Comparative Outcomes Assessment of the C-Leg With a New Knee Prosthesis

Inclusion criteria: * Unilateral transfemoral or knee-disarticulation amputee * 18 to 85 years of age * K3 (variable cadence and community) ambulators; * Current use of and experience with the C-Leg for at least 1 year * Ability to descend stairs and hills without caregiver and assistive devices * Be able to independently provide informed consent * Be willing to comply with study procedures. Exclusion criteria: * History of chronic skin breakdown on the residual limb * Conditions that would prevent participation and pose increased risk (e.g. unstable cardiovascular conditions that preclude physical activity such as walking) * Use of any assistive devices/walking aids, beyond a prosthesis, to ambulate * Unwillingness/inability to follow instructions