The purpose of this graduate student research study is to test that a specifically designed and novel robotic prosthetic leg (RPL) is feasible, safe and improves symmetry, efficiency, and metabolic function during sit-to-stand and stand-to-sit transitions as compared to the subject's prescribed device, and as compared to no device at all.

Phase 2 case study

• Two subjects will be fitted with a heart rate monitor and with an adapted waist belt with mobile phone attached.
• RPL alignment will be verified.
• The subjects will use the RPL in parallel bars 10 times and take rests as needed in a chair.
• The subjects will perform the timed up and go test (TUGT), 10-meter walk test (10MWT), and the 6-minute walk test (6MWT).
• The subjects will be fitted with retro-reflective markers.
• The subjects will be fitted with a portable oxygen uptake analyzer.
• A 4D motion-capture camera system will be used while performing TUGT and five times sit to stand (5XSTS).
• The subjects will perform the above tests in their prescribed daily-wear prosthesis, and then in the RPL.
• The subjects will complete the activities-based balance confidence (ABC) scale test.
• The subjects will be asked a series of open-ended questions regarding the experience, while being audio recorded.

Phase 3 pilot study

• Twenty subjects will be randomized into three treatment arms (no prosthesis, prescribed prosthesis, RPL).
• The subject will be fitted with a heart rate monitor.
• The subject will be fitted with a portable oxygen uptake analyzer.
• The subject will be fitted with the RPL, and the alignment of the RPL will be confirmed before testing.
• The subject will be fitted with retro-reflective markers.
• A 4D motion-capture camera system and force-plate will be used while performing the 5XSTS test in the assigned randomized condition. The test will be performed three times in each condition.
• The subject will return two more times to complete the tests in the remaining randomized conditions, with a two-week washout period between sessions.
• The subject will be given the ABC scale test in the beginning and at the end of this study.
• The subject will complete the technology attitudes questionnaire (TAQ).
• In total, subject participation will last 1 hour per day, for three sessions, two weeks apart.

Phase 2

Inclusion Criteria:

• unilateral limb-loss.
• amputation or knee disarticulation/transfemoral amputation
• can walk with a variable cadence (Level K3) or play sports (Level K4)
• uses a prosthesis for walking daily
• can stand for 30 seconds on one limb
• can follow one-step commands.

Exclusion Criteria:

• Those who can not walk with a variable cadence (Level K1 and K2)
• compromised skin on the residual limb (stump)
• uncontrolled swelling
• missing more than one limb

Phase 3

Inclusion Criteria:

• unilateral knee disarticulation or transfemoral amputation.
• can walk at a single speed (Level K2), can walk with a variable cadence (Level K3) or play sports (Level K4)
• can follow one step commands.

Exclusion Criteria:

• Those who do not use prosthesis for walking (Level K1)
• compromised skin on the residual limb (stump)
• uncontrolled swelling
• missing more than one limb