Gait research on trans-femoral prosthesis users has shown that the metabolic costs for these individuals are significantly higher than those of able-bodied individuals for level-ground walking. Additionally, trans-femoral amputees exhibit a much higher degree of gait asymmetry between the affected and non-affected sides, leading to reduced walking speeds and increased hip and back pain compared to non-amputees. This project consists of a clinical study of five to ten unilateral trans-femoral amputees using either a conventional or a powered knee prosthesis and height-weight matched able-bodied individuals. This work will compare the metabolic cost of transport and biomechanics of conventional standard of care prosthetic knees with a novel powered knee. It is hypothesized by using a powered prosthetic knee both the metabolic and biomechanical aspects of amputee gait can be improved.