Evaluation of an Energy-Harvesting Knee Prosthesis in Transfemoral Prosthesis Users
Phase: NA
Conditions: Transfemoral Amputation, Artificial Limbs
Sponsor: Orthocare Innovations, LLC

Energy-Harvesting Knee Prosthesis: 
Assist-Knee 
 
 
NCT04023045 
Protocol # 7826-01 
 
Revised: 06/26/2019 
Approved by IRB: 07/15/2019 
 
 
Grant PI: 
Sarah Chang, PhD 
 
Orthocare Innovations, LLC 
123 Second Avenue South, Suite 220 
Edmonds, WA 98020 USA 
 
 

 
i. 
Purpose of the study and background 
 
Geriatric individuals with transfemoral limb loss can find rising from a chair 
challenging due to a loss of knee and ankle musculature on the prosthetic side, 
and declining or marginal strength on the sound side. Transitioning from a sitting 
to a standing position is much more difficult for an individual with transfemoral 
limb loss than an individual with no limb loss. When rising from a chair, 
individuals with limb loss rely on their sound limb and upper limb strength to lift 
their body weight. Geriatric transfemoral prosthesis users could retain 
independence if a prosthetic knee was capable of assisting with sit-to-stand-to-sit 
transitions. Unfortunately, the current designs of non-powered prosthetic knees do 
not assist with the sit-to-stand-to-sit transition, a task that is fundamental for 
normal activities of daily living.  
 
The objective of the energy-harvesting knee prosthesis (that we call Assist-Knee) 
is to create a lightweight, low-cost prosthesis that stores the prosthesis user’s 
potential energy during the stand-to-sit (SIT) transition and appropriately returns 
that energy to assist with the sit-to-stand (STAND) transition. Assist-Knee 
combines a mechanical spring and damper with a safety interlock mechanism 
(Figure 1).  
 
 
 
 
 
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Figure 1: CAD model of the Assist-Knee device 
 
 
 
 
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Figure 2: Assist-Knee function during STAND transitions. { text redacted } 
 
 
 
 
 
 
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Figure 3: { text redacted }   
 
 
 
 
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The purpose of the human subject testing will be to (1) validate the concept of the 
Assist-Knee design and function by testing the ability of Assist-Knee to harvest 
energy and return a sufficient amount of energy during the stand-to-sit-to-stand 
transition in a way that is clinically relevant, and (2) collect pilot data using the 
Assist-Knee device that can be included in a larger grant submission to perform a 
clinical trial with a larger representative population. We will also evaluate 
whether prosthetic users are able to wear and use the Assist-Knee device when 
walking.  
 
 

ii. 
Criteria For Participant Selection 
 
 
Our enrollment target for this pilot study will be 3 participants who are 
transfemoral prosthetic users. Our sampling plan for subjects will include both 
adult women and men (e.g. 1 adult woman and 2 adult men, or 2 adult women and 
1 adult man). The target subject distribution represents the results of the United 
States Census 2010 for Seattle, Washington: Asian (8.6%), Black (4.1%), and 
Hispanic or Latino (12.4%). We will endeavor to recruit participants that match 
the local demographic distribution. However, researchers will consider persons of 
all racial and ethnic backgrounds as equal candidates for inclusion in this work. 
The work has the potential to benefit minorities and non-minorities equally.  
 
The inclusion/exclusion criteria for the participants with lower limb loss are the 
following: 
 
Inclusion Criteria 
 
• Unilateral transfemoral limb loss 
• Age 21 – 80 years 
• At least one year post-amputation and currently successfully using a 
prosthesis  
• Uses modular endoskeletal prosthetic components 
• Has bilateral normal range of motion 
• Ability to perform the following activities: 
o Walking ability or ability to take steps over 10 meters 
o Upright standing stability  
o Stand-to-sit stability (i.e. go from a standing position to a seated 
position independently) 
o Sit-to-stand stability (i.e. rise from a seated position independently) 
• Ability to communicate individual perceptions in the English language 
• Ability to provide informed consent 
 
Exclusion Criteria 
 
• Confounding injury or musculoskeletal problem 
• Pregnancy 
• Lower limb peripheral neuropathy 
• Symptomatic cardiovascular disease or chronic obstructive pulmonary disease 
• Not able to read and understand English 
• Use of assistive devices for sit-to-stand and stand-to-sit (e.g. canes, walkers) 
 
 
 

iii. 
Methods and Procedures  
 
Recruitment of participants with lower limb loss 
 
Recruitment will be by referral from collaborating prosthetists or Orthocare 
Innovations’ study prosthetist. The prosthetist will either mail the attached letter 
(Assist-Knee solicitation letter.doc) or use the attached script (Assist-Knee 
solicitation script.doc) with patients that appear to meet the inclusion/exclusion 
criteria. If interested in participating in the study, the prosthesis users may choose 
to call Orthocare Innovations or choose to have Orthocare Innovations call them. 
 
Once contact is made between the prosthesis user and Orthocare Innovations’ 
research personnel, the Orthocare Innovations phone script will be followed 
(Assist-Knee solicitation script.doc). The research will be thoroughly described 
with opportunities for asking questions. Those interested in participating and 
those who meet our criteria will schedule an appointment for consenting at the 
Orthocare Innovations Biomechanics Laboratory. At this time, we will ask if they 
would like the consent document mailed or emailed to them so that they will have 
ample time to review the document prior to their visit. If they answer yes, we will 
mail or email a cover letter (Assist-Knee solicitation letter.doc) with a copy of the 
prosthesis user’s consent document (Assist-Knee consent subject.doc).  
 
Experimental procedures  
 
Since each participant’s prosthesis is unique, the prosthesis users will act as their 
own controls. All participants will have at least one visit to the Orthocare 
Innovations Biomechanics Laboratory, with each visit expected to last a minimum 
of four hours. The participants will first complete a baseline data collection using 
their existing habitual prosthesis. The participant’s individual power harvesting 
performance, kinematic data, and kinetic data will be measured in the Orthocare 
Innovations Biomechanics Laboratory for baseline comparisons, using a motion 
capture system (Vicon, Centennial, CO and force plates (AMTI, Watertown, 
MA). The participants will be asked to perform a variety of common activity tasks 
that may include: sit-to-stand maneuvers, walking on level-ground; turns during 
walking on level ground; initiating gait from a standstill; and stand-to-sit 
maneuvers. The main focus of the data collection is during the sit-to-stand-to-sit 
maneuvers. The participants will also be asked to complete the Timed Up and Go 
(TUG) test, which requires the participant to stand up from a chair, walk 3 m, turn 
around, walk 3 m back to the chair, turn around, and sit down onto the chair. After 
baseline data have been collected, the prosthesis user will then wear Assist-Knee 
and complete the same data collection in the Biomechanics Laboratory. Subjects 
will be asked to complete the Prosthesis Evaluation Questionnaire (PEQ) and a 
custom survey after completing the data collection for each habitual or Assist-
Knee condition (Assist-Knee_ParticipantQuestionnaire.docx). Subjects will also 
be asked to complete a demographic survey (Assist-Knee_Demographics.doc).  
 

Participants will wear the Assist-Knee system (Figure 4), which is designed to fit 
in place of their existing knee prosthesis and ankle-foot prosthesis. {text 
redacted} 
 
 
 
 
 
{ figure redacted } 
 
 
 
 
 
 
Figure 4: Representation of participant using Assist-Knee 
 
An Orthocare Innovations study research prosthetist will fit each participant with 
the Assist-Knee device. The participant will be trained by the research prosthetist 
on how to use Assist-Knee with an acclimation period of at least 60 minutes, with 
rest periods as needed, or until the subject feels comfortable using the system 
independently for gait and sit-to-stand-to-sit transitions. We intend to provide 
ample training on the system before independent use and will provide an operator 
for the clinical study if necessary. We will then test the effect of Assist-Knee on 
various movements (sitting down, standing up, gait via TUG test) and collect 
kinetic, kinematic, and temporal-spatial data. The data will be collected using the 
Orthocare Innovations’ Biomechanics Laboratory motion capture system (Vicon, 
Centennial, CO), force plates (AMTI, Watertown, MA), and a commercially 
available sensor (Smart Pyramid with Compas, Orthocare Innovations, Edmonds, 
WA) attached to the Assist-Knee.  
 
To mimic current clinical practice, the Assist-Knee device will be aligned by the 
prosthetist in static alignment to an optimal state by consensus of the research 
prosthetist and participant. { text redacted } The subject will be given an 
acclimation period of at least 10 minutes, with rest periods as needed, or until the 
subject feels comfortable using the system with each new combination. When 
performing the activities during the entire experiment, the participant will wear a 
gait belt held by the clinician for safety. Kinematic and kinetic data will be 
recorded.  
 
For each combination, subjects will perform a variety of tasks that may include: 
sit-to-stand maneuvers, walking on level-ground; turns during walking on level 
ground (e.g. for the TUG test); initiating gait from a standstill; and stand-to-sit 
maneuvers. The participants will not be allowed to use an assistive device during 
the sit-to-stand and stand-to-sit transitions, but the participants will be allowed to 
use an assistive device during the walking portion of the TUG test. The data 

capture process is anticipated to take no more than three hours. An additional hour 
may be required to fit the prosthetic device and does not require active walking by 
the participant. Participants will be allowed to rest as needed. The collected data 
will be used to determine the effectiveness of the experimental device. 
 
After testing { text redacted }, the participants will be encouraged to provide 
feedback on their perception of the device verbally and through the custom survey 
as well as complete the relevant questions from the PEQ. 
 
The following table (Table 1) describes a representative order of events and the 
outcome measures collected. { text redacted }. At least five satisfactory trials of 
motion analysis data and at least three satisfactory trials of TUG test for each 
{text redacted } combination will be collected.  
 
 
Table 1: Representative Experimental Protocol 
Survey: Prosthesis Evaluation Questionnaire (PEQ) and custom survey 
Visit 
# 
Activities to take place 
Outcome Measures 
Collected 
Hour 
1 
Screening, consent process, collection of 
demographic and anthropometric information, 
and administer survey for baseline prosthesis  
Demographic and 
anthropometric information, 
baseline survey responses 
Install Europa+ sensor in baseline prosthesis 
Hours 
1-3 
 
Collect motion analysis data on a variety of 
tasks with baseline prosthesis, perform TUG 
test 
Kinematic and kinetic data, 
TUG test 
Training period with Assist-Knee  
{ text redacted } 
Collect motion analysis data on a variety of 
tasks with Assist-Knee prosthesis, perform 
TUG test, administer survey, open-ended 
discussion with prosthesis user 
Survey responses, 
kinematic and kinetic data, 
TUG test, Assist-Knee 
settings 
Acclimation period with Assist-Knee  
{ text redacted } 
Collect motion analysis data on a variety of 
tasks with Assist-Knee prosthesis, perform 
TUG test, administer custom survey, open-
ended discussion with prosthesis user 
Survey responses, 
kinematic and kinetic data, 
TUG test, Assist-Knee 
settings 
Acclimation period with Assist-Knee 
{ text redacted } 
Collect motion analysis data on a variety of 
tasks with Assist-Knee prosthesis, perform 
TUG test, administer custom survey, open-
ended discussion with prosthesis user 
Survey responses, 
kinematic and kinetic data, 
TUG test, Assist-Knee 
settings 
Acclimation period with Assist-Knee  

{ text redacted } 
Collect motion analysis data on a variety of 
tasks with Assist-Knee prosthesis, perform 
TUG test, administer survey, open-ended 
discussion with prosthesis user 
Survey responses, 
kinematic and kinetic data, 
TUG test, Assist-Knee 
settings 
Return to baseline prosthesis 
 
 
iv. 
Data Analysis and Data Monitoring  
 
Data collected for the subjects with limb loss will be: contact information, age, 
sex, race, ethnicity, anthropometric measurements (height, distance from distal 
end of socket to knee center and knee center to ground), body mass, description of 
current prosthesis, time since limb loss, and cause of limb loss (scientifically 
relevant). The outcome measures collected from the subject experiment include 
kinematic, kinetic, and temporal-spatial parameters of gait; various data from the 
sensor installed on the Assist-Knee device; a record of verbal feedback regarding 
perceptions of the device; and written feedback with the Prosthesis Evaluation 
Questionnaire (PEQ) and custom survey. 
 
All subjects will be assigned a de-identified number that can be used to refer to 
subjects outside the research group, in order to protect confidentiality of the 
participant. Investigators solely participating in the human subjects experiments 
will only have access to subjects’ first names. The research coordinator, study 
prosthetist, and principal investigator will have access to first and last name, 
telephone number, email address, and mailing address. The research coordinator 
will use the mailing address (or email address) for mailing (or emailing) the 
consent prior to the first visit so the subject can review it at his/her leisure prior to 
the official consenting visit. All personal identifying information will be coded, 
keyed, and kept in locked file cabinets and/or on a password-protected computer. 
 
 
v. 
Risk/Benefit Assessment  
 
The risk to the participants will be minimal. The potential health risks to the 
participant with transfemoral limb loss are similar to those during routine 
prosthesis fittings. The difference is that the testing may go longer than the usual 
clinical visit. Therefore, fatigue from walking and performing the sit-to-stand-to-
sit transitions more than usual is a risk. Subjects will be told that they can sit and 
rest at any time. There are no foreseen psychological, social, or legal risks for 
participants. 
 
There is always a risk of privacy and confidentiality being breached. The privacy 
and confidentiality of subjects will be preserved using standard procedures for 
research data collection and storage. Uniquely identifying information will be 
coded and keyed. The key will be kept on a single password-protected computer 

and destroyed at the termination of the study. Unique identifiers will not be 
included in study data files other than the coding key and the consent forms. All 
data will be maintained on secure password-protected computers and locked file 
cabinets. HIPAA regulations will be observed for any personal, identifiable health 
information collected from the subjects.  
 
There are no direct medical benefits for participating in this study and, therefore, 
no alternative therapies or courses of action should the subject elect not to 
participate in this study. The primary benefit from participation is the 
advancement of prosthesis technology through the evaluation of our novel Assist-
Knee device.  
 
 
vi. 
Subject Identification, Recruitment, And Consent  
 
Recruitment of individuals with limb loss will be by referral from collaborating 
prosthetists or Orthocare Innovations’ study prosthetists. The prosthetist will 
either mail the attached letter (Assist-Knee solicitation letter.doc) or use the 
attached script (Assist-Knee solicitation script.doc) with prosthesis users that 
appear to meet the inclusion/exclusion criteria. If interested in participating in the 
study, the prosthesis users may choose to call Orthocare Innovations or choose to 
have Orthocare Innovations call them. 
 
Once contact is made between the prosthesis user and Orthocare Innovations 
research personnel, the Orthocare Innovations phone script will be followed 
(Assist-Knee solicitation script.doc). The research will be thoroughly described 
with opportunities to ask questions. Those interested in participating and those 
who meet our criteria will schedule an appointment for consenting at Orthocare 
Innovation’s Biomechanics Laboratory. At this time, we will ask if they would 
like the consent document mailed or emailed to them so that they will have ample 
time to review the document prior to their visit. If they answer yes, we will mail 
or email a cover letter (Assist-Knee solicitation letter.doc) with a copy of the 
patient’s consent document (Assist-Knee consent subject.doc).  
 
Aside from the participant’s time and transportation, there will be no cost to the 
participant. To compensate the participant’s time and transportation costs, the 
prosthesis user subjects will be paid { text redacted } at the end of the study or at 
the time of withdrawal.