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VOLUME 8, ISSUE 2 

 2025 
 

RESEARCH ARTICLE 

 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 

prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

 

  

 

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mailto:cpoj@online-publication.com
https://publicationethics.org/about/our-organisation
https://pmc.ncbi.nlm.nih.gov/journals/?term=%22Canadian+Prosthetics+%26+Orthotics+Journal%22
https://members.publicationethics.org/members/canadian-prosthetics-orthotics-journal
https://doi.org/10.33137/cpoj.v8i2.45790
https://pmc.ncbi.nlm.nih.gov/journals/?term=%22Canadian+Prosthetics+%26+Orthotics+Journal%22


 

1 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

 

 

RESEARCH ARTICLE 

 

EVIDENCE-BASED RECOMMENDATION OF A POWERED KNEE FOR TRANSFEMORAL 

BONE-ANCHORED PROSTHESES: A CROSS-SECTIONAL STUDY 

Frossard L1, 2, 3, 4 *, Laux S5, Geada M5, Tronicke L6, Fridriksson T6, Lechler K6  

1. YourResearchProject Pty Ltd, Brisbane, Australia. 
2. Griffith University, Southport, Australia.  
3. Queensland University of Technology, Brisbane, Australia.  
4. University of the Sunshine Coast, Sippy Downs, Australia. 
5. APC Prosthetics Pty Ltd, Alexandria, Australia.  
6. ÖSSUR, R&D, Medical Office, Reykjavik, Iceland.  
  
 

 

 

 

  

 

 

 

 

 

 

 

 

 

 

INTRODUCTION   

Clinical Outcomes of Bone-Anchored Prostheses 

A bone-anchored prosthesis (BAP) connected to an 

osseointegrated implant might be indicated for some 

individuals with transfemoral amputation (TFA).1-3 In 

principle,  daily  loading  regimen  applied  on  the   implant  

 

 

during prosthesis use may be related to at least six of the 

nine most common transfemoral bone-anchored prosthesis 

(TF-BAP) adverse events (e.g., superficial and deep 

infections, loosening, falls, periprosthetic fractures and 

implant breakage; Appendix-Figure S1).4,5 Ideally, the loads 

applied during rehabilitation and beyond should be within a 

pain-free and bespoke “Goldilocks zone” where the “right 

load” is applied at the “right time”.6-8 In all cases, it is critical 

to understand how the loading profiles vary between  

TF-BAP equipped with compatible components.9-12 

Understanding Prosthetic Loading Profile  

Approximately 65 publications referred to loading 

characteristics associated with lower limb BAPs, including 

* CORRESPONDING AUTHOR: 
Professor Laurent Frossard, (PhD) 

Affiliation: 1) YourResearchProject Pty Ltd, Brisbane, Australia; 2) Griffith 
University, Southport, Australia; 3) Queensland University of Technology, 
Brisbane, Australia; 4) University of the Sunshine Coast, Sippy Downs, 
Australia. 

E-Mail: laurentfrossard@outlook.com  

ORCID ID: https://orcid.org/0000-0002-0248-9589 

 

 
OPEN  ACCESS 

ABSTRACT 

BACKGROUND: A transfemoral bone-anchored prosthesis (TF-BAP) can be fitted with non-microprocessor-

controlled knees (N-MPKs), or with microprocessor-controlled knees, which can be passive (P-MPKs) or active 

(A-MPKs). The next generation of A-MPKs, including powered knees, is emerging. The understanding of the 

loading applied on TF-BAP fitted with these A-MPKs is limited. 

OBJECTIVE: This cross-sectional study aimed to characterize the load applied on instrumented TF-BAP fitted 

with an A-MPK (Power Knee, Össur, Iceland) during standardized daily activities. Furthermore, some load 

characteristics applied during walking were compared with TF-BAP fitted with N-MPK and P-MPK reported in 

the literature using similar approach. 

METHODOLOGY: Thirteen males fitted with a transfemoral press-fit osseointegrated implant participated in 

this study between 2021 and 2022. Forces and moments applied on the instrumented TF-BAP, fitted with a 

Power Knee (PKA01) and Pro-Flex (LP, XC) or Balance S feet (ÖSSUR, Iceland), were measured wirelessly 

using an iPecsLab (RTC Electronics, USA) during walking, ascending and descending ramp and stairs. We 

followed a 28-step process to characterize the loading pattern considering spatiotemporal gaits variables as 

well as loading boundaries and extrema.  

FINDINGS: Overall, 1,327 steps were analyzed. The cadence ranged between 34 ± 6 and 49 ± 13 strides/min. 

The maximum forces and moments recorded on the long, anteroposterior and mediolateral axes of the 

transducer were 1,258 N, 331 N and 234 N as well as 19 Nm, 74 Nm and 91 Nm, respectively. 

CONCLUSION: The Power Knee, combined with Pro-Flex or Balance S feet, may improve participants’ 

capacity to ambulate. Comparations with reference values indicated that transitions from N-MPKs or P-MPKs 

to the Power Knee are considered safe and likely to improve efficiency. This study contributed to evidence-

based recommendations of TF-BAP fitted with powered knees. Hopefully, this work will advance clinical 

practice guidelines for the growing population choosing bionic solutions.  

 

 

 

ARTICLE INFO 

Received: July 31, 2025 

Accepted: October 25, 2025 

Published: November 2, 2025 
 

CITATION 

Frossard L, Laux S, Geada M, 

Tronicke L, Fridriksson T, 

Lechler K. Evidence-based 

recommendation of a powered 

knee for transfemoral bone-

anchored prostheses: A cross-

sectional study. Canadian 

Prosthetics & Orthotics Journal. 

2025; Volume 8, Issue 2, No. 4. 

Https://doi.org/10.33137/cpoj.v

8i2.45790 

KEYWORDS 

Amputation; Artificial Limbs; 

Bionics; Kinetics; Loading;  

Bone-Anchored Prosthesis; 

Lower Limb; Prosthesis; 

Osseointegrated Implant; 

Microprocessor-Controlled 

Knees.  

Journal Homepage: https://jps.library.utoronto.ca/index.php/cpoj/index 

Volume 8, Issue 2, Article No. 4. 2025 

 

 

https://doi.org/10.33137/cpoj.v8i2.45790
mailto:laurentfrossard@outlook.com
https://orcid.org/0000-0002-0248-9589
https://doi.org/10.33137/cpoj.v8i2.45790
https://doi.org/10.33137/cpoj.v8i2.45790
https://jps.library.utoronto.ca/index.php/cpoj/index


 

2 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

landmark reviews presented by Niswander et al (2020) and 

Ravari et al (2024).13,14 These reviews indicated that 

portable kinetic systems including tri-axial transducers 

embedded into a lower limb BAPs have been used to 

measure directly the load profile applied on osseointegrated 

implants during standardized rehabilitation and daily 

activities.6,10,11,15-24  

Cross-sectional cohort studies have previously looked at 

instrumented TF-BAP fitted with components 

recommended as best-practice at the time, such as Total 

Knee 1900, C-Leg and Rheo Knee XC.6,15,16,22-24 In our 

previous study, 10 TFAs were fitted mainly with basic 

prosthetic knees components such as mechanically passive 

knees or non-microprocessor-controlled knee (N-MPKs), 

the first passive microprocessor-controlled knee (P-MPK) 

and various prosthetic feet component.15,16,25 More recently, 

in our study, 13 TFAs were fitted with the Rheo Knee XC 

(Össur) and energy-storing-and-returning feet (ESARs).6,26 

As presented in Frossard et al,25,26 the maximum force 

and moment expressed as a percentage of body weight 

(%BW) were 84 ± 7 %BW and 2.63 ± 1.04 %BW·m 

while walking with a TF-BAP fitted with the GaitMaster,  

Total Knee 1900, Adaptive, or C-Leg, and  

102 ± 7 %BW and 3.44 ± 0.98 %BW·m while walking with 

the Rheo Knee XC. Over time, the repetition of such studies 

has led to a more standardized ecological approach to 

characterize loading profiles. The strength of this ecological 

approach is to report everyday loading regimen but its 

limitation is to overlook informative 3D dynamic, kinematic 

and inverse dynamic data.17,21,27-32 

Need for Characterization of Loading Profile with the 

Power Knee 

Nowadays, the prescription of recent P-MPKs and ESARs 

components is commonly recognized as the cost-effective 

standard of care when fitting TF-BAP.1,6,13,14,33-37 The next 

generation of active microprocessor-controlled knees  

(A-MPKs), including powered knees, is emerging.38-40  

A-MPKs use motors to actively assist with activities such as 

walking, standing up and climbing stairs. The development 

of active prostheses is the subject of many research 

projects with the vision of making walking with a prosthesis 

more natural and efficient for the user through adaptive 

actuators.39-42 The Power Knee (Össur, Iceland) is the first 

commercially available motor-powered A-MPK. It actively 

supports flexion and extension adapted to the user´s 

activity.43 Furthermore, it can improve the loading symmetry 

between sound and prosthetic sides during walking and sit-

to-stand movements and supports the user during step-

over-step stair ascent.44 

To the best of our knowledge, there are limited studies on 

the loading profile associated with TF-BAP fitted with the 

Power Knee.36 Therefore, there is a need for studies 

characterizing the loading profile using an ecological 

approach to facilitate comparisons with previous studies 

that focused on other recommended components for  

TF-BAP.  

Purposes 

The purpose of this cross-sectional study was to 

characterize the loading profile applied on TF-BAP when 

fitted with the Power Knee using an ecological approach 

(e.g., direct measurement of the load in quasi real-world 

conditions). The specific objectives were to: 

1. Present the range and variability of spatiotemporal gait 

variables, the magnitude of loading boundaries, as well as 

the onset and magnitude of extrema applied to the 

instrumented TF-BAP fitted with a Power Knee, Pro-Flex 

(LP or XC), or Balance S feet during standardized straight-

level walking and while ascending and descending ramps 

and stairs,  

2. Compare some of these loading characteristics with 

those reported in the literature for TF-BAPs fitted with N-

MPKs and a recent P-MPK (Rheo Knee XC).6,15,16,20,25,26 

METHODOLOGY 

Design 

This cross-sectional interventional study was a part of a 

registered clinical trial (ClinicalTrials.gov: 2021-YRP-LLA-

Load-01). 

Populations  

Individuals fitted with TF-BAP were recruited by a 

prosthetist using established selection criteria presented in 

Appendix-Table S1.6,15,16,20,26,45 There was no specific 

exclusion criteria related to gender, ethnicity, height or 

functional level. All participants were fitted with a non-FDA 

approved press-fit implant, (i.e., Osseointegration 

Prosthetic Limb, Permedica SPA, Italy). Assessment took 

place in Sydney, Australia between December 2021 and 

June 2022. Participants signed a written ethical consent 

form (Protocol No: Bellberry HREC-2021-YRP-LLA-Load-

01). 

Extraction 

Load profile was extracted following a standardized 28-step 

process outlined in Table 1 that emerged from previous 

studies.6,10,11,15,16,18,20,22,26 Key steps of the process are 

detailed below. 

Recording 

The loading was recorded during Step 1-18 (Table 1-A). The 

instrumented prostheses included iPecsLab’s transducer 

(RTC Electronics, USA) fitted between the connector and a 

Power Knee (n = 13, 100%) so that loading could be 

measured directly (Appendix-Figure S2). The participants 

were fitted with Pro-Flex LP (n = 7, 53%), Pro-Flex XC (n = 

4, 30%) or Balance S (n = 2, 15%) prosthetic feet and their 

https://doi.org/10.33137/cpoj.v8i2.45790


 

3 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

own footwear. We purposely chose the LP and XC models 

within the Pro-Flex ankles family which are commonly 

recommended for patients in Australia based on their ability 

to tolerate high impacts. 

Each force (F) and moment (M) were measured wirelessly 

at 200 Hz and expressed in the transducer’s coordinate 

system (Appendix-Figure S2). It was aligned so that its axes 

corresponded as closely as possible to the anatomical long 

(LG), anteroposterior (AP) and mediolateral (ML) axes of 

the implant (Appendix-Figure S3). A prosthetist performed a 

standard static alignment guided by principles outlined in 

the literature.46 In all instances, the co-linearity of the long 

axes of the implant and the transducer depended on the 

offset of the connector used to achieve the desired 

alignment (Appendix-Table S2, Figure S4, Figure S5). The 

prosthetist also performed a dynamic alignment and 

adjusted the knee settings that suited participants’ 

preferences and comfort.  

The loading was measured while participants performed 

successively up to five trials of straight level walking, 

ascending and descending ramp and stairs (Appendix-Table 

S3). 

Participants were used to walk with a P-MPK such as C-Leg 

or Genium (Ottobock, USA) or Rheo Knee XC (Össur, 

Iceland) or the Power Knee. Regardless, they were trained 

on how to use the Power Knee functions prior each activity 

(e.g., step-over-step technique to ascend and descend 

stairs). Approximately 30-60 minutes of acclimation with the 

prosthesis were initially deemed sufficient to achieve the 

required confidence and warrant safety based on 

literature.47 Participants were instructed to perform each 

activity at a self-selected pace and to use the handrail if 

needed.  

Processing 

The loading was processed during Step 19-23 (Table 1-B) 

using customized Matlab software program (The 

MathWorks Inc., USA)6,15,16,20,25,26 This program enabled 

the identification of gait events as well as time normalization 

over the percentage of a gait cycle (GC) or support phase 

(SUP) and normalization of loading datasets by percentage 

of bodyweight (%BW, %BWm).  

Analysis 

The loading was analyzed during Step 24-28 (Table 1-C), 

also using Matlab software program. The loading profile 

was characterized using spatiotemporal variables, loading 

boundaries, and up to 10 loading extrema depending on the 

activities. For this study, we purposely characterized the 

loading during critical phases of GC (Table 1-Step 28), 

including: 

• Weight acceptance using six extrema occurring during 

initial phasis of the GC where the bodyweight must be 

applied onto the knee smoothly for comfort and safely to 

action stance control features,   

• Propelling loading using four extrema occurring during 

the final phasis of the GC where the knee should assist 

shifting the center of mass slightly sideway and more 

importantly forward onto the sound limb.   

Statistics  

The mean and standard deviation of spatiotemporal 

variables, loading boundaries and extrema were calculated 

after collating all GCs recorded for each activity.  

The variability of the dataset was determined using the 

percentage of variation (PV), calculated as: 

 

𝑃𝑉 = |
𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝐷𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛

𝑀𝑒𝑎𝑛
×  100| 

 

To be consistent with the literature reporting inter- and intra-

subject variability of loading data, we considered a PV 

below 20% to indicate low variability and a PV above 20% 

to indicate high variability, respectively.6,15,16,20,22,25,26 

Comparisons 

Selected indicators of the loading profile were benchmarked 

against reference datasets extracted from the literature 

including able-bodied participants as well as TFAs fitted 

with socket prostheses, N-MPKs (n = 8) and P-MPKs  

(n = 13).6,15,16,20,25,26  

We only considered previous studies that used a similar 

protocol to reduce the confounding effects of the 

measurements (e.g., selection criteria, direct load 

measurement, loading characterization). 

Differences between discrete indicators including 

spatiotemporal gait variables as well as loading boundaries 

and extrema were determined so that a positive difference 

indicated that the Power Knee was algebraically larger than 

the reference datasets. The relative difference between 

indicators was also expressed as a percentage of the Power 

Knee:  

 

𝑅𝑒𝑙𝑎𝑡𝑖𝑣𝑒 𝐷𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 (%) =
𝑃𝑜𝑤𝑒𝑟 𝐾𝑛𝑒𝑒 𝐷𝑎𝑡𝑎 − 𝑅𝑒𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝐷𝑎𝑡𝑎

𝑃𝑜𝑤𝑒𝑟 𝐾𝑛𝑒𝑒 𝐷𝑎𝑡𝑎
×  100 

 

We considered that an absolute relative difference superior 

to 10% was above a minimal clinically important difference 

(MCID). This threshold might appear low compared to other 

studies considering an MCID of 20% when comparing 

prosthetic knee components.50 Conservatively, we believe 

that a lower MCID was justified in the particular case of 

individuals fitted with TF-BAP given that their proprioception 

is increased due to osseoperception provided by the 

implant.6,51   

https://doi.org/10.33137/cpoj.v8i2.45790


 

4 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

  

Table 1: Overview of the standard ecological approach relying on 28-step process to record, extract and analyze to load profile applied on bone-anchored 

prosthesis emerging from the literature. F: Force; M: moment; LG: Long axis; AP: Anteroposterior axis; ML: Mediolateral axis; 

GC: Gait cycle; %GC: Percentage of gait cycle; SUP: Support phase; %SUP: Percentage of support phase; %BW: Percentage of bodyweight; 

%BWm: Percentage of bodyweight per meter; FLG1: First point of interest of the force applied on the long axis; FAP1:  First point of interest of the force 

applied on the anteroposterior axis; FML1: First point of interest of the force applied on the mediolateral axis; MLG1: First point of interest of the moment 

applied around on the long axis; MAP1: First point of interest of the moment applied around the anteroposterior axis; MML1: First point of interest of the 

moment applied around the mediolateral axis; FAP2: Second point of interest of the force applied on the anteroposterior axis; MLG2: Second point of 

interest of the moment applied around on the long axis; MML2: Second point of interest of the moment applied around the mediolateral axis; MML3: Third 

point of interest of the moment applied around mediolateral axis. 

Step Description 

A-Recording 

A.1-Equipment 

A.1.1-Portable kinetic system (iPecsLab, RTC Electronics, USA) 

1 Setup sampling recording of forces and moments at 200 Hz  
2 Setup connection so that loading data are sent wirelessly to laptop nearby 

3 Ensure that the forces and moments were measured with an accuracy of ±0.01 N and ±0.001 Nm, respectively  

4 Fit transducer of the iPecsLab to the instrumented prosthesis 

5 
Align the coordinate system of the transducer that its vertical axis was co-axial with the long (LG) axis of the implant and the other axes 
corresponded to the anatomical anteroposterior (AP) and mediolateral (ML) directions of the implant 

6 
Denote forces acting on the three axes of the transducer as FLG, FAP and FML where compression, anterior and lateral forces were positive, 
respectively 

7 
Denote moments around the three axes of the transducer as MLG, MAP and MML where external, lateral and anterior moments were 
positive, respectively 

8 A prosthetist performed a standard static alignment of the prosthesis guided by principles outlined in the literature 

9 Perform dynamic alignment and resistance adjustment for knee and foot that suited participants’ preferences and comfort 
10 Consider that the medullar and percutaneous parts of the implant as well as the tube and/or adaptor were one rigid part 

11 
Measure the offset of the distal end of connector attached to the percutaneous part and the centre of the Power Knee in relation to the origin 
of coordinate system of iPecsLab’s transducer 

12 
Calibrate the transducer at the end of the recording session when the prosthesis was removed using post recording bench top measurements 
(i.e., zero-offset) 

A.1.2-Video recording 

13 
Setup basic video recording using digital camera of each trial of daily activities to facilitate the analyzes and interpretation of the loading data 
(e.g., digital notebook) 

A.2-Activities 

14 Measure characteristics of physical setup used to perform straight level walking as well as ascending and descending ramp and stairs 
15 Train participant on how to use the Power Knee functions prior each of the ascending and descending ramp and stairs activities  

16 Ask participants to perform up to five trials in each activity consecutively at a self-selected comfortable pace and to use the handrail, if needed 

17 
Advise participants to use the step-over-step (e.g., normal reciprocal stepping pattern) rather that step-by-step (e.g., placement of both feet on 
the same step before the next step) technique while ascending and descending stairs, when possible 

18 Acclimate and practice with instrumented prosthesis for 30-60 minutes prior each activity  

B-Processing 

19 Calibrate the raw forces and moments for each trial by considering the magnitude of the load recorded during calibration 

20 
Detect of relevant segment of loading data by discarding the first and the last two to three strides recorded for each trial so that the steps 
analyzed where at a steady pace, outside of gait initiation and termination, respectively 

21 
Determine of gait events using the plot of FLG to detect manually individual heel contacts and toe-offs events within the relevant segment for 
each trial  

22 
Normalize datasets by the time from 0 to 100 throughout the gait cycle (GC) or support phases (SUP) to facilitate averaging of trials as well as 
reporting of spatiotemporal characteristic and extrema in percentage of gait cycle (%GC) or support (%SUP), respectively 

23 Normalize forces and moments datasets by percentage of bodyweight (%BW, %BWm) 

C-Analysis 

24 

Extract three spatiotemporal variables including the cadence in strides per minute (stride/min) for a given trial (i.e., duration between two 
consecutive heel contacts of the prosthetic limb so that cadence of prosthetic limb did not always equate to the number of steps ascended or 
descended during stairs activities depending on step-over-step or step-by-step technique), duration of gait cycle in seconds (s), and duration 
of the support phases in percentage of gait cycle (%GC) 

25 
Extract 12 loading boundaries across all gait cycles per activity regardless of the onset including the minimum, maximum, and maximum of 
the absolute minimum and maximum magnitude of forces in N and %BW and moments in Nm and %BWm  

26 
Extract 36 overall loading boundaries across all activities including the minimum, maximum, and maximum of the absolute minimum and 
maximum magnitude of forces in N and %BW and moments in Nm and %BWm 

27 

Extract semi-automatically (e.g., searching the minimum or maximum magnitude of forces and moment within a pre-set time window) up to 10 
loading extrema (i.e., points of inflection of the loading pattern occurring consistently over successive steps for a given activity for all 
participants per activity including onset in %SUP (i.e., time of occurrence of extremum) and magnitude in N and %BW or Nm and %BWm (i.e., 
minimum or maximum magnitude of point on the curve of forces and moment within a pre-set time window)  

28 
Characterize weight acceptance and propelling loading considering six (i.e., FLG1, FAP1, FML1, MLG1, MAP1, MML1) and four (i.e., FAP2, 
MLG2, MML2, MML3) loading extrema occurring during the critical initial and final phases of the gait cycle, respectively 

 

https://doi.org/10.33137/cpoj.v8i2.45790


 

5 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

RESULTS 

A cohort of 13 males with TFAs participated in this study (64 

± 13 years; 1.79 ± 0.06 m; 93.7 ± 15.5 kg; 27.6 ± 4.2 kg/m2), 

as detailed in Table 2. Participation of only males was 

unintended and accidental. The surgical timeline was  

11 ± 9 years since amputation and 6 ± 3 years since 

implantation. The residuum length was 33.6 ± 4.9 cm or  

71 ± 10 % of sound thigh. 

A total of 1,327 GCs was analyzed including 538 for 

walking, 230 for ascending ramps, 265 for descending 

ramp, 137 for ascending stairs and 157 for descending 

stairs activities (Appendix-Table S4). Only 7 (54%) 

participants could perform stairs activities using “step-over-

step technique (e.g., two-stairs at the time) and “foot on the 

edge of the step” techniques. 

Spatiotemporal Gait Variables 

As detailed in Table 3-A, 10 (67%) spatiotemporal variables 

showed a low variability across all activities. However, high 

variability was noticeable for five (33%) variables including 

the cadence during walking and descending ramp as well 

as the duration of the GC during walking, descending a 

ramp and ascending stairs. 

The percutaneous part was 0.8 ± 1.7 cm, -0.1 ± 0.6 cm and 

9.6 ± 1.5 cm while the geometrical center of the Power Knee 

was 0.1 ±1.3 cm, -0.2 ± 0.9 cm and -8.4 ± 0.6 cm away from 

the center of the transducer on the AP, ML and LG axes, 

respectively (Appendix-Figure S3, Table S2, Figure S4, Figure 

S5). The mean and standard deviation of the loading pattern 

applied on the transducer over the support phase during 

walking, ascending and descending ramp and stairs are 

presented in Figure 1, Figure 2 and Figure 3, respectively. 

Loading Boundaries 

As presented in Table 3-B, 54 (90%) out of the 60 loading 

boundaries showed high variability. The variability was low 

for the average minimum load on MML during ascending 

stairs and the average maximum loads on FLG in all 

activities. The loading ranged between: 

• -305 N or -32 %BW and 1,258 N or 147 %BW on FLG,  

• -331 N or -47 %BW and 224 N or 25 %BW on FAP,  

• -47 N or -6 %BW and 234 N or 21 %BW on FML,  

• 17 Nm or -2.2 %BWm and 19 Nm or 2.0 %BWm on MLG,  

• -74 Nm or -6.6 %BWm and 20 Nm or 1.9 %BWm on MAP,  

• -82 Nm or -8.7 %BWm and 91 Nm or 9.7 %BWm on MML. 

The positive and negative values depended on the 

orientation of the transducer coordinate system, as 

presented in Table 1-Steps 6 and 7.  

Table 2: Overall and individual demographics, amputation, and prosthetic information of participants fitted with the instrumented prosthesis (i.e., Power 

Knee, Pro-Flex LP, Pro-Flex XC, Balance S). BMI: Body mass index; TR: Trauma; TU: Tumor; L: Left; R: Right; AMP: Amputation; TF-BAP: 

Transfemoral bone-anchored prosthesis; %SND: Percentage of sound thigh length. 

No. 

Demographics Amputation 

Length of 
residuum 

Prosthesis 

Age Height Mass1 BMI2 Cause  Side  
Time 
since 
AMP 

Time 
since 
TF-
BAP 

Foot Footwear 

(Yrs) (m) (kg) (kg/m2)   (L/R) (Yrs) (Yrs) (cm) (%SND) 

1 60 1.77 83 25 TR R 1.94 1.91 38 87 Pro-Flex LP Running shoes 

2 62 1.78 62 18 TU R 4.11 3.88 22 50 Pro-Flex LP Running shoes 

3 66 1.83 108 31 TR R 30.63 9.70 34 77 Pro-Flex LP Running shoes 

4 59 1.78 95 28 TR R 5.43 4.03 38 77 Pro-Flex LP Dressing shoes 

5 64 1.70 96 33 TR R 21.06 12.30 28 70 Pro-Flex LP Running shoes 

6 85 1.83 115 33 TR R 18.73 5.19 32 71 Pro-Flex LP Flat Shoes 

7 56 1.83 95 27 TR R 3.08 3.06 41 82 Pro-Flex LP Runners 

8 63 1.85 114 32 TR L 5.93 5.64 38 79 Pro-Flex XC City Shoes 

9 35 1.87 108 29 TR L 12.39 10.64 32 64 Pro-Flex XC Runners 

10 62 1.83 86 24 TR L 9.44 5.23 33 62 Pro-Flex XC Flat shoes 

11 81 1.67 73 25 TR R 7.02 3.89 35 70 Pro-Flex XC Runners 

12 59 1.86 97 27 TU L 20.15 9.31 34 64 Balance S Running shoe 

13 76 1.73 86 27 TR L 2.46 2.46 32 68 Balance S Trekking shoes 

Mean 64 1.79 93.6 27.6     10.95 5.94 33.6 71.0   

SD 13 0.06 15.5 4.2     9.00 3.39 4.9 9.8   
 

1 Body mass without prosthesis; 2 Calculated based on body mass without prosthesis. 

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6 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

  

 

 

Figure 1: Average and standard deviation (thin lines) of loading profile applied on instrumented prosthesis with the Power Knee during walking 
(13 participants, 538 gait cycles). %BW:  Percentage of the bodyweight; %SUP: Percentage of the support phase. 

 

https://doi.org/10.33137/cpoj.v8i2.45790


 

7 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

  

 

Figure 2: Average and standard deviation (thin lines) of loading profile applied on the instrumented prosthesis with the Power Knee during 
ascending (12 participants, 230 gait cycles) and descending (12 participants, 265 gait cycles) ramp. %BW: Percentage of the bodyweight; 
%SUP: Percentage of the support phase. 

 

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8 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

  

 

Figure 3: Average and standard deviation (thin lines) of loading profile applied on the instrumented prosthesis with the Power Knee during 
ascending (7 participants, 137 gait cycles) and descending (7 participants, 157 gait cycles) stairs. %BW:  Percentage of the bodyweight; %SUP: 
Percentage of the support phase. 

 

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9 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

 

Table 3: Mean and standard deviation as well as variability of spatiotemporal variables, loading boundaries and loading extrema applied on the 
instrumented prosthesis with the Power Knee. SD: Standard deviation; S: Second; %GC: Percentage of gait cycle; F: Force; M: Moment;  
LG: Long axis; AP: Anteroposterior axis; ML: Mediolateral axis; %BW: Percentage of the bodyweight; %SUP: Percentage of the support phase; 
H: High percentage of variation; L: Low percentage of variation; FLG1: First point of interest of the force applied on the long axis; FAP1: First 
point of interest of the force applied on the anteroposterior axis; FML1: First point of interest of the force applied on the mediolateral axis; MLG1: 
First point of interest of the moment applied around on the long axis; MAP1: First point of interest of the moment applied around the 
anteroposterior axis; MML1: First point of interest of the moment applied around the mediolateral axis; FAP2: Second point of interest of the 
force applied on the anteroposterior axis; MLG2: Second point of interest of the moment applied around on the long axis; MML2: Second point 
of interest of the moment applied around the mediolateral axis; MML3: Third point of interest of the moment applied around mediolateral axis. 

  Walking 
Ascending  

ramp 
Descending 

ramp 
Ascending  

stairs 
Descending 

stairs 

A-Spatiotemporal variables 

Cadence (Strides/min) 49 ± 13 H 46 ± 8 L 43 ± 10 H 34 ± 6 L 45 ± 6 L 

Gait cycle (s) 1.3 ± 0.3 H 1.3 ± 0.2 L 1.5 ± 0.4 H 1.9 ± 0.4 H 1.4 ± 0.2 L 

Support (%GC) 63 ± 5 L 63 ± 4 L 62 ± 7 L 58 ± 6 L 52 ± 6 L 

B-Loading boundaries 

Minimum 

FLG (%BW) -0.9 ± 2.0 H -0.5 ± 0.7 H -0.4 ± 0.9 H -4.4 ± 3.5 H -2.7 ± 6.8 H 

FAP (%BW) -10.1 ± 3.8 H -8.8 ± 3.4 H -14.8 ± 6.2 H -19.9 ± 6.4 H -28.2 ± 7.4 H 

FML (%BW) -1.1 ± 1.1 H -1.1 ± 1.4 H -0.7 ± 0.6 H -0.4 ± 0.6 H -1.1 ± 1.0 H 

MLG (%BWm) -0.53 ± 0.33 H -0.33 ± 0.26 H -0.61 ± 0.41 H -0.81 ± 0.28 H -0.95 ± 0.41 H 

MAP (%BWm) -3.61 ± 1.07 H -3.50 ± 1.04 H -3.07 ± 1.10 H -2.92 ± 0.61 H -2.34 ± 0.70 H 

MML (%BWm) -2.32 ± 0.70 H -2.14 ± 0.62 H -3.58 ± 1.89 H -3.20 ± 1.05 H -6.14 ± 1.06 L 

Maximum 

FLG (%BW) 102.4 ± 7.1 L 100.4 ± 4.1 L 99.6 ± 11.4 L 99.4 ± 5.4 L 84.1 ± 14.8 L 

FAP (%BW) 16.4 ± 4.9 H 16.4 ± 3.3 H 8.6 ± 5.7 H 6.8 ± 4.6 H 4.3 ± 1.7 H 

FML (%BW) 10.1 ± 3.7 H 9.7 ± 3.6 H 8.5 ± 2.9 H 8.8 ± 3.7 H 6.3 ± 2.9 H 

MLG (%BWm) 0.88 ± 0.44 H 0.97 ± 0.34 H 0.34 ± 0.32 H 0.81 ± 0.36 H 0.21 ± 0.16 H 

MAP (%BWm) 0.61 ± 0.42 H 0.64 ± 0.49 H 0.37 ± 0.23 H 0.66 ± 0.41 H 0.44 ± 0.25 H 

MML (%BWm) 3.41 ± 1.29 H 5.11 ± 1.17 H 1.70 ± 1.28 H 6.19 ± 1.90 H 0.63 ± 0.35 H 

C-Loading extrema 

Onset 

Weight acceptance 

FLG1 (%SUP) 41.8 ± 14.63 H 50.3 ± 15.8 H 38.5 ± 13.8 H 73.6 ± 17.6 H 21.8 ± 12.8 H 

FAP1 (%SUP) 16.9 ± 6.2 H 17.6 ± 6.2 H 40.5 ± 26.0 H 18.8 ± 9.9 H 56.2 ± 17.2 H 

FML1 (%SUP) 44.2 ± 12.8 H 44.0 ± 11.9 H 45.6 ± 13.4 H 67.7 ± 20.3 H 30.9 ± 14.4 H 

MLG1 (%SUP) 23.7 ± 11.3 H 15.7 ± 7.0 H 35.7 ± 21.4 H 19.1 ± 7.7 H 53.4 ± 17.1 H 

MAP1 (%SUP) 45.0 ± 14.0 H 45.0 ± 13.6 H 47.8 ± 14.7 H 65.2 ± 25.2 H 26.3 ± 12.9 H 

MML1 (%SUP) 13.6 ± 11.0 H 6.5 ± 5.8 H 35.0 ± 31.3 H 52.8 ± 23.3 H 67.6 ± 14.3 H 

Propelling loads 

FAP2 (%SUP) 79.2 ± 5.1 L 79.1 ± 5.0 L 88.8 ± 9.9 L 76.6 ± 25.6 H - - 

MLG2 (%SUP) 68.6 ± 11.0 L 61.8 ± 11.7 L 77.9 ± 21.8 H 69.8 ± 20.8 H - - 

MML2 (%SUP) 65.2 ± 9.2 L 62.3 ± 8.9 L 83.5 ± 8.7 L - - - - 

MML3 (%SUP) 91.8 ± 5.4 L 92.3 ± 4.9 L - - - - - - 

Magnitude 

Weight acceptance 

FLG1 (%BW) 102.4 ± 7.1 L 100.4 ± 4.0 L 99.6 ± 11.4 L 99.4 ± 5.4 L 84.1 ± 14.8 L 

FAP1 (%BW) -10.1 ± 3.8 H -8.8 ± 3.4 H -14.7 ± 6.1 H -19.9 ± 6.4 H -28.2 ± 7.4 H 

FML1 (%BW) 10.1 ± 3.7 H 9.7 ± 3.6 H 8.5 ± 2.9 H 8.8 ± 3.7 H 6.3 ± 2.9 H 

MLG1 (%BWm) -0.53 ± 0.34 H -0.31 ± 0.27 H -0.59 ± 0.42 H -0.81 ± 0.28 H -0.94 ± 0.41 H 

MAP1 (%BWm) -3.61 ± 1.07 H -3.50 ± 1.04 H -3.07 ± 1.10 H -2.92 ± 0.61 H -2.34 ± 0.70 H 

MML1 (%BWm) -0.85 ± 1.02 H -0.26 ± 0.43 H 1.70 ± 1.28 H 6.19 ± 1.90 H -6.14 ± 1.06 L 

Propelling loads 

FAP2 (%BW) 16.4 ± 4.9 H 16.4 ± 3.3 H 8.2 ± 6.2 H 6.6 ± 4.7 H - - 

MLG2 (%BWm) 0.88 ± 0.44 H 0.97 ± 0.34 H 0.30 ± 0.35 H 0.80 ± 0.38 H - - 

MML2 (%BWm) 3.32 ± 1.37 H 5.01 ± 1.31 H -3.48 ± 1.93 H - - - - 

MML3 (%BWm) -2.27 ± 0.64 H -2.14 ± 0.63 H - - - - - - 

 

 

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10 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

Loading Extrema 

As detailed in Table 3-C and Appendix-Figure S6-Figure S15, 

the loading profile applied during the daily activities was 

characterized by up to ten extrema for level walking and 

ascending ramp, nine for descending ramp, eight for 

ascending stairs and six for descending stairs including: 

• First point of interest of the force applied on the long axis 

(FLG1),  

• First point of interest of the force applied on the 

anteroposterior axis (FAP1),  

• Second point of interest of the force applied on the 

anteroposterior axis (FAP2),  

• First point of interest of the force applied on the 

mediolateral axis (FML1),  

• First point of interest of the moment applied around on the 

long axis (MLG1),  

• Second point of interest of the moment applied around on 

the long axis (MLG2),  

• First point of interest of the moment applied around the 

anteroposterior axis (MAP1),  

• First point of interest of the moment applied around the 

mediolateral axis (MML1),  

• Second point of interest of the moment applied around the 

mediolateral axis (MML2)  

• Third point of interest of the moment applied around the 

mediolateral axis (MML3)6,26  

Altogether, the onset and magnitude of the extrema showed 

a high variability for 33 (77%) and 37 (86%) out of 43 

extrema, respectively. The six extrema occurring during the 

weight acceptance phase had an onset and a magnitude 

with high variability, expected for the magnitude of FLG1 

during all activities and MML1 during descending stairs. The 

four extrema occurring during the propelling phase had an 

Table 4: Differences in gait and load characteristics produced with Power Knee compared to reference values produced with Total Knee and 
Rheo Knee XC during walking.6,15,16,25,26 

 N-MPK (a) 15,16,25 P-MPK (b) 6,26 

  (Unit) (%) (Unit) (%) 

A-Spatiotemporal variables  

Cadence (strides/min) 2.12 4 B 2.43 5 B 

Duration gait cycle (s) -0.02 -1 B -0.07 -5 B 

Duration support (%GC) 6.69 11 A -0.26 0 B 

B-Loading boundaries (c)  

FLG (%BW) 16.5 16 A 0.4 0 B 

FAP (%BW) 2.5 15 A -3.4 -21 A 

FML (%BW) -1.0 -10 B 3.1 31 A 

MLG (%BWm) 0.40 45 A 0.15 17 A 

MAP (%BWm) 0.70 19 A 0.17 5 B 

MML (%BWm) 0.89 26 A -0.72 -21 A 

C-Loading extrema  

Weight acceptance 

FLG1 (%BW) 16.5 16 A 0.4 0.4 B 

FAP1 (%BW) -1.5 15 A 1.3 -12 A 

FML1 (%BW) -1.0 -10 B 3.1 31 A 

MLG1 (%BWm) -0.11 22 A -0.10 18 A 

MAP1 (%BWm) -0.70 19 A -0.17 5 B 

MML1 (%BWm) 1.00 -117 A -0.10 12 A 

Propelling loads 

FAP2 (%BW) 2.5 15 A -3.4 -21 A 

MLG2 (%BWm) 0.40 46 A 0.15 17 A 

MML2 (%BWm) 1.87 57 A -0.78 -23 A 

MML3 (%BWm) 0.17 -7 B 0.20 -9 B 
 

(a) Including polycentric Total Knee 1900 = 6 fitted with TruStep = 3, C-Walk = 2 or unknown = 1 prosthetic feet components extracted from 
references 15, 16, and 25; (b) Including Rheo Knee XC = 13 fitted with Pro-Flex LP = 7 or Pro-Flex XC = 4 prosthetic foot components; (C) 
absolute maximum magnitude. 

 

 

 

 

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11 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

onset with low variability, expected for FAP2 during 

ascending stairs and MLG2 during descending ramp and 

ascending stairs, but a magnitude with high variability.   

Benchmark 

As presented in Table 4-A and Appendix-Table S5, the 

duration of the support phases was also 7 %GC, 11% longer 

above MCID compared to N-MPKs. The differences in all 

the other spatiotemporal gait variables between the Power 

Knee and participants fitted with socket prostheses, N-

MPKs and recent P-MPKs were below MCID. The self-

selected walking cadence with the Power Knee was 9 

strides/min slower than able-bodied participants and 5 

strides/min faster than sockets users. The duration of the 

support phases was also 0.19 s.    

As outlined in Table 4-B and Appendix-Table S5-B, the 

differences between forces and moments applied by the 

Power Knee and TF-BAP fitted with N-MPK during walking 

were ranged between -4 N or -1.00 %BW and 209 N or 

16.50 %BW as well as 4.16 Nm or 0.40 %BWm and 9.98 

Nm or 0.89 %BWm, respectively. The six differences 

between forces and moments applied were above MCID 

expected from FML. Four out of six differences between 

forces and moments applied on the Power Knee and TF-

BAP fitted with P-MPKs were also above MCID ranging 

between -13 N or -3.38 %BW and 61 N or 3.13 %BW as 

well as -5 Nm or -0.72 %BWm and 4 Nm or 0.17 %BWm, 

respectively.  

As detailed in Table 4-C and Appendix-Table S5-C, walking 

with the Power Knee reduced three extrema (i.e., FAP1, 

MLG1, MAP1) and increased two extrema (i.e., FLG1, 

MML1) during the weight acceptance while increasing three 

extrema (e.g., FAP2, MLG2, MML3) during propelling 

loading above MCID compared to N-PMK. The Power Knee 

increased all forces extrema and reduced all moments 

extrema during the weight acceptance while increasing and 

decreasing two extrema during propelling loading compared 

to P-MPK. 

DISCUSSION 

This cross-sectional study characterized the loads applied 

to an instrumented TF-BAP fitted with an A-MPK (Power 

Knee, Össur, Iceland) during standardized daily activities. 

Key Results 

This cross-sectional study showed that the load applied on 

TF-BAP fitted with a Power Knee was characterized by:  

• A self-selected cadence ranging from 34 ± 6 to 49 ± 13 

strides/min during walking, ascending and descending 

ramp and stairs. 

• Absolute loading boundaries equal to 147 %BW on FLG, 

47 %BW on FAP, 21 %BW on FML, 2.2 %BWm on MLG, 

6.6 %BWm on MAP and 9.7 %BWm on MML. 

• A low variability for 10 (67%) of spatiotemporal variables 

but high variability for 54 (90%) loading boundaries and 

magnitude of 37 (86%) loading extrema. 

Interpretation 

Similarly to previous studies, the outcomes showed a high 

variability typical of symptomatic populations like 

TFAs.6,15,16,25,26 Several factors of heterogeneity might 

contribute to high variability such as the diversity of 

prosthetic feet, alignment of the prosthesis and offset of the 

transducer as well as short acclimation as detailed below.  

Compared to reference values collated by Frossard et 

al,20,25,52 the instrumented TF-BAP fitted with the Power 

Knee may restore noticeably the spatiotemporal gait 

variables. Indeed, the cadence was 11% faster above MCID 

than participants fitted with socket, at least when ambulating 

at self-selected pace. The loading boundaries were found to 

be within a range considered appropriate for safe coupling 

between healthy bone and implant. 

The extrema occurring during the weight acceptance and 

propelling loading including FLG1 and FAP2 were 16.50 

%BW (16%) and 2.49 %BW (15%) higher and above MCID 

for the Power Knee compared to TF-BAP fitted with N-MPK, 

respectively. Further studies will be required to confirm that 

these increases might translate into more symmetrical 

loading with the sound limb.53-55 Altogether, these outcomes 

suggest that the Power Knee may contribute to improve the 

walking ability, particularly walking pace, compared to N-

MPK.  

The outcomes of the comparison with recent studies 

involving the Rheo Knee XC and Pro-Flex feet might be less 

certain. FLG1 was 0.42 %BW (0.41%) higher but below 

MCID with the Power Knee confirming its weight 

acceptance abilities. FAP2 was 3.38 %BW (21%) less and 

above MCID with the Power Knee suggesting a relatively 

lower capacity to generate propelling forces. However, 

differences might be due to a larger proportion of 

participants fitted with Pro-Flex XC (n=9, 70%) in the P-MPK 

study.15,16,25 The design of the Pro-Flex XC allows higher 

ankle push-off power and range of motion compared to the 

Pro-Flex LP.56-58 Further investigations are required to 

establish the impact of prosthetic feet varying in stiffness 

and range of movement on the loading profiles of TF-BAP 

(e.g., index of anthropomorphy).12,48,59 

Limitations 

The limitations constricting clinical interpretations inherent 

to the study design related to: the sample size; the 

presentation of the load datasets in relation to the 

transducer rather than the implant; the offset of the 

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12 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

transducer attached to the connector; the dynamic 

alignments without standardization and stiffness of the 

prosthetic feet; the lack of spatial (e.g., walking base, step 

and stride length), dynamics (e.g., ground and handrail 

reaction forces), kinematics (e.g., trunk bending, hip range 

of movement) and kinetics (e.g., ankle, knee, and hip joint 

moments and work) characteristics; and, the educated 

choices for the PV’s and MCID’s thresholds. 

A specific limitation was the short acclimation with the 

instrumented prosthesis. We anticipated that participants 

will acclimate rapidly to the instrumented prosthesis given 

their previous experience with P-MPKs or A-MPKs.47 

However, optimizing individual settings for each task might 

required more than one session with the prosthetist and a 

longer adaptation. So, limited adaptation time to the active 

support of the device especially during ramp and stair 

activities might have led to a more tentative and variable gait 

pattern and slower walking speeds (e.g., increase variability 

of extrema, decrease propelling loading, use of the 

handrail).  

Generalization 

The main barrier to generalizing these outcomes was the 

relatively small sample size (N = 13) and the male-

dominated cohort. COVID-19 pandemic impeded 

recruitment of participants and extensive testing (e.g., 

acclimation). However, our ecological approach allowed to 

capture a larger number of steps than typical studies relying 

on fixed-equipment.21,27-32,53,54,60-63 As mentioned above, 

several weeks of acclimation might decrease variability and 

increase the generalization of the outcomes. The 

generalization of the outcomes to other commercially 

available powered knees might be uncertain due to different 

specificities of their design.  

Future Studies 

This study can inform the design of subsequent 

observational studies with larger cohorts focusing on 

loading profile applied on TF-BAP with various component 

configurations (ESARs, P-MPKs, A-MPKs).55,64-67 

Practically, the range of loading characteristics presented 

here can facilitate the calculation of cohorts’ sample sizes 

(e.g., statistical power).  

The understanding of the benefits of TF-BAP fitted with 

powered knees can be extended by other studies focusing 

on: functional outcomes; 3D dynamic, kinematic, kinetic; 

metabolic characteristics; and participant’s experience 

(e.g., device weight and noise).17,21,27,67 Furthermore, there 

is a need to establish the cause-effect relationships 

between loading characteristics and confounders related to 

demographics, amputation history, prosthetic arrangement, 

walking ability as well as the strength and safety of bone-

implant coupling.61,68-74 Finally, new systematic reviews and 

meta-analyses relying on advanced statistical approaches 

are required to determine the loading variability associated 

with components currently recommended for TF-BAP as 

well as their efficacy and safety (e.g., walking pace, weight 

acceptance, propelling load).13,73 

CONCLUSION 

Benchmark loading data for a powered knee currently 

recommended for TF-BAP is provided for the first time. 

Altogether, the spatiotemporal gait characteristics and the 

propelling loads suggested that fitting the Power Knee 

alongside Pro-Flex (XC, LP) and Balance S prosthetic feet 

may restore distinctly the capacity of participants fitted a 

transfemoral osseointegrated implant to ambulate. 

Indicative comparisons with the literature suggested that the 

loading profile applied with this combination of components 

is more suitable than N-MPKs and stacked up against 

recent P-MPKs. Therefore, one can argue that a routine 

transition from N-MPKs or P-MPKs onto the Power Knee 

appears safe and potentially effective.   

As listed above, this is the third study applying this protocol 

to assess ecological TF-BAP prosthetic loading. This 

protocol can facilitate cross-comparison of loading 

characteristics between studies. However, further 

standardization requires a consensus around loading 

criteria likely to warrant efficacy and safety of TF-BAP 

components (e.g., weight acceptance, propelling loading). 

These efforts might also contribute to the design of ISO 

norms for osseointegrated implants and BAP-specific 

components. 

In the meantime, this study producing Level IV evidence, 

participated in evidence-based prescription of TF-BAP fitted 

with powered knees. Hopefully, this work will also contribute 

to the developments of standard of care for growing 

population of individuals using bionic limbs. 

ACKNOWLEDGEMENTS 

The authors wish to acknowledge Felix Starker and Valentina Betti 

from ÖSSUR, Iceland; Jason Adams from ÖSSUR, Americas; and 

Christopher Lavender and Nicholas Marchand from ÖSSUR, 

Canada, for their contributions to the development of this project, 

as well as Dan Milius and Miriam Grant from APC Prosthetics Pty 

Ltd for their valuable assistance in organizing the data collection. 
The authors also thank the participants of this study for their 

valuable contribution.  

DECLARATION OF CONFLICTING INTERESTS 

• Laurent Frossard received compensation for the study design, 

data collection and processing as well as writing of the 

manuscript.  

• Stefan Laux has no conflict of interest. 

• Marta Geada has no conflict of interest. 

• Lisa Tronicke is employed by ÖSSUR that provided the 

components. 

https://doi.org/10.33137/cpoj.v8i2.45790


 

13 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

• Thor Fridriksson is employed by ÖSSUR that provided the 

components. 

• Knut Lechler is employed by ÖSSUR that provided the 

components. 

 

AUTHORS’ CONTRIBUTION 

• Laurent Frossard: Conceptualization, Methodology, Software, 

Validation, Formal Analysis, Investigation, Resources, Data 

Curation, Writing - Original Draft, Writing - Review & Editing, 

Visualization, Supervision. 

• Stefan Laux: Conceptualization, Methodology, Validation, 

Investigation, Resources, Writing - Review & Editing, 

Supervision, Funding Acquisition. 

• Marta Geada: Conceptualization, Methodology, Validation, 

Investigation, Resources, Writing - Review & Editing, Funding 

acquisition. 

• Lisa Tronicke: Conceptualization, Methodology, Supervision, 

Project Administration, Funding Acquisition. 

• Thor Fridriksson: Conceptualization, Resources, Project 

Administration, Funding Acquisition. 

• Knut Lechler: Supervision, Project Administration, Funding 

Acquisition. 

 

SOURCES OF SUPPORT 

This study was solely funded by ÖSSUR, Iceland. ÖSSUR has had 

no influence upon the design, data collection, analysis, or 

interpretation of this research study and no involvement in the 

decision to publish these results. 

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CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

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Frossard et al., 2025 

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https://doi.org/10.1682/JRRD.2012.08.0135
https://doi.org/10.1177/02692155231183779
https://doi.org/10.1016/j.clinbiomech.2025.106476
https://doi.org/10.1016/j.gaitpost.2024.05.019
https://doi.org/10.1016/j.clinbiomech.2011.11.011
https://doi.org/10.33137/cpoj.v1i2.32003
https://doi.org/10.1016/j.gaitpost.2018.07.059
https://doi.org/10.1080/17483107.2019.1579000
https://doi.org/10.1093/milmed/usae149
https://doi.org/10.1016/j.clinbiomech.2013.11.023
https://doi.org/10.1016/j.clinbiomech.2020.01.017
https://doi.org/10.1016/j.clinbiomech.2023.105948
https://doi.org/10.1097/CORR.0000000000003344
https://doi.org/10.1097/JPO.0b013e31829c221f


 

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Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

microprocessor knees while walking on level ground and ramps. 

Clin Biomech (Bristol). 2015; 30(2): 175-81. 

https://doi.org/10.1016/j.clinbiomech.2014.12.003 

66.Morgenroth DC, Roland M, Pruziner AL, Czerniecki JM. 

Transfemoral amputee intact limb loading and compensatory gait 

mechanics during down slope ambulation and the effect of 

prosthetic knee mechanisms. Clin Biomech (Bristol). 2018; 55:65-

72. https://doi.org/10.1016/j.clinbiomech.2018.04.007 

67.Kaufman KR, Bernhardt KA, Symms K. Functional assessment 

and satisfaction of transfemoral amputees with low mobility 

(FASTK2): A clinical trial of microprocessor-controlled vs. non-

microprocessor-controlled knees. Clin Biomech (Bristol). 

2018;58:116-22. https://doi.org/10.1016/j.clinbiomech.2018.07.012 

68.Lee WC, Doocey JM, Branemark R, Adam CJ, Evans JH, 

Pearcy MJ, et al. FE stress analysis of the interface between the 

bone and an osseointegrated implant for amputees--implications to 

refine the rehabilitation program. Clin Biomech (Bristol). 2008; 

23(10):1243-50. https://doi.org/10.1016/j.clinbiomech.2008.06.012 

69.Helgason B, Palsson H, Runarsson TP, Frossard L, Viceconti 

M. Risk of failure during gait for direct skeletal attachment of a 

femoral prosthesis: a finite element study. Med Eng Phys. 2009; 

31(5):595-600. https://doi.org/10.1016/j.medengphy.2008.11.015 

70.Newcombe L, Dewar M, Blunn GW, Fromme P. Effect of 

amputation level on the stress transferred to the femur by an 

artificial limb directly attached to the bone. Med Eng Phys. 2013; 

35(12):1744-53. https://doi.org/10.1016/j.medengphy.2013.07.007 

71.Prochor P, Frossard L, Sajewicz E. Effect of the material's 

stiffness on stress-shielding in osseointegrated implants for bone-

anchored prostheses: A numerical analysis and initial benchmark 

data. Acta Bioeng Biomech. 2020; 22(2): 69-81. 

https://doi.org/10.37190//ABB-01543-2020-02 

72.Ahmed K, Thornton M, Taylor SJG. Mechanical load applied by 

Intraosseous Transcutaneous Amputation Prosthesis (ITAP) during 

walking on level and sloped treadmill: A case study. 

Med Eng Phys. 2024; 124: 104097. 

https://doi.org/10.1016/j.medengphy.2023.104097 

73.Galteri G, Cristofolini L. In vitro and in silico methods for the 

biomechanical assessment of osseointegrated transfemoral 

prostheses: A systematic review. Front Bioeng Biotechnol. 

2023;11:1237919. https://doi.org/10.3389/fbioe.2023.1237919 

74.Betti V, Galteri G, Zaffagnini S, Alesi D, Morellato K, Palanca M, 

et al. Advantages of customization of osseointegrated implants in 

transfemoral amputees: A comparative analysis of surgical 

planning. J Orthop Surg Res. 2024; 19(1): 520. 

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https://doi.org/10.1016/j.clinbiomech.2018.04.007
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https://doi.org/10.1016/j.clinbiomech.2008.06.012
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https://doi.org/10.1016/j.medengphy.2013.%2007.007
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https://doi.org/10.3389/fbioe.2023.1237919
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Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

APPENDIX 

The supplement provides information about the confounders (e.g., selection criteria, alignment of instrumented prostheses, position of the 

percutaneous part and prosthetic knee in relation to the transducer, setup, number of steps analyzed), the dispersion and magnitude of extrema 

for each activity as well as comparative values for demographics, spatiotemporal variables, loading boundaries and loading extrema extracted 

from the literature. 

Confounders 

Table S1: Selection criteria applied for the recruitment of participants with unilateral transfemoral bone-anchored prosthesis. 

A-Inclusion criteria 

1. To be willing to participate to this project of research 

2. To be willing to comply with protocol 

3. To be between 18-80 years of age  

4. To be fitted with osseointegrated fixation more than 6 months prior testing 

5. To be fully rehabilitated 

6. To be able to walk 200 meters independently with prosthesis 

7. To be able to be fitted with the nominated ÖSSUR components  

8. To be a previous or current user of microprocessor-controlled knee  

9. To have a clearance of at least 6-8 cm between connector attached to distal end of percutaneous part of the fixation and prosthetic 

knee joint to fit the transducer  

B-Exclusion criteria 

1. To not be able to give informed consent 

2. To have mental illness or intellectual impairment 

3. To have major uncorrected visual deficit 

4. To have history of epilepsy or recurrent dizziness 

5. To have bilateral amputation 

6. To have self-reported pain level greater than 4 out of 10 at study outset 

7. To have experienced a fall within the last 8 weeks before assessment 

8. To present signs of infection 2 weeks prior testing session  

9. To have injuries involving contralateral (intact) limb 

 

 

Table S2: Position of the distal end of connector attached to the percutaneous part and the geometrical centre of the Power Knee in relation 
to the origin of coordinate system of iPecsLab’s transducer (RTC Electronics, USA) on the antero-posterior (AP), medio-lateral (ML) and vertical 
(VT) axes. 
 
 

Participant 

Distal end of the percutaneous part Centre of the Power Knee 

AP ML VT AP ML VT 

(cm) (cm) (cm) (cm) (cm) (cm) 

1 0.63 -0.46 9.19 -0.67 -0.36 -8.20 

2 2.19 0.72 9.91 -1.85 -1.33 -9.93 

3 -0.22 0.00 9.08 -0.79 -0.59 -8.83 

4 0.77 -1.20 8.12 0.39 1.16 -8.14 

5 -0.61 0.01 8.86 -1.06 -0.85 -8.08 

6 3.80 -0.59 8.23 -0.51 0.15 -8.56 

7 0.63 -0.73 8.77 1.41 1.19 -8.60 

8 -1.29 0.22 9.92 2.66 -0.81 -7.70 

9 -2.02 0.72 8.69 -0.83 -1.13 -8.36 

10 -0.87 0.16 12.08 -0.43 -0.82 -8.74 

11 1.65 -0.44 8.59 1.29 0.54 -8.54 

12 2.67 0.09 9.79 1.72 0.69 -7.84 

13 2.52 0.16 13.41 0.33 -0.23 -7.79 

Mean 0.76 -0.10 9.59 0.13 -0.18 -8.41 

SD 1.74 0.56 1.54 1.31 0.85 0.58 

 

 

 

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Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

 

Table S3: Description of non-experimental facilities. 

Activities Power Knee 

  Straight level walking   

  Location Indoor 

  Length (m) 14 

  Ascending and descending ramp    

  Location Indoor 

  Length (m) 5.70 

  Incline (deg) 3.72 

  Handrail height (m) 0.93 

  Ascending and descending stairs    

  Location Indoor 

  Number of steps 10 

  Step height (cm) 17 

  Step depth (cm) 29.5 

  Step width (cm) 1,130 

  Handrail height (m) 1 

 

 

Table S4: Overview of number of participants (N) and gait cycles (GC) analyzed during the assessment with the instrumented prosthesis (i.e., 
Power Knee, Pro-Flex LP, Pro-Flex XC, Balance S). 

 

Activity Participation Number of gait cycles 

 (N, (%)) (GC) 

Level walking 13 (100%) 538 

Ascending ramp 12 (92%) 230 

Descending ramp 12 (92%) 265 

Ascending stairs 7 (54%) 137 

Descending stairs 7 (54%) 157 

Total 13 (100%) 1,327 

 

 

 

 

 

 

 

 

 

 

 

 

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Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

 

 

Figure S1: Overview of six load-related outcomes susceptible to have a cause-effect relationship between the usage of the bone-anchored 
prosthesis (e.g., onset, magnitude and duration of loading) and the nine most frequent adverse events. Adapted from reference 4, and 5.  

 

 

 

Figure S2: Example of instrumented transfemoral bone-anchored prostheses including position and orientation of tri-axial transducer 

coordinate system of the portable kinetic system (iPecsLab, RTC Electronics, USA) for Participant 1. O: Origin of the transducer coordinate 

system, LG: Long axis, AP: Antero-posterior axis, ML: Medio-lateral axis, R: Residuum, I: Percutaneous part of the implant, C: Connector, T: 

Transducer, K: prosthetic knee. 

 

 

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Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

 

 

 

 

 

 

 

 

 

 

 

 

Figure S3: Individual alignment of the instrumented bone-anchored prosthesis fitted with iPecsLab’s transducer (RTC Electronics, USA) 
instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex XC, Balance S) and footwear for the cohort of 13 participants.  

 

 

  

 

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Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure S3 (continued): Individual alignment of the instrumented bone-anchored prosthesis fitted with iPecsLab’s transducer (RTC Electronics, 
USA) instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex XC, Balance S) and footwear for the cohort of 13 participants.  

 

 

 

 

 

 

 

 

Front View Back View Side View Front View Back View Side View 

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Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

 

 

 

 

Figure S4: Position of the distal end of connector attached to the percutaneous part and the geometrical centre of the Power Knee in relation 

to the origin of coordinate system of iPecsLab’s transducer (RTC Electronics, USA) on the antero-posterior (AP), medio-lateral (ML) and vertical 

(VT) axes of the sagittal and frontal planes. 

 

 

 

  

 

 

 

 

 

 

 

 

 

 

 

 

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23 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

 

Front view Side view  Front view Side view  

Participant 1 Participant 2 

    
Participant 3 Participant 4 

    
Participant 5 Participant 6 

    
Participant 7 Participant 8 

    
Participant 9 Participant 10 

    
 

 

 

 Figure S5: Individual position of the distal end of connector attached to the percutaneous part and the geometrical centre of the Power 

Knee in relation to the origin of iPecsLab’s transducer (RTC Electronics, USA) on the antero-posterior (AP), medio-lateral (ML) and vertical 

(VT) axes of the front and side views in the image (ICS) and transducer (TCS) coordinate systems. 

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24 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

 

Participant 11 

 

Participant 12 

    
Participant 13   

  

  

 

Figure S5 (continued): Individual position of the distal end of connector attached to the percutaneous part and the geometrical centre of the 

Power Knee in relation to the origin of iPecsLab’s transducer (RTC Electronics, USA) on the antero-posterior (AP), medio-lateral (ML) and 

vertical (VT) axes of the front and side views in the image (ICS) and transducer (TCS) coordinate systems. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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25 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

 

Level walking 

Detection of local extrema 

 

Figure S6: Dispersion (cross) and average (circle) for first (red), second (bleu) and third (green) points of interest of forces and moments for 

cohort of participants (N=13) fitted instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex XC, Balance S) during walking (538 gait 

cycles).  

 

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26 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

 

Characteristics of local extrema 

 

Figure S7: Box plots showing low and high 95% confidence interval, mean and outliers of the magnitude of up to three local extrema (PT1, 

PT2, PT3) of forces and moments for cohort of participants (N=13) fitted instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex 

XC, Balance S) during walking (538 gait cycles). 

 

 

 

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27 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

 

Ascending ramp 

Detection of local extrema 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure S8: Dispersion (cross) and average (circle) for first (red), second (bleu) and third (green) points of interest of forces and moments for 

cohort of participants (N=12) fitted with instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex XC, Balance S) during ascending 

ramp (230 gait cycles). 

 

 

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28 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

Characteristics of local extrema.  

 

 

Figure S9: Box plots showing low and high 95% confidence interval, mean and outliers of the magnitude of up to three local extrema (PT1, 

PT2, PT3) of forces and moments for cohort of participants (N=12) fitted with instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex 

XC, Balance S) during ascending ramp (230 gait cycles). 

 

 

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29 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

Descending ramp 

Detection of local extrema 

 

 
 

 

 

Figure S10: Dispersion (cross) and average (circle) for first (red), second (bleu) and third (green) points of interest of forces and moments for 

cohort of participants (N=12) fitted with instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex XC, Balance S) during descending 

ramp (265 gait cycles). 

 

 

 

 

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30 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

Characteristics of local extrema 

 

 

 

 

Figure S11: Box plots showing low and high 95% confidence interval, mean and outliers of the magnitude of up to three local extrema (PT1, 

PT2, PT3) of forces and moments for cohort of participants (N=12) fitted with instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex 

XC, Balance S) during descending ramp (265 gait cycles). 

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Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

  

Ascending stairs 

Detection of local extrema 

 

 

 
Figure S12: Dispersion (cross) and average (circle) for first (red), second (bleu) and third (green) points of interest of forces and moments 

for cohort of participants (N=7) fitted with instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex XC, Balance S) during ascending 

stairs (137 gait cycles. 

 

 

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32 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

Characteristics of local extrema 

 

 

Figure S13: Box plots showing low and high 95% confidence interval, mean and outliers of the magnitude of up to three local extrema (PT1, 

PT2, PT3) of forces and moments for cohort of participants (N=7) fitted with instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex 

XC, Balance S) during ascending stairs (137 gait cycles).   

 

https://doi.org/10.33137/cpoj.v8i2.45790


 

33 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

Descending stairs 

Detection of local extrema 

 

 

 

Figure S14: Dispersion (cross) and average (circle) for first (red), second (bleu) and third (green) points of interest of forces and moments for 

cohort of participants (N=7) fitted with instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex XC, Balance S) during descending 

stairs (157 gait cycles).   

 

 

 

https://doi.org/10.33137/cpoj.v8i2.45790


 

34 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

Characteristics of local extrema 

 

 

 

 

Figure S15: Box plots showing low and high 95% confidence interval, mean and outliers of the magnitude of up to three local extrema (PT1, 

PT2, PT3) of forces and moments cohort of participants (N=7) fitted with instrumented prosthesis (i.e., Power Knee, Pro-Flex LP, Pro-Flex XC, 

Balance S) during descending stairs (157 gait cycles). 

 

https://doi.org/10.33137/cpoj.v8i2.45790


 

35 

Frossard L, Laux S, Geada M, Tronicke L, Fridriksson T, Lechler K. Evidence-based recommendation of a powered knee for transfemoral bone-anchored 
prostheses: A cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 2, No. 4. Https://doi.org/10.33137/cpoj.v8i2.45790 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X EVIDENCE-BASED APPROACH TO POWERED KNEE USE IN BONE-ANCHORED PROSTHESES 

Frossard et al., 2025 

Comparative values 

Table S5: Mean and standard deviation of gait and load characteristics produced with a non-microprocessor-controlled knee (N-MPK) Total 

Knee and passive microprocessor-controlled knee (P-MPK) Rheo Knee XC during walking and the active microprocessor-controlled knee (A-

MPK)  Power Knee. SD: Standard deviation, N: number of participants, BMI: body mass index, LoR: length of residuum, %SND: Percentage 

of sound thigh length, s: Second, %GC: Percentage of gait cycle, F: Force, M: Moment, LG: Long axis, AP: anteroposterior axis, ML: 

Mediolateral axis, %BW: Percentage of bodyweight. 

 N-MPK (a)15,16,25 P-MPK (b) 6, 26 Power Knee (c) 

 (Mean±SD) (Mean±SD) (Mean±SD) 

A-Population       
Demographics     

Participants (n) 6 13 13 

Male (n) 2 11 13 

Female (n) 4 2 0 
Age (Yrs) 51 ± 6 57±14 64 ± 13 

Height (m) 1.75 ± 0.20 1.78 ± 0.08 1.79 ± 0.06 

Mass (kg) 75.94 ± 16.94 86.31 ± 18.03 93.65 ± 15.54 

BMI (kg/m2) 23.38 ± 2.70 25.92 ± 4.73 27.63 ± 4.18 
Amputation    

Cause      

Trauma (n) 4 9 11 

Tumor (n) 1 2 2 
Infection (n) 0 2 0 

Other (n) 1 0 0 

Left (N) 2 5 5 

Right (N) 4 8 8 
Time since AMP (Yrs) 28 ± 17 17 ± 19 11 ± 9 

Time since BAP (Yrs) 5 ± 2 2 ± 2 6 ± 3 

LoR (cm) 20.36 ± 4.87 28.38 ± 5.69 33.62 ± 4.91 

LoR (%SND) 49 ± 8 63 ± 11 71 ± 10 
B-Spatio-temporal variables       

Cadence (strides/min) 47 ± 4 47 ± 6 49 ± 13 

Duration gait cycle (s) 1.29 ± 0.11 1.34 ± 0.22 1.27 ± 0.31 

Duration support (%GC) 56 ± 2 63 ± 4 63 ± 5 
C-Loading boundaries (d)       

FLG (%BW) 86 ± 6 102 ± 7 102 ± 7 

FAP (%BW) 14 ± 4 20 ± 7 16 ± 5 

FML (%BW) 11 ± 4 7 ± 3 10 ± 4 
MLG (%BWm) 0.48 ± 0.26 0.73 ± 0.33 0.88 ± 0.44 

MAP (%BWm) 2.91 ± 0.87 3.44 ± 0.98 3.61 ± 1.07 

MML (%BWm) 2.52 ± 0.93 4.13 ± 1.21 3.41 ± 1.29 
D-Loading extrema       

Weight acceptance    

FLG1 (%BW) 86 ± 6 102 ± 7 102 ± 7 

FAP1 (%BW) -9 ± 4 -11 ± 4 -10 ± 4 
FML1 (%BW) 11 ± 4 7 ± 3 10 ± 4 

MLG1 (%BWm) -0.41 ± 0.22 -0.43 ± 0.29 -0.53 ± 0.34 

MAP1 (%BWm) -2.91 ± 0.87 -3.44 ± 0.98 -3.61 ± 1.07 

MML1 (%BWm) -1.85 ± 0.42 -0.75 ± 0.68 -0.85 ± 1.03 
Propelling loads    

FAP2 (%BW) 14 ± 2 20 ± 7 16 ± 5 

MLG2 (%BWm) 0.48 ± 0.26 0.73 ± 0.33 0.88 ± 0.44 

MML2 (%BWm) 1.44 ± 1.05 4.10 ± 1.25 3.32 ± 1.37 
MML3 (%BWm) -2.43 ± 0.72 -2.47 ± 1.01 -2.27 ± 0.64 

(a) Including polycentric Total Knee 1900 = 6 fitted with TruStep = 3, C-Walk = 2 or unknown = 1 prosthetic foot components extracted from 
15,16,25 (b) Including Rheo Knee XC = 13 fitted with Pro-Flex LP = 7 or Pro-Flex XC = 4 prosthetic foot components; (c) including Power 
Knee = 13; Pro-Flex LP = 7, Pro-Flex XC = 4, or Balance S = 2 prosthetic foot components; (d) absolute maximum magnitude. 

 

 

 

https://doi.org/10.33137/cpoj.v8i2.45790

