The study will investigate the effect over time of the Power Knee (Össur) on performance during daily activities in people with a unilateral transfemoral amputation, will determine subjective feelings and gait kinematics over time during daily activities and will investigate the association between subjective feelings and objective outcomes of performing daily activities.

Participants will visit the lab 6 times over a period of 5 weeks. The study includes a familiarisation phase (3 measuring moments) followed by the experimental phase (3 measuring moments). During the measuring sessions, participants will perform four tasks with their current prosthesis and with the Power Knee (Össur). The order in which the devices will be tested, will be reversed on each measuring moment to control for possible order effects and fatigue.

The experimental protocol will entail an L-test and slope walking test that will each be performed 3 times, followed by a 6 minutes of hallway walking (6MWT), 10 min rest and a dual-task 6MWT.

The slope walking test assesses the participants' ability to ascend and descend a 6 m long ramp of 10% inclination as fast as possible. For safety reasons bilateral handrails are warranted. Participants start the test in an upright position in front of the ramp and are asked to ascend the ramp, turn around on the platform, descend the ramp and return to the starting position.

The L-test, requires higher physical activity of the user. During the L-test, participants are asked to rise from a chair, walk 7 meters, turn 90 degrees, walk 3 meters, turn 180 degrees and then return in the same way to the seated position. A total distance of 20 meter is covered.

The 6MWT will be performed on a hallway at a self-selected walking speed, which closely relates to the most efficient walking speed.

The dual-task 6MWT will be compiled out of conducting a 6MWT while performing a cognitive task, i.e. serial subtractions. Serial subtraction is mental arithmetic task that tests attention and working memory. Participants will be asked to continually subtract sevens from a random selected 3-digit number as long as the duration of the test.

Inclusion Criteria:

• Unilateral transfemoral (above knee) amputation
• Healthy subject
• Medicare Functional Classification Level: K3-4

Exclusion Criteria:

• Any neurological disease
• Upper limb or bilateral amputation
• Stump pain or bad fit of the socket