Muscle power compensatory mechanisms in below-knee amputee gait.

Objective: This three-dimensional and bilateral gait study on five below-knee amputees was undertaken to demonstrate the following: (1) how hip muscle powers can compensate for the lack of ankle function on the amputated side; and (2) how these compensatory mechanisms can influence muscle power activities in the sound limb.

Design: Gait data were assessed by an eight-camera high-speed video system synchronized to two force plates. The three-dimensional mechanical muscle powers were calculated at the joints of the lower limbs. Significant differences between each limb were determined using the Student's t test for paired data with P < 0.05.

Results: In the absence of ankle plantar flexor power, hip extensors and flexors as well as hip external rotators became the major power generators, whereas hip abductors and adductors and knee extensors muscle powers became the main source of absorption. For the sound limb, increased hip extensor activity was observed, accompanied by less hip abduction-adduction activity.

Conclusions: Perturbations in below-knee amputee gait affected the hip muscle powers on the amputated side in all three planes, although the hip frontal plane balance was modified in the sound limb.