 11 (2000) 224–232
Though the grouping of such gait abnormalities by
kinematics is useful [23 – 28], the kinetic patterns were
not been described. The goal of this study was therefore
to identify and investigate the kinetics of these abnormal gait patterns in stance phase in diplegic CP.
2. Method
Twenty three patients (16 boys, seven girls, mean age
9 years) with spastic diplegia from CP were studied.
None had been operated on previously.
The laboratory was equipped with an Expert Vision
motion analysis system (Motion Analysis Corp., Santa
Rosa, CA, USA), integrated with three Kistler force
plates Type 9281B, Kistler Instrument Corp., Winterhur, Switzerland) and a MA-100 electromyography system (Motion Lab System, Inc., L.A., USA). The
motion analysis system included six CCD cameras, two
VP320 video processors, SUN workstation, trigger and
21 pieces of 3/4–1 inch reflective markers. Three Kistler
force plates were mounted on a 10.7 ×2.05-m walkway.
Two of them were 60×40 cm in size, and the other was
50 × 50 cm. There was additional accessory equipment,
including three preamplifiers, two AD converters (MP
280) and one 486 IBM compatible personal computer.
The electromyography (EMG) system comprised of a
backpack, interface unit and ten pre-amplified surface
electrodes.
Twenty one reflective markers were placed on each
subject based on the Helen – Hays marker set. The
motion analysis system was synchronised with three
force plates and the EMG system during data collection. The subjects were asked to walk at self-selected
speed after several trials. The force plates were concealed and the procedure was video taped for later
review. At least five successful trials were collected and
stored. The sampling rate of the cameras was 60 Hz.
225
The sampling rates of the EMG and force plates were
1000 Hz. The anthropometric data of each subject were
also measured and used for calculation of joint angles,
joint moments and joint powers.
The reflective markers locations were used to define
the co-ordinate system of linkage. OrthoTrak II software (Motion Analysis Corp., Santa Rosa, CA, USA)
was used to calculate the joint angles, joint reaction
forces, joint moments and joint powers of lower extremity in gait cycle. Three normalised (100%) gait
cycles for each subject were averaged before gait
parameters could be determined.
We divided the gait cycle into five gait events: heel
strike (HS), opposite toe off (OTO), opposite heel strike
(OHS), toe off (TO) and next heel strike after the
method of Sutherland [29]. The kinematic and kinetic
data at each gait event and their maximum and minimum, beside the curves, was analysed statistically. We
separated the gait patterns of the knee into four groups:
mild, crouch, recurvatum and jump based on the knee
kinematic patterns. The mild group was defined as
those who walked better than the other three groups
and those without specific knee kinematic patterns. The
normal data was elicited from the OrthoTrak II.
A one-way ANOVA was used to determine the differences in ground reaction force, moment and power
characteristics in the hip, knee and ankle between the
four groups and Tukey’s post-hoc test was used to
determine the significance between each pair of the four
groups.
3. Results
The gait patterns of 46 limbs in 23 patients were
divided into four groups, mild knee (n = 17), crouch
knee (n= 8), recurvatum knee (n = 14), and jump knee
(n= 7) basd on the knee kinematic patterns.
3.1. Sagittal plane joint angles
3.1.1. Knee
The sagittal-plane motion of the knee joint (Fig. 1) in
the four groups demonstrated specific characteristics. In
the initial stance phase, crouch and jump groups had
increased flexion. Throughout the whole stance phase,
only the crouch group had persistently increased knee
flexion while the flexion angles returned to almost
normal range in the jump group. The recurvatum knee
group, on the contrary, had increased knee extension in
mid-and late-stance phase.
Fig. 1. Mean sagittal plane knee motion of four cerebral palsy
groups.
3.1.2. Hip
The hip joint angle curves are shown in Fig. 2. The
crouch group showed excessive hip flexion during the
entire gait cycle.
226
C.-J. Lin et al. / Gait and Posture 11 (2000) 224–232
Fig. 2. Mean sagittal plane hip motion of four cerebral palsy groups.
3.1.3. Ankle
The curve patterns of ankle joint angle had their own
characteristics (Fig. 3) in different groups. The crouch
group showed excessive ankle dorsiflexion during the
whole stance phase, comparing with the normal children. Both jump and crouch groups had excessive
dorsiflexion during initial contact. The ankle motion
shifted to plantarflexion pattern in the jump group
while in the crouch group remained in a dorsiflexion
pattern. The recurvatum group demonstrated excessive
plantarflexion during the whole stance phase.
3.2. Vertical ground reaction force
The curve patterns of ground reaction force (GRF)
had their own characteristics (Fig. 4) in different
groups. The difference could be observed in loading,
first peak, valley, second peak and unloading. The jump
knee group had the most exaggerated pattern, including
rapid loading, high first peak (P B 0.0001), deep valley,
moderate second peak and normal unloading phase.
Fig. 3. Mean sagittal plane ankle motion of four cerebral palsy
groups.
Fig. 4. Mean vertical ground reaction forces of four cerebral palsy
groups.
The crouch group had the flattest pattern between the
first and second peaks. The valley was not apparent
during weight transmission period in this group. The
mild and recurvatum group had GRF curves similar to
the crouch group, though the changes were relatively
moderate.
3.3. Sagittal plane joint moments
3.3.1. Hip
The hip joint moments are shown in Fig. 5. All CP
groups had excessive torque at the hip. The crouch
group had the greatest extensor moment than the other
three groups in initial stance and mid-stance. In addition, the jump group tended to have the highest flexor
moment in terminal stance and pre-swing.
3.3.2. Knee
The differences of joint moments between groups
were the most significant at the knee joint (Fig. 6). The
crouch group had the greatest extensor moments
throughout the stance phase. The recurvatum group, on
the contrary, exhibited excessive flexor moments
Fig. 5. Mean hip joint moments of four cerebral palsy groups.
C.-J. Lin et al. / Gait and Posture 11 (2000) 224–232
227
Table 1
Knee joint momentsa at specific gait events and its peak values
Knee moment, N m/kg flexor (+)/
extensor (−)
Mild (n= 17)
Crouch (n = 8)
Heel strike
Opposite toe off
Opposite HS
Toe off
Heel strike
Maximum knee flexion
Maximum knee extension
0.04
−0.39
−0.05
−0.02
0.09
0.27
−0.47
−0.14
−0.68
−0.58
−0.06
0.14
0.20
−0.84
(0.37)
(0.26)
(0.13)
(0.04)
(0.04)
(0.13)
(0.27)
(0.38)
(0.22)
(0.39)
(0.13)
(0.06)
(0.05)
(0.23)
Recurvatum (n = Jump (n = 7)
14)
F valueb
0.07
0.08
0.08
−0.03
0.08
0.45
−0.21
1.91
18.64*
18.70*
0.88
8.72*
6.66**
16.13*
(0.20)
(0.27)
(0.11)
(0.06)
(0.03)
(0.20)
(0.23)
−0.28
−0.70
−0.22
0.00
0.17
0.20
−0.88
(0.44)
(0.32)
(0.17)
(0.06)
(0.03)
(0.07)
(0.17)
Post-hocc
R\M,C,J
R\J,C M,J\C
J\M,R C\R
R\M,J,C
R\M,C,J M\C,J
a
Means and S.D. in parenthesis.
Statistic was done with one-way ANOVA.
c
Tukey’s post-hoc test was used to determine the significance between each pair of the four groups.
* PB0.001;
** PB0.01.
b
throughout the stance phase with two peaks at OTO
and OHS. The jump group had the greatest extensor
moment in the loading response, a rapid decrease at
mid-stance and second peak at OHS.
Statistically, at OTO, there were significant differences between the four groups in knee joint moment
(P B 0.05, Table 1). In this study, the moments described are internal moments. The recurvatum group
had knee flexor moment, 0.08 N m/kg, while the crouch
and jump groups had extensor moments, 0.68 and 0.70
N m/kg, respectively. At OHS, there were significant
differences in knee joint moment between the four
groups (P B 0.05). While the recurvatum group was
dominated by knee flexors, the other three groups were
knee extensor dominant. In addition, knee extensor
moment of crouch group was significantly greater than
the jump and mild groups (P B0.05).
There were significant differences between the four
groups in the maximum knee flexor moment (PB0.05).
The joint moment of the recurvatum group, 0.45 N
m/kg, was significantly greater than the other three
Fig. 6. Mean knee joint moments of four cerebral palsy groups.
groups (PB0.05). There were also significant differences between the four groups in the maximum knee
extensor moment (P B 0.05). The maximum knee extensor moment of the crouch and jump groups were
significantly greater than those of the other two groups
(PB 0.05).
3.3.3. Ankle
The moment curves at the ankle joint are shown in
Fig. 7. The crouch group had a rapidly increasing and
constantly large plantar–flexor moment throughout
stance phase. The jump knee group showed a rapidly
increasing plantar–flexor moment at loading response,
a rapid decrease at mid-stance and an unusual second
increase at terminal stance. The mild group demonstrated normal dorsiflexor/plantar –flexor moments in
the whole of stance, except for an initial rapid plantar–
flexor moment increase at loading.
At OTO, there were statistically significant differences between the four groups in ankle joint moment
(PB 0.05, Table 2). The plantar–flexor moment of the
jump and crouch groups increased rapidly. During
single limb stance, the crouch group maintained high
Fig. 7. Mean ankle joint moments of four cerebral palsy groups.
228
C.-J. Lin et al. / Gait and Posture 11 (2000) 224–232
Table 2
Ankle joint momentsa at specific gait events and its peak values
Ankle moment, N m/kg dorsiflexion
(+)/plantar flexion (−)
Mild
(n = 17)
Crouch
(n = 8)
Heel strike
Opposite toe off
Opposite HS
Toe off
Heel strike
Maximum ankle dorsiflexion
Maximum ankle plantar flexion
0.08
−0.34
−0.81
−0.11
0.01
0.13
−1.00
−0.12
−0.67
−0.71
−0.07
0.01
0.02
−0.90
(0.36)
(0.28)
(0.19)
(0.11)
(0.02)
(0.34)
(0.28)
Recurvatum
(n = 14)
(0.08)
(0.34)
(0.25)
(0.14)
(0.00)
(0.01)
(0.26)
−0.14
−0.44
−0.53
−0.06
0.01
0.02
−0.79
(0.12)
(0.16)
(0.31)
(0.09)
(0.00)
(0.02)
(0.21)
F valueb
Jump
(n = 7)
−0.16
−0.66
−0.48
−0.02
0.01
0.08
−0.93
(0.20)
(0.39)
(0.28)
(0.05)
(0.00)
(0.13)
(0.34)
2.68
3.30*
3.61*
1.13
0.43
0.78
1.39
Post-hocc
R\M
a
Means and S.D. in parenthesis.
Statistic was done with one-way ANOVA.
c
Tukey’s post-hoc test was used to determine the significance between each pair of the four groups.
* PB0.05.
b
torque value in plateau shape, but the jump group
demonstrated a sine wave phenomenon. At OHS, there
were significant differences between the four groups
(P B 0.05). The plantar – flexor moment of the mild
group, 0.81 N m/kg, was significantly greater than that
of the recurvatum group was (P B0.05).
3.4. Joint powers
The differences of the power curve at the hip between
groups, similar to the moment curves, were not as
significant as that at the knee joint (Fig. 8). For the
sagittal plane hip power, the jump knee group had
greater absorption at terminal stance. Its maximum
absorption power, 1.09 W/kg, was significantly greater
(P B 0.05) than those of the mild, crouch, and recurvatum groups, 0.36, 0.39, 0.48 W/kg, respectively (Table
3).
For the knee power (Fig. 9), the jump knee group
had a dramatically large generation at initial stance and
excessive absorption power at pre-swing. Its maximum
generation power is significantly greater (P B 0.05) than
the other three groups with the value up to 1.88 W/kg
(Table 4). Statistically, at OTO, there were significant
Fig. 8. Mean hip joint powers of four cerebral palsy groups.
differences between the four groups in knee joint power
(PB 0.05). The joint power of the jump group, 1.24
W/kg, was significantly larger than the other three
groups (PB 0.05). At OHS, there were also significant
differences between the four groups in knee joint power
(P B 0.05). The absorption power of the crouch group,
0.63 W/kg, was significantly greater than that of the
recurvatum groups (P B 0.05).
The ankle power is shown in Fig. 10. The jump
group showed excessive absorption power in initial
contact and a premature generation of power at the
mid-stance phase. Except the mild group, the other
three groups had larger absorption powers in early
stance. Interestingly, all four CP groups were able to
generate sufficient powers at push off. At push-off, the
mild group had a larger power generation, 1.21 W/kg,
than in the other three groups, 0.7–0.9 W/kg (Table 5).
3.5. EMG
3.5.1. Gastrocnemius
All the abnormal knee groups, except the mild group,
demonstrated excessive firing amplitude of gastrocnemius immediately after initial contact (Fig. 11). In
contrast, the mild group showed slowly increasing firing
Fig. 9. Mean knee joint powers of four cerebral palsy groups.
C.-J. Lin et al. / Gait and Posture 11 (2000) 224–232
229
Table 3
Hip joint powersa at specific gait events and its peak values
Hip power, W/kg generation
(+)/absorption (−)
Mild
(n= 17)
Crouch
(n= 8)
Recurvatum
(n =14)
Jump
(n = 7)
Heel strike
Opposite toe off
Opposite HS
Toe off
Heel strike
Maximum hip generation
Maximum hip absorption
0.57
0.44
−0.07
0.26
0.23
1.01
−0.36
0.22
0.59
−0.14
0.16
0.05
0.98
−0.39
0.67
1.01
−0.07
0.21
0.29
1.50
−0.48
0.01
0.24
−0.39
0.10
0.32
1.48
−1.09
(0.67)
(0.38)
(0.33)
(0.20)
(0.68)
(0.65)
(0.33)
(0.39)
(0.30)
(0.30)
(0.21)
(0.07)
(0.61)
(0.24)
(1.32)
(1.16)
(0.21)
(0.26)
(0.26)
(1.10)
(0.45)
(0.87)
(0.61)
(0.50)
(0.33)
(0.25)
(0.57)
(0.48)
F valueb
Post-hocc
0.91
1.90
1.59
0.66
0.55
1.28
5.60*
M,C,R\J
a
Means and S.D. in parenthesis.
Statistic was done with one-way ANOVA.
c
Tukey’s post-hoc test was used to determine the significance between each pair of the four groups.
* PB0.01.
b
amplitude, which reached its peak in mid-stance, similar to a normal subject. There was no muscle activity in
the swing phase until terminal swing in all four groups.
3.5.2. Rectus femoris
Except the recurvatum group, the other three groups
had notable activity of rectus femoris immediately after
initial contact (Fig. 12). The crouch group had sustained greater firing in the stance phase, while the jump
group had the least activity. The mild group started the
firing activity from terminal stance, while the other
three groups had delayed onset of firing in mid-swing.
3.5.3. Biceps femoris
All the four groups had the firing activities of biceps
femoris in initial stance and terminal swing (Fig. 13).
The biceps femoris of the recurvatum group had less
activity than the other three groups in stance phase and
an earlier onset of firing in swing phase.
4. Discussion
problems in diplegic CP into jump, crouch, recurvatum
and stiff knee gait is widely accepted. Their description
was based on kinematics but our study has provided
kinetic information in a similar patient group. We
observed the same crouch, recurvatum and jump
groups but did not observe the stiff knee pattern described by Sutherland and Davids but did observe
another group where the kinetic patterns were not very
dissimilar from normals. There may be two explanations for this difference between the two studies. Firstly,
the populations studied may have differed and secondly
the additional information that we obtained from kinetics may account for this difference.
We found that the jump knee group had the largest
peak vertical force, necessitating extremely large push
up effect of the supporting leg. Excessive knee extensor
torque in the initial stance started from the extreme
flexion position. This might explain the eccentric contraction of hamstring with observed over-activity in
EMG. In initial stance, the sagittal ankle kinematics
revealed a slight increase in dorsiflexion, often without
heel strike, because of the increased knee flexion. How-
Sutherland and David’s classification [23] of knee
Fig. 10. Mean ankle joint power of four cerebral palsy groups.
Fig. 11. Mean linear envelopes of gastrocnemius of four cerebral
palsy groups.
230
C.-J. Lin et al. / Gait and Posture 11 (2000) 224–232
Table 4
Knee joint powersa at specific gait events and its peak values
Knee power, W/kg generation
(+)/absorption (−)
Mild
(n = 17)
Crouch
(n =8)
Recurvatum
(n =14)
Heel strike
Opposite toe off
Opposite HS
Toe off
Heel strike
Maximum generation
Maximum absorption
0.16
−0.02
−0.16
−0.12
0.09
0.60
−0.82
0.06
0.22
−0.63
−0.10
0.06
0.65
−1.13
−0.01
−0.32
0.10
−0.12
−0.05
0.64
−0.79
(0.38)
(0.29)
(0.37)
(0.22)
(0.11)
(0.28)
(0.37)
(0.32)
(0.40)
(0.70)
(0.23)
(0.12)
(0.20)
(0.54)
(0.62)
(0.48)
(0.49)
(0.21)
(0.20)
(0.33)
(0.43)
F valueb
Jump
(n =7)
0.20
1.24
−0.52
0.00
−0.04
1.88
−0.98
(0.43)
(1.05)
(0.37)
(0.15)
(0.23)
(0.91)
(0.33)
0.43
12.17*
4.40**
0.58
2.0
14.28*
1.25
Post-hocc
J\C,M,R
R\C
J\C,R,M
a
Means and S.D. in parenthesis.
Statistic was done with one-way ANOVA.
c
Tukey’s post-hoc test was used to determine the significance between each pair of the four groups.
* PB0.001;
** PB0.01.
b
ever, the plantar flexion moment increased rapidly and
might be considered to arise from triceps surae activity
as seen on the EMG. Ankle joint power revealed shock
absorption at this stage and we also observed on video
a mild toe strike and consider that the triceps surae was
contracting eccentrically at this stage. This was then
followed by a concentric contraction of triceps surae,
which created a period of excessive plantar flexion, and
generation of joint power in early second rocker. This
might explain why we observed a premature
plantarflexion during second rocker, which was not
mentioned in Sutherland and David report [23]. The
vertical force curve had a deep mid-stance trough created by concentric contraction of quadriceps femoris,
signifying the characteristic pattern of transmitting
body weight. In mid-stance, the knee moved back to
the normal extension position so the extensor torque
decreased rapidly, because it is no longer necessary.
Due to the mid-stance plantar flexion of ankle still
being resisted by a passive dorsiflexor moment, the
generation of ankle power decreased gradually. In late
second rocker, when the body weight was ahead of the
foot, premature plantar flexion of triceps surae occurred. The second peak of power generation preceded
the third rocker and might explain the appearance of a
double bump in the power pattern at the ankle. Whilst
the changes at the ankle and knee occurred mostly in
early and mid stance, the changes at the hip appeared
mainly in late stance. When the hip was extended and
the GRF passed behind the joint, the hip flexors contracted eccentrically producing power absorption and a
flexor moment. The hip extensors did not appear to
have a significant role in this pattern.
The crouch group showed a decreased and practically
absent mid-stance trough in the vertical force curve.
The decreased mid-stance trough reveals a poor efficiency of weight transmission pattern. When the knee is
held excessively flexed in stance and the GRF passes
behind the knee a net internal extension moment is
generated, which we observed in this group. In addition, there was a double-bump pattern in the knee
Fig. 12. Mean linear envelopes of rectus femoris of four cerebral
palsy groups.
Fig. 13. Mean linear envelopes of biceps femoris of four cerebral
palsy groups.
C.-J. Lin et al. / Gait and Posture 11 (2000) 224–232
231
Table 5
Ankle joint powersa at specific gait events and its peak values
Ankle power, W/kg generation (+)/generation (−)
Mild (n = 17)
Crouch (n =8)
Heel strike
Opposite toe off
Opposite HS
Toe off
Heel strike
Max generation
Max generation
0.25
−0.33
0.36
0.19
−0.00
1.21
−0.54
−0.20
−0.35
0.24
0.13
0.02
0.74
−0.79
(1.00)
(0.32)
(0.55)
(0.26)
(0.02)
(0.95)
(0.28)
(0.22)
(0.29)
(0.46)
(0.27)
(0.02)
(0.22)
(0.33)
Recurvatum
(n =14)
−0.26
−0.62
0.49
0.07
0.01
0.87
−0.78
(0.29)
(0.66)
(0.78)
(0.12)
(0.00)
(0.67)
(0.58)
Jump (n = 7)
−0.32
−0.32
0.11
0.01
0.02
0.89
−1.18
(0.38)
(1.03)
(0.32)
(0.07)
(0.02)
(0.19)
(0.71)
F valueb
1.86
0.72
0.60
1.42
2.95*
0.97
2.56
a
Means and S.D. in parenthesis.
Statistic was done with one-way ANOVA.
* PB0.05.
b
moment, similar to the findings of Ounpuu [7]. As the
ankle was held in extreme dorsiflexion position, the
GRF passes anteriorly producing an external dorsiflexor moment and an internal plantarflexor moment.
The loss of the mid-stance trough of the vertical ground
reaction force produces a flat moment pattern at the
ankle. Crouch gait produced increased power absorption at the knee in terminal stance as the quadriceps
contracted eccentrically in the presence of knee flexion.
Thus in crouch gait, energy transfers about the knee is
inefficient. We noted that the hip moment curve in the
crouch group had a relatively larger extensor torque
because of the hip flexion pattern in stance.
The knee moment in the recurvatum group was the
opposite to that seen in the crouch group and was
associated with an external extension moment and an
absorption power pattern that was not seen in the other
groups. The knee flexors were silent on EMG and the
internal flexor moment might originate from the passive
resistance of the posterior soft tissue structures of the
knee, instead of knee flexors themselves. It would be
clinically significant if this joint were at risk of damage
due to the absence of muscular support [6,7]. We also
noted a decreased period of second ankle rocker and
premature plantarflexion in this group. There was a
trend towards an increased ankle plantarflexor moment
that was also seen in the jump pattern group. However
the ankle moments did not show significant differences
between the four groups, though great variations in
kinematics were observed.
The knee moment patterns in the mild group were
very similar to those seen in normal children. The mild
group was the only one to show a net dorsiflexor
moment at the ankle at initial contact, implying that
the GRF was posterior to the ankle at this stage. The
mild group also had a normal first rocker and normal
ankle kinematics.
Our study has demonstrated kinetics in the three
knee patterns of jump, crouch and recurvatum gait seen
in diplegic CP. The jump group was characterised
excessive power generation, whilst this was lost in the
crouch and recurvatum groups. An understanding of
kinetics in this group may help in their clinical
management.
Acknowledgements
This work was supported by National Health Research Institute, DOH-HR-410 and DOH-HR-821, Taiwan, ROC.
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