Amputees’ Sound Knees Take Higher Loads When Stepping

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Among people with unilateral transtibial amputations, decreased mechanical work done by the trailing limb when descending a single step could affect load development and increase injury risk on the leading limb. To study those effects, a research team assessed the trailing limb mechanics on the development of lead limb load.

Eight people with amputations and ten able-bodied controls walked 5m along the length of a raised platform, descended a 14cm high single step, and continued walking.

The participants with amputations led with their intact limb during descent. Kinematic and kinetic data were recorded using integrated motion capture and a force platform system. Lead limb loading was assessed through vertical ground reaction force, knee moments, and joint reaction forces. Sagittal-plane joint work was calculated for the ankle, knee, and hip in both limbs.

The results indicated that there were no differences in lead limb loading despite differences in trail limb mechanics evidenced by amputees performing 58 percent less total work by the trailing (prosthetic) limb to lower the center of mass and 111 percent less for propulsion. The amputees descended the step significantly slower and performed significantly greater lead limb ankle work.

After accounting for speed differences, the researchers found that initial loading at the knee was significantly higher in the lead limb of the participants with amputations versus controls. They concluded that increasing lead limb work and reducing forward velocity may be effective compensatory strategies to limit lead limb loading during a step descent, in response to reduced trailing limb work.

The study, "Lead limb loading during a single-step descent in persons with and without a transtibial amputation in the trailing limb," was published in Clinical Biomechanics.