Segment angle. The child gait showed a smaller range of motion of the leg segment (68 degrees) than the adult gait (78 degrees), which was due to a greater amount of clockwise rotation in the adult gait. In the child gait peak clockwise rotation of the leg segment was 13 degrees at first left heel strike (0.00 seconds), while in the adult gait peak clockwise rotation was 24 degrees during the end of swing phase (1.19 seconds). The smaller clockwise rotation in the child gait could have been due to the smaller angle of peak knee extension in the child. Peak counterclockwise rotation was similar for the child gait (55 degrees) and the adult gait (54 degrees) and occurred at the beginning of swing phase in both the child (0.59 seconds) and the adult (0.83 seconds).
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Figure 3. Leg angle during child gait (left) and adult gait (right). The leg angle was calculated with respect to a vertical line passing through the knee joint. Zero degrees corresponds to the anatomical position. Increasing values on the graph represent clockwise rotation of the leg, while decreasing values represent counterclockwise rotation of the leg. | |
Joint angle 1. The knee flexed twice during the gait cycle of the child and the adult. There was a small amount of knee flexion after left heel strike during the stance phase and a larger amount during early swing phase. Despite the fact that the range of motion at the knee joint was quite similar in the child gait (64 deg) and the adult gait (63 deg), the actual position of the knee joint varied significantly between the child and the adult. The values for peak flexion and peak extension were smaller in the child than in the adult. Peak flexion in the child was 107 degrees and occurred during early swing phase (0.63 seconds), while peak flexion in the adult was 122 degrees and also occurred during early swing phase (0.89 seconds). Peak extension was 172 degrees in the child gait and occurred at the beginning of stance phase (0.00 seconds). Peak extension in the adult gait was 185 degrees, and occurred near the end of swing phase (1.19 seconds). The extension in the child gait during swing phase was considerably less than that of the adult, with peak extension occurring at the second left heel strike (161 deg), with a value of 128 degrees just prior to second left heel strike. Unlike the swing phase in the adult gait, where the knee extended and then flexed slightly before left heel strike, the swing phase in the child gait was characterized by continuous knee extension.
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Figure 4. Knee joint angle in child gait (left) and adult gait (right). The knee joint angle was calculated as the angle between the thigh and leg segments. Anatomical position occurs at 180 degrees. Increasing angles represent extension, and decreasing angles represent flexion. | |
Joint angle 2. The motion at the hip joint was very similar in the child and adult gait. Peak hip flexion in the child gait (201 degrees) was seen during midswing (0.69 seconds), while peak hip flexion in the adult gait (200 degrees) was seen later at the end of swing phase (1.22 seconds). The peak extension in the child (163 degrees) and the adult (161 degrees) was also very similar and occurred at the end of stance phase, at 0.46 seconds in the child and 0.73 seconds in the adult. Because of the similar peak joint angles, the range of motion in the child gait (38 degrees) and adult gait (39 degrees) was nearly the same.
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Figure 5. Hip joint angle in child gait (left) and adult gait (right). The hip joint angle was calculated as the angle between the trunk and thigh segments. Anatomical position occurs at 180 degrees. Increasing angles represent extension, and decreasing angles represent flexion. | |
Joint velocity. The knee joint angular velocity was analyzed for a complete gait cycle. The peak flexion velocity was greater in the child gait (459 deg/s) than in the adult gait (314 deg/s). This maximum flexion velocity occurred at the end of stance phase in both the child (0.53 seconds) and the adult (0.76 seconds). Peak extension velocity in the child gait (259 deg/s) was less than that in the adult gait (332 deg/s). In the child gait this maximal extension velocity occurred at the end of swing phase, while in the adult gait maximal extension velocity occurred during the middle of swing phase (1.09 seconds). The adult showed flexion at the end of the swing phase while the child did not.
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Figure 6. Knee angular velocity in child gait (left) and adult gait (right). Positive velocity represents extension while negative velocity represents flexion. | |
Angle-Angle Plot. The knee joint showed a greater range of motion than the hip joint in both the child and the adult in the gait cycle. The motion between the knee and hip joint was relatively decoupled in both the child and the adult, and the child's knee flexed less during the stance phase. At the beginning of the stance phase, the hip extended, while the knee flexed. This was followed by a period of knee extension, and continued hip extension. There was a decoupled coordination between the hip and knee joints as the knee joint switched from extension to flexion and the hip joint began to flex. There was closer coupling between the knee and hip joints in the child at this transition than in the adult. Following this transition, the hip and knee joint angles were coordinated in phase and changed at a constant ratio until the end of stance phase, with knee and hip flexion. At the start of the swing phase, the hip and knee joint angles continued to be coordinated in phase and were changing at a constant ratio. This was followed by a period of coupling between the hip and knee with hip flexion and knee extension. At the end of swing phase, the knee angle was increasing (extending) while the hip joint angle remained relatively constant.
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Figure 7. Coordination of knee joint and hip joint angles in child gait (left) and adult gait (right). Arrows indicate the direction of movement and the small boxes indicate the start positions. LTO stands for left toe-off and represents the end of stance phase. | |
