Segment angle. The absolute angle of the trunk was analyzed for one complete gait cycle in both the able-bodied gait and the amputee gait. The amputee trunk showed a greater range of motion (10 deg) than that of the able-bodied trunk (6 deg). The amputee trunk had a minimum angle of 3 degrees (at the second heel strike) and a maximum angle of 13 degrees (during early swing phase). The able-bodied trunk had a minimum angle of -1 degrees (at foot flat) and a maximum angle of 5 degrees (during early swing phase).
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Figure 3. Trunk angle during the able-bodied gait (left) and the amputee gait (right). Trunk angle is calculated between the trunk segment and a vertical axis through the hip joint, where the upright position (anatomical) corresponds to zero degrees. Positive values represent clockwise rotation of the trunk and negative values represent counterclockwise rotation | |
Joint angle 1. Despite the fact that the range of motion at the ankle joint was quite similar in the able-bodied gait (26 deg) and the amputee gait (23 deg), the actual positions of the ankle joints were quite different. In the able-bodied gait, the ankle joint moved from 95 degrees (during midstance) to 121 degrees (during early swing phase). In the amputee gait, the ankle joint moved from 66 degrees (during early swing phase) to 89 degrees (just before toe off). The average ankle angle in the amputee gait was 77 degrees, 30 degrees smaller than that of the able-bodied gait.
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Figure 4. Ankle joint angles in the able-bodied gait (left) and the amputee gait (right). The ankle joint angles were calculated as the angle between the shank segment and the foot segment. The anatomical position of the ankle joint is approximately 110 degrees for able bodied gait and approximately 75 degrees for the amputee gait. In able bodied gait, an ankle angle less than 110 degrees represents dorsiflexion whereas an angle greater than 110 degrees represent plantarflexion. In amputee gait, an ankle angle less than 75 degrees represents dorsiflexion whereas an angle greater than 75 degrees represent plantarflexion. | |
Joint angle 2. The range of motion of the knee joint was greater in the amputee gait (75 deg) than in the able-bodied gait (64 deg). In both movements, peak flexion occurred in the middle of swing phase. In the able-bodied gait, peak extension occurred during the late part of swing phase, while in the amputee gait, it occurred at the second heel strike. The peak flexion in both the able-bodied and amputee gait was 107 degrees. In contrast, the peak extension differed in the able-bodied gait (171 deg) and the amputee gait (181 deg).
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Figure 5. Knee joint angles in the able-bodied gait (left) and the amputee gait (right). The joint angles are calculated between the thigh segment and the shank segment. Anatomical position corresponds to 180 degrees. Increasing angles represent extension whereas decreasing angles represent flexion. | |
Joint velocity. The angular velocity for knee joint was analyzed for one complete gait cycle in both movements. While the peak flexor angular velocity in the able-bodied gait was only 270 degrees per second, it was 429 degrees per second in the amputee gait. The peak extensor angular velocity was similar for both the able-bodied gait (324 degrees per second) and the amputee gait (357 degrees per second).
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Figure 6. Knee joint angular velocity in able-bodied gait (left) and the amputee gait (right). Positive velocity represents extension whereas negative velocity represents flexion. | |
Angle-Angle Plot. The coordination of the knee and ankle joints was quite similar. The majority of the motion occurred at the knee joints. When the ankles did move, they were coupled with knee movements. Increasing knee angles represented extension while decreasing knee angles represented flexion. In the able-bodied gait, ankle angles greater than 110 degrees represented plantarflexion while ankle angles less than 110 degrees represented dorsiflexion. In amputee gait, ankle angles less than 75 degrees represents dorsiflexion whereas ankle angles greater than 75 degrees represent plantarflexion. When the knee joint was at its greatest flexion, just after toe off, the able-bodied ankle plantarflexed. At that same position in the gait cycle, that amputee ankle remained dorsiflexed. Additionally, the amputee ankle exhibited greater plantarflexed from heel strike to foot flat.
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Figure 7. Coordination of ankle and knee joint angles in the able-bodied gait (left) and the amputee gait (right). The arrows indicate the direction of motion (with the tails placed close to the first frame of each movement). | |
