Participants enrolled will already have their own microprocessor controlled (MP) non-powered knee prostheses as per inclusion criteria. Examples: OttoBock's C-Leg, Ossur's Rheo, Freedom Plie, Endolite Orion,etc.

Lower extremity AROM will be measured using an electrogoniometer. This is a computerized device capable of measuring angles and giving an electronic output of the measurements. This device has been found to have high ratings of reliability and validity in the lower limb.

The 6 minute walk test is performed as an objective evaluation of functional exercise capacity. The test measures the distance that the patient can walk on a flat, hard surface, indoors, in a period of 6 minutes. The walk test is patient self-paced and assesses the level of functional capacity. Patients are allowed to stop and rest during the test, however, the timer does not stop. If the patient is unable to complete the time, the time stopped is noted and reason for stopping prematurely is recorded. This test will be administered while wearing a mask to measure oxygen consumption. COSMED K4B2 (K4B2 COSMED, Italy) is a portable gas analysis system that measures oxygen consumption (VO2) and Carbon-dioxide production (VCO2 ) in a breath by breath fashion.

The Hill Assessment Index is a 12 point ordinal scale used to assess different gait patterns during ascent or descent of slopes. It was developed to detect differences in function with different knee units for transfemoral prosthetics. Time and oxygen consumption will be measured during ramp ascent and descent. These activities will be performed while wearing a mask to measure oxygen consumption. This test takes under 5 minutes to complete.

The Stair Assessment Index is a 14 point ordinal scale originally used to assess functional abilities during ascent and descent of stairs. Time and oxygen consumption will be measured during stair ascent and descent. These activities will be performed while wearing a mask to measure oxygen consumption. These tests take under 5 minutes to complete.

Time needed to cross a standard cross walk. The cross walk blinking signal test will measure how long it takes a participant to cross a designated street. The street that is designated for the test is 2 lanes and has ramps from the sidewalk to the street. The distance measured will be from the end of the ramp or edge of the curb on either side of the street. This distance is 36 feet. The literature recommends the cross walk velocity needed to safely cross is 0.9-1.2 m/s.

The GAITRite® system automates measuring temporal and spatial gait parameters via an electronic walkway connected to a computer. The GAITRite® electronic walkway contains sensor pads encapsulated in a carpet to collect gait information. The system can be laid over any flat surface. The GAITRite® electronic walkway for the study shall be a minimum of 14 feet long. The GAITRite® data capture was chosen as measurement of the patient's overall gait quality. Patients will be asked to walk at a self-selected speed and fast speed across the GAITRite® electronic walkway.

The 5 Time Sit to Stand Test is a measure of functional lower limb strength during transitional movement. The individual sits in a standard height chair (43-45 cm) and is instructed to stand up and sit down 5 times as quickly as possible. The individual is not allowed to use upper extremities to push off and is instructed to cross arms over chest if able to do so. The test is scored by measuring the time it takes to complete the 5 stands. If the patient is unable to complete all 5 stands or requires assist greater than contact guard the test is scored as a fail.

Test of dynamic balance that clinically assesses the person's ability to step over objects forward, sideways and backwards. The test takes less than 5 minutes to administer and tests activity of daily living and motor skills.

The TWWT is used to determine the effects of cognitive attentional demands during walking by introducing a secondary thinking and talking task, while walking. Participants will perform the following tasks: timed walking up to 300 meters, performing a thinking and talking (numerical and/or vocabulary) task while sitting, and performing a thinking and talking task while walking (dual task) Participants voice will be recorded when performing all the thinking and talking tasks.

This test will evaluate the participants gait characteristics and performance while walking on various surfaces that participants could encounter during activities of daily living. Participants will be asked to walk on typical outdoor uneven surfaces outside the entrance to the Rehabilitation Institute of Chicago (RIC), such as pavement, grass, uneven surfaces and ramps. Participants may use assistive device during this test. A researcher will walk with the participant to ensure safety and assist as needed.

A tool used to predict the ambulatory potential of lower limb amputees, and measure function post-rehabilitation. It was developed to provide a more objective approach to rating amputees under the various K Classifications. The test can be performed with or without the prosthesis. The test involves activities of transfers, balance and walking. Score is out of 39 with each item scored in the range of 0-2

Is a brief screening tool to provide a quantitative assessment of cognitive impairment and to record cognitive changes over time. The MMSE consists of 11 simple questions or tasks grouped into 7 cognitive domains. A possible score of 30 is used to provide a picture of an individual's present cognitive performance based on direct observation of completion of test items/tasks.

The questionnaire was developed specifically to provide functional outcome measures in prosthetics that are more tuned to prosthesis-related changes in quality of life. It is a self-report questionnaire containing 54 questions organized into nine functional domain scales. Each of the scales may be used individually to measure only a specific domain of interest. The PEQ has been used in a wide variety of studies and is validated.

The OPUS is a self-report questionnaire which is designed to evaluate the outcome of orthotic and prosthetic services. Three of the five domains will be administered: lower limb functional measure, health-related quality of life and satisfaction with device. The domains of upper limb functional measure and satisfaction with service are not applicable in this study.

The WHOQOL-BREF is a self-report questionnaire that measures an individual's perceived quality of life. It contains four domains which cover physical health, psychological health, social relationships, and environment. Scores range from 0- 100 with 100 indicating a higher quality of life. The scores can be broken down by domain or taken as a whole. The WHOQOL-BREF is valid cross-culturally.

The NPRS is a measure of perceived pain intensity. It consists of asking a participant to assign a number to the pain experienced along a 0 (zero) to 10 (ten) scale, with 0 being "no pain" to 10 being "worst pain imaginable."

The Socket Comfort Scale quantifies the amputee's experience of pain and discomfort while wearing a prosthesis. It consists of asking the participant to assign a number to the pain/discomfort of participant along a 0 (zero) to 10 (ten) scale, with 0 represents the most uncomfortable socket fit you can imagine and 10 represents the most comfortable socket fit.

The PLUS-M™ is a self-report instrument for measuring mobility of adults with lower limb amputation. It has been rigorously developed using modern psychometric methodology and is intended for use in clinical practice and research. PLUS-M™ instruments are based on a set of 44 calibrated questions called an item bank. PLUS-M™ instruments measure prosthetic users' mobility (i.e., the ability to move intentionally and independently from one place to another). PLUS-M™ questions assess respondents' perceived ability to carry out actions that require use of both lower limbs, ranging from household ambulation to outdoor recreational activities. The described activities relate to two primary forms of movement, locomotion (i.e., movement in a continuous, repeatable pattern) and/or postural transitions (i.e., movement from one position to another or one type of activity to another).

The QUEST is an instrument designed to measure the level of satisfaction attributed to assistive technologies. It does so using 27 variables which are scored in terms of perceived importance and satisfaction.

This back pain scale is a self-reported measure that evaluates a patient's functional status related to back pain.

A 6-20 item scale that measures perceived exertion during an activity.