PROJECT SUMMARY Microprocessor-controlled ankles have been shown to substantially improve mobility and stability in individuals with lower limb amputation, but these devices are typically only available to higher mobility users due to a lack of scientific evidence to justify insurance reimbursement. As such, many of the individuals with lower limb amputation that have the greatest need for advanced technology are unable to attain it. This Phase I application describes a microprocessor-controlled ankle prosthesis for individuals with lower- limb amputation that adapts seamlessly to varying activities and terrain, including slope walking and standing, stair walking, and highly-uneven terrain walking. As a result of this adaptation, the device is expected, and has been shown in preliminary work, to improve safety and enhance stability and comfort across these terrains. The primary goal of this Phase I proposal is to conduct a preliminary assessment of the value of the proposed prosthesis on lower mobility individuals with lower limb amputation. Such evidence is critical to justify insurance reimbursement, and so it is a vital step in the process of bringing microprocessor technology to individuals at the K2 mobility level. In order to do so, the investigators propose the following aims: 1) adapt the proposed ankle to optimize performance for K2 individuals with lower limb amputation, and 2) perform a pilot study (n=5) to quantify the effectiveness of the proposed ankle as compared to a predicate non-MPC ankle in improving performance for K2 individuals with lower limb amputation.