Clinical Outcomes With Passive MPKs vs. Powered Prosthetic Knees

Clinical Outcomes With Passive MPKs vs. Powered Prosthetic Knees by K4-level Transfemoral Amputees

The goal of this proposed project is to gather community-based data from the K4-level Transfemoral Amputee (TFA) population to aid in evidence-based prescription of powered prosthetic knees (i.e., choosing the right device to maximize the benefit for each patient). The investigators envision that this Level 1 submission will transition into a larger follow-on Level 2 trial that will explore a larger spectrum of patient populations (K2-K4), as well as testing additional Power Knees currently in development that are expected to become commercialized in the near future. The investigators intend to use this Level 2 trial data to guide the implementation of effective prescriptions towards those that can benefit most from a given device and limit prescription to those who would not see benefit in order to ensure the most judicious use of Department of Defense (DoD) and Veteran's Affairs healthcare dollars. The findings will also be shared with the research community to help drive the design of future devices by identifying what features and functions are most beneficial to which patient populations when the devices are used outside of the laboratory. In summary, more community-based data on how powered prosthetic knees compare with MPKs is needed to allow for improved clinical decision making and clinical outcomes.

Study Overview

• Status: Completed
• Conditions: Lower Limb Amputation Above Knee (Injury); Amputation; Prosthesis User; Amputation; Traumatic, Leg, Lower; Limb; Absence, Congenital, Lower; Amputation; Traumatic, Leg: Thigh, Between Hip and Knee
• Intervention / Treatment: Device: Power Knee

Detailed Description

The goal of this proposed project is to gather community-based data from the K4-level Transfemoral Amputee (TFA) population to aid in evidence-based prescription of powered prosthetic knees (i.e., choosing the right device to maximize the benefit for each patient). The investigators envision that this Level 1 submission will transition into a larger follow-on Level 2 trial that will explore a larger spectrum of patient populations (K2-K4), as well as testing additional Power Knees currently in development that are expected to become commercialized in the near future. The investigators intend to use this Level 2 trial data to guide the implementation of effective prescriptions towards those that can benefit most from a given device and limit prescription to those who would not see benefit in order to ensure the most judicious use of Department of Defense (DoD) and Veteran's Affairs healthcare dollars. The findings will also be shared with the research community to help drive the design of future devices by identifying what features and functions are most beneficial to which patient populations when the devices are used outside of the laboratory. In summary, more community-based data on how powered prosthetic knees compare with MPKs is needed to allow for improved clinical decision making and clinical outcomes.

This study will focus on investigating the tradeoffs between the commercially available Ossur Power Knee and traditional MPKs to identify the prosthetic knee that is best suited for K4 users during different tasks. The investigators will assess measured, observed, and self-reported outcomes achieved through real-world use of the prosthetic knees.

The results of this study will (1) provide initial data to inform the evidence-based prescription and use of powered knee technologies for K4-level individuals with sound scientific data, (2) provide pilot data for a larger clinical trial to further inform the evidence-based prescription of powered knee technologies to other K-levels to maximize patient benefit while optimizing device cost and thereby influencing clinical practice and informing policy decisions, and (3) provide data that can be disseminated to other researchers to inform the design of future powered prosthetic knees by understanding the needs of users and identifying the features and functions that are most valuable to this patient population as well as the capabilities and limitations of current devices.

The primary outcome measures for each aim are outlined as follows:

• [Mobility Primary Outcome]: daily number of steps taken
• [Safety Primary Outcome]: Activities-Specific Balance Scale
• [Wellbeing Primary Outcome]: PEQ-Well-Being (PEQ-WB)

The exploratory data collected in the in-clinic and take-home portions of this study will include number of steps and number of self-reported falls, and a series of standard outcomes measures, such as: 6MWT, SAI, RAI, PROMIS-PF short form, PLUS-M, TUG, ABC, RPE, PROMIS-Fat, fall count, PROMIS-29, ODI, PEQ-WB, and PROMIS-APSRA short form.

The investigators plan to perform a pilot longitudinal randomized crossover study to compare the powered knee and passive microprocessor knees in individuals with unilateral transfemoral amputation. The two interventions, or conditions, to be tested are: (A) Ossur PK and (B) a standard MPK. For this study the investigators will recruit individuals who are currently MPK users; therefore, for the MPK condition, they will wear their usual prosthesis (e.g. Otto Bock C-leg, Össur Rheo, etc) as they represent the current standard of care. This will be recorded as a potential confounder in post-hoc analysis. Each participant will be provided with prosthetic knees for the powered knee condition.

The order these conditions are tested in will be randomized across subjects. Block randomization using a previously developed custom software based on random number generation will be used to equally distribute the subjects into the 2 possible intervention orders (AB or BA). For each condition, the subject will be trained on and acclimated to the device during the first month of the take-home period, and then will continue to wear it at home after training for a total of three months per condition. There may be seasonal effects due to the timing of when the various test conditions are administered, however, the investigators plan to offset these effects with condition randomization, multiple site testing, and staggered start times.

Testing will consist of test sessions, training sessions, at-home wear of the device, and functional and self-report assessment at the end of each intervention condition. If the subject's current foot is not compatible with the Power Knee, they will be provided with a commercially available prosthetic foot for the study. In this case, the subject will be given an initial acclimation period of 1 month on the new foot before starting interventional testing.

After receiving IRB and HRPO (US Army Human Research Protection Office) approval, subjects will be recruited and screened for eligibility. If they are eligible and decide to participate, they will be scheduled for their first site visit. They will either be consented over the phone before their first site visit or at the first site visit. If over the phone, study staff will use the telephone script to confirm eligibility and guide the subject through consent form details. Subjects will be provided the informed consent form to read through entirely before signing, and are encouraged to ask questions at any time.

Prior to each condition, each subject will be fit and aligned on the knee by a trained certified prosthetist. An activity monitor (such as the GeneActiv™) will be worn by the subject. As the investigators have done in prior studies, the investigators will use the activity monitor to track the number of steps the subjects take in each condition. Each subject will wear the same foot for all study periods for comparability between the two knee conditions.

The subject will wear the knee being tested at home for three months. During the first month of each condition, subjects will be given time to acclimate to the knee being tested. Before and after each condition, the subject will complete a battery of outcomes and self-report surveys. Subjects will participate in at least two, but up to eight, 1 hour training sessions per knee. At a minimum, each subject will receive one training session to learn how to properly use each device for a variety of daily activities and a second session to demonstrate retention of the learned skills. The subject will continue training until they show retention of the understanding and/or proficiency of the device functions or until they have received eight training sessions, whichever comes first. After 8 training sessions, they will have completed all of the available training and will therefore continue with the study at their current proficiency level. For the powered knee condition, the investigators will work with trained and experienced clinicians, consulting prosthetic knee manufacturers as needed, to develop the training protocol and determine proficiency. At the last training session, the subject will complete a subset of the outcomes and self-report measures in order to collect and compare data from before and after the subject gets trained on each knee condition.

After the training visits are completed, subjects will be asked to continue to wear the knee full time for the remainder of the three month take-home period. Through Hanger's current patient care system, the investigators will have the ability to push out a digital to the patient's phone asking them whether they have experienced a recent fall. If they respond positively that they had a fall, follow up questions can be asked to get more specific details about the fall. After three months of at-home wear, the subject will return for the second test visit. During that visit, functional tests and self-report surveys will be administered. At the completion of the second test visit (Period 1), the subject will then be fit and aligned on the prosthetic knee condition for Period 2. The training, at home wear, and in-clinic assessments will be repeated for the next knee condition.

• Study Type: Interventional
• Enrollment (Actual): 13
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Massachusetts
    • Holliston, Massachusetts, United States, 01746
      • Liberating Technologies, Inc.
  • Texas
    • Austin, Texas, United States, 78758
      • Hanger Clinic

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Are at least 18 years old
• Unilateral transfemoral prosthesis user (limb absence between the knee and hip)
• Current user of a microprocessor-controlled knee (MPK)
• Have adequate clearance between distal end and ground for necessary knee and foot components
• Medicare Functional Classification Level (K-Level): 4
• Socket-Comfort Score: 6 or above to ensure adequate socket fit
• PLUS-M T-score of 55 or above
• Six months or more experience on a prosthesis
• Body weight between 50kg and 116kg (110lbs - 256lbs)

Exclusion Criteria:

• Present injuries to residual limb or contralateral leg affecting functional ability
• Socket issues/changes in the last 6 weeks
• Users with bone-anchored implants

Subjects can be excluded at the discretion of the investigator for other unforeseen disqualifying criteria (such as specific cognitive issues, etc.). Subjects in this study will not be discriminated by sex/gender or race/ethnicity.

Using a knee that the subject is unfamiliar with may increase the risk of falling. Therefore, pregnant women should not participate in the study and will be screened by self-disclosure.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Power Knee; The subject will wear the Ossur PK in place of their usual MPK for 3 months, as well as in the lab to complete outcome measures.	Device: Power Knee; Newest version of the commercially-available Power Knee developed by Ossur.; Other Names: Ossur Power Knee; Ossur Power Knee III; PK; PK3
No Intervention: Control (MPK); The subject will wear their usual Microprocessor Knee (MPK) for 3 months, as well as in the lab to complete outcome measures.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Daily Step Count	Prior to each condition, each subject will be fit and aligned on the designated knee by a trained certified prosthetist. An activity monitor (such as the GeneActiv™) will be worn by the subject for each intervention period during the final month of the condition. Similar to prior studies, the investigators will use the activity monitor to track the number of steps the subjects take in each condition per day. The number of steps per day are averaged over the final month in each condition. A higher value indicates a better outcome.	1 Month
Activities-Specific Balance Confidence Scale (ABC) - Measuring Change From Baseline	Activities-specific balance confidence (ABC) scale is a structured questionnaire that measures an individual's confidence during ambulatory activities without falling or experiencing a sense of unsteadiness. It consists of 16 questions gauging the individual's confidence while doing activities, from 0 (no confidence) to 4 (complete confidence). Therefore, the total score ranges from 0 to 64, with a higher value indicating a better outcome. This survey will be given at the end of each study condition (2 conditions, 3 months per condition). This survey will be administered as a part of the master questionnaire. Analysis is reported in % of balance confidence, which is found by taking their average of all questions (sum up all questions and divide by total number of questions) and dividing that average by 4.	At the end of each 3 month condition
PEQ-Well Being (PEQ-WB) - Measuring Change From Baseline	The version of the PEQ which will be administered consists of 2 questions in 1 category (well being). For purposes of easier administration, the investigators have adopted the modified 10-point ordinal scale version of the PEQ-WB (scale 1-10, where 1 is the worst and 10 is the best relative to the questions being asked). This survey will be given at the end of each study condition (2 conditions, 3 months per condition). This survey will be administered as a part of the master questionnaire. The reported result is the average of the 2 questions in the PEQ-WB. The range of this reported result is 1-10, where a higher value indicates a better outcome.	At the end of each 3 month condition

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Six Minute Walk Test (6MWT) - Measuring change from baseline	The 6MWT is a sub-maximal exercise test used to assess walking endurance and aerobic capacity. Participants will walk a set circuit for a total of six minutes. The distance covered over a time of 6 minutes is used as the outcome by which to compare changes in performance capacity. This assessment may be performed at each site visit.	Throughout study completion, an average of 6 months
Stair Assessment Index (SAI)	The Stair Assessment Index (SAI) is an observational outcome measure designed to assess an individual's ability to ascend and descend stairs. The SAI is a 14-level ordinal scale that spans a functional continuum from choosing not to ascend or descend the stairs to a fully independent step-over-step stair gait. A SAI rating is independently assigned to the activities of stair ascent and stair descent. These ratings reflect the individual's degree of independence and quality of movement in stair gait. The 14 ratings of the SAI are based on several central characteristics of stair gait including the ability to perform the task, the need for assistance, the use of an assistive device, and the gait style chosen to perform the task. This assessment may be performed at each site visit.	Before and after each 3 month condition
Hill Assessment Index (HAI)	The Hill Assessment Index (HAI) is an observational outcome measure designed to assess an individual's ability to ascend and descend hills. The HAI is a 12-level ordinal scale that spans a functional continuum from choosing not to ascend or descend the specified incline or decline to a fully independent symmetric gait pattern. A HAI rating is independently assigned to the activities of hill ascent and descent. These ratings reflect the individual's degree of independence and the quality of movement. The 12 ratings of the HAI are based on several central characteristics of inclined gait, including the ability to perform the task, the need for assistance, the use of an assistive device, and the gait style chosen to perform the task. This assessment may be performed at each site visit.	Before and after each 3 month condition
Timed Up and Go Test (TUG)	The Timed Up and Go (TUG) may be used to measure physical mobility, assess fall risk, and predict prosthetic nonuse in patients with a lower-limb amputation who are using a prosthesis. In the timed up and go (TUG) test, subjects are asked to rise from a standard armchair, walk to a marker 3 m away, turn, walk back, and sit down again. The test is timed in seconds using a stopwatch. The test is a reliable and valid test for quantifying functional mobility that may also be useful in following clinical change over time. This assessment may be performed at each site visit.	Throughout study completion, an average of 6 months total.
Patient Reported Outcomes Measures Information System - Physical Function (PROMIS-PF)	The form being administered is PROMIS Physical Function short form 10b.PROMIS Physical Function (PROMIS PF) measures the outcome of patients or clients by assessing physical function through a grading scale of activities of daily living. PROMIS PF is used as an outcome in research on the effectiveness of interventions. The questions are answered on a scale from 1-5, with 1 being 'unable to do' and 5 being 'able to do without difficulty', pertaining to an activity. This survey will be administered as a part of the master questionnaire.	Before and after each 3 month condition
PLUS-M Version 3.0 - Measuring change from baseline	This version of the PLUS-M is a 12 item short form. Responses are scored from 1-5, with 1 being 'unable to do' and 5 being 'without any difficulty', pertaining to an activity. The scores will be added together to make the 'raw score', which can then be translated to T-score, Standard Error, and percentile. This survey will be given at the beginning and end of each study condition (2 conditions, 3 months per condition). Additionally, this survey will be given at the subject's last training session, which is dependent on the subject's scheduling availability and proficiency with each knee condition. The subject will have between 2-8 training sessions per condition until deemed proficient or the 8th session has been completed, whichever comes first. All training sessions are expected to be completed within the first month of each condition. This survey will be administered as a part of the master questionnaire.	Throughout study completion, an average of 6 months total.
Borg Rating of Perceived Exertion (RPE)	The Borg Rating of Perceived Exertion (RPE) is a way of measuring physical activity intensity level. Perceived exertion is how hard the participant feels like their body is working. The original scaling is from 6-20, corresponding to approximate heart rate (x10 beats per minute). The investigators will be using the adapted Borg CR10 scale, which scales from 0-10 (0=no exertion at all, 10=maximal exertion).	Before and after each 3 month condition
Physiological Cost Index (PCI)	The PCI uses heart rate to indicate the energy cost of walking. The 3 items needed to calculate this measure are resting heart rate, working heart rate, and walking speed. PCI = (Working HR - Resting HR) / Walking Speed. Heart rate and walking speed will be collected and calculated for the 6MWT.	Before and after each 3 month condition
Patient Reported Outcomes Measures Information System - Fatigue (PROMIS-FAT)	The form being administered is PROMIS Fatigue short form 8a. The PROMIS Fatigue item banks assess a range of self-reported symptoms, from mild subjective feelings of tiredness to an overwhelming, debilitating, and sustained sense of exhaustion that likely decreases one's ability to execute daily activities and function normally in family or social roles. Fatigue is divided into the experience of fatigue (frequency, duration, and intensity) and the impact of fatigue on physical, mental, and social activities. The fatigue short forms are universal rather than disease-specific. All assess fatigue over the past seven days. The questions are answered on a scale from 1-5, with 1 being "not at all" or "never", and 5 being "very much" or "always". This survey will be administered as a part of the master questionnaire.	Before and after each 3 month condition
Self reported falls	A digital fall questionnaire will be delivered at most weekly through a HIPAA secure system to the patient's phone. This questionnaire has been used in the past by Hanger. If the subject responds positively that they had a fall, follow up questions may be asked to get more specific details. The subject may be asked to provide additional notes periodically to document their problems, experiences, and feedback.	Before and after each 3 month condition
Patient Reported Outcomes Measures Information System - 29 (PROMIS-29)	The PROMIS-29 is a short form assessment containing four items from each of seven PROMIS domains (Depression, Anxiety, Physical Function, Pain Interference, Fatigue, Sleep Disturbance, and Ability to Participate in Social Roles and Activities) which are all scaled from 1-5, plus one pain intensity question (0-10 numeric rating scale). This survey will be administered as a part of the master questionnaire.	Before and after each 3 month condition
Oswestry Disability Index (ODI)	The Oswestry Disability Index is a tool that researchers and disability evaluators use to measure a patient's permanent functional disability. The patient is asked 10 questions, each with 6 possible answers. The answers are scored 0-5. The total score corresponds to disability level (no disability, mild disability, moderate disability, severe disability, completely disabled). This survey will be administered as a part of the master questionnaire.	Before and after each 3 month condition
Patient Reported Outcomes Measures Information System - Ability to Participate in Social Roles and Activities (PROMIS-APSRA)	The PROMIS-APSRA is a short form that assesses an individual's perceived ability to perform their usual social roles and activities. The form being administered is PROMIS-APSRA short form 8a. The questions are answered on a scale from 1-5, with 1 being "never", and 5 being "always". This survey will be administered as a part of the master questionnaire.	Before and after each 3 month condition

Collaborators and Investigators

• Sponsor: Liberating Technologies, Inc.
• Collaborators: Hanger Clinic: Prosthetics & Orthotics
• Investigators: Principal Investigator: Jennifer Johansson, MS, Liberating Technologies, Inc.

Study record dates

Study Major Dates

• Study Start (Actual): May 1, 2022
• Primary Completion (Actual): August 28, 2024
• Study Completion (Actual): August 28, 2024

Study Registration Dates

• First Submitted: December 9, 2021
• First Submitted That Met QC Criteria: February 23, 2022
• First Posted (Actual): March 4, 2022

Study Record Updates

• Last Update Posted (Actual): June 26, 2025
• Last Update Submitted That Met QC Criteria: June 9, 2025
• Last Verified: June 1, 2025

More Information

Terms related to this study

• Keywords: amputee; lower limb amputee; transfemoral amputee; prosthetic knee; power knee; microprocessor knee; MPK; Ossur; lower limb prosthesis user
• Additional Relevant MeSH Terms: Wounds and Injuries; Amputation, Traumatic
• Other Study ID Numbers: 20216190

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: Yes