Powered vs Conventional Prosthetic Knees for Amputation

(OPKTFA Trial)

Overseen By Rebecca Stine, MS

Age: 18+

Sex: Any

Trial Phase: Academic

Sponsor: VA Office of Research and Development

Must not be taking: Balance medications

Disqualifiers: Bilateral amputations, Knee disarticulation

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: Unknown

20 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial compares two types of prosthetic knees to assess their impact on walking and other activities. The Ossur Power Knee uses a motor to assist movement, while the Conventional prosthetic knee joint (also known as the Ossur Rheo XC) adjusts resistance without a motor. The researchers aim to evaluate the performance of these knees and identify any differences in use between men and women. Individuals with a single above-knee amputation who have used a prosthesis for at least a year may be suitable candidates, particularly if they can walk short distances unaided. As an unphased trial, this study provides an opportunity to contribute to the understanding and improvement of prosthetic technology for future users.

Will I have to stop taking my current medications?

The trial requires that participants are not currently taking medications that affect balance or walking.

What prior data suggests that these prosthetic knees are safe for users?

Previous studies on the Ossur Power Knee have shown mixed results, with some users having positive experiences and others not. The mixed outcomes may stem from the prosthetic's design and operation. However, no specific reports of serious side effects or safety issues have emerged, suggesting it is generally safe to use.

In contrast, the Ossur Rheo XC Knee uses a computer chip to adjust knee movement, unlike the motor-driven Power Knee. The Rheo XC has been available for some time, and no major safety problems have been reported, indicating it is well-tolerated by most users.

Overall, both prosthetic knees have been used in real-world settings without major safety issues. Prospective trial participants should know that these prosthetic knees have been generally safe for users in past studies. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about the Ossur Power Knee because it offers powered flexion and extension, setting it apart from conventional prosthetic knees. This means the Power Knee can actively assist in movements rather than just passively supporting the user, potentially making walking and other activities more natural and less tiring. Unlike standard microprocessor-controlled knees that adjust damping during motion, the Power Knee's active power could lead to better mobility and independence for amputees.

What evidence suggests that this trial's prosthetic knees could be effective for amputation?

Research has shown that the Ossur Power Knee, which participants in this trial may receive, helps users sit, stand, and walk more easily due to its motor that actively assists with movement. This powered knee improves these basic activities compared to regular prosthetics. However, some studies have noted possible downsides, such as reduced agility and slower transitions. Considering these tradeoffs is important when evaluating the Ossur Power Knee.

The Ossur Rheo XC Knee, another option in this trial, is a passive knee with a microprocessor that adjusts resistance to aid movement but lacks a motor. Each option offers distinct benefits, so selecting the right one depends on individual needs and preferences. ^{1 2 5 6 7}

Who Is on the Research Team?

Steven A Gard, PhD

Principal Investigator

Jesse Brown VA Medical Center, Chicago, IL

Are You a Good Fit for This Trial?

This trial is for individuals with a transfemoral amputation, meaning they have had an amputation above the knee. Participants should be current users of a conventional prosthetic knee joint and willing to try out a powered prosthetic knee joint.

Inclusion Criteria

I can walk short distances without help from devices.

My skin is healthy and intact.

I have had one leg amputated above the knee.

Exclusion Criteria

I have had both of my limbs amputated.

I have had a knee disarticulation surgery.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Accommodation

Participants undergo a 1-month accommodation period with each prosthetic knee component

4 weeks

Biomechanical Evaluation

Participants are evaluated for gait, stairs, slopes, and sit-to-stand activities using the Ossur Power Knee and Ossur Rheo XC

4 weeks

Multiple visits for data collection

Follow-up

Participants are monitored for safety and effectiveness after the evaluation period

4 weeks

What Are the Treatments Tested in This Trial?

Interventions

• Conventional prosthetic knee joint
• Ossur Power Knee

Trial Overview

The study is testing the Ossur Power Knee, which uses motors to help in walking and other activities, against the Ossur Rheo XC, which does not use motors but adjusts automatically during movement. The comparison will look at how each affects mobility.

How Is the Trial Designed?

Group I: Ossur Power Knee Experimental Treatment 1 Intervention

Subjects will be fitted with the Ossur Power Knee, which has powered flexion and extension.

Group II: Ossur Rheo XC Knee Active Control 1 Intervention

Subjects will be fitted with the Ossur Rheo XC Knee, which is a conventional microprocessor-controlled knee joint that modulates the amount of damping during flexion and extension.

Conventional prosthetic knee joint is already approved in United States, European Union, Canada for the following indications:

Approved in United States as Conventional prosthetic knee joint for:

• Transfemoral amputation
• Lower limb amputation

Approved in European Union as Conventional prosthetic knee joint for:

• Transfemoral amputation
• Lower limb amputation

Approved in Canada as Conventional prosthetic knee joint for:

• Transfemoral amputation
• Lower limb amputation

Who Is Running the Clinical Trial?

VA Office of Research and Development

Lead Sponsor

Trials

1,691

Recruited

3,759,000+

Published Research Related to This Trial

In a study comparing prosthetic knee systems for U.S. military service members with transfemoral amputations, the Power Knee™ (PK) showed greater peak knee power in the amputated limb during sit-to-stand tasks compared to the C-Leg, suggesting enhanced performance for PK users.

Despite the differences in knee power, both prosthetic systems resulted in greater forces on the intact limb, indicating that while PK may improve certain tasks, it does not significantly reduce impact on the remaining joints compared to the C-Leg.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Comparison of the Power Knee and C-Leg during step-up and sit-to-stand tasks. Wolf, EJ., Everding, VQ., Linberg, AA., et al.[2022]

The development of a passive polycentric knee joint for trans-femoral amputees led to a significant increase in health-related quality of life (HRQL), with physical and mental scores improving by 49% and 46% respectively after 6 months of use.

The prosthetic device demonstrated enhanced performance, achieving a global score of 63, indicating that this affordable knee joint could greatly benefit trans-femoral amputees and should be considered for wider use.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Rehabilitation evaluation of the newly developed polymeric based passive polycentric knee joint. Arun, S., Marbaniang, B., Borgohain, B., et al.[2021]

In a study of 15 active transfemoral amputees, the use of a microprocessor-controlled knee joint significantly improved lower extremity joint kinetics symmetry compared to a passive mechanical knee joint.

Although there were no significant differences in joint kinematics symmetry between the two types of knee joints, the enhanced gait symmetry from the microprocessor-controlled knee may help reduce future musculoskeletal degenerative changes in amputees.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Gait asymmetry of transfemoral amputees using mechanical and microprocessor-controlled prosthetic knees. Kaufman, KR., Frittoli, S., Frigo, CA.[2022]

In a 14-month randomized crossover trial involving 12 participants with transfemoral amputation, the adaptive control knee (Ossur Rheo Knee II) significantly improved comfortable Timed Up and Go (TUG) times and reported physical function compared to passive control knees.

The active control knee (Ossur Power Knee II) showed even greater improvements in TUG times and balance confidence compared to passive control, but it may restrict mobility for middle-aged or older users.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Physical performance and self-report outcomes associated with use of passive, adaptive, and active prosthetic knees in persons with unilateral, transfemoral amputation: Randomized crossover trial. Hafner, BJ., Askew, RL.[2022]

The use of an active powered microprocessor-controlled prosthetic knee (A-MPK) resulted in greater knee range of motion and reduced hip torque during walking compared to a passive microprocessor-controlled prosthetic knee (P-MPK) in four transfemoral amputees, suggesting improved gait mechanics.

A follow-up case study indicated that using the A-MPK for four weeks increased the amputee's confidence and highlighted the importance of adaptation time for optimizing the benefits of the A-MPK.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Assessment of transfemoral amputees using a passive microprocessor-controlled knee versus an active powered microprocessor-controlled knee for level walking. Creylman, V., Knippels, I., Janssen, P., et al.[2018]

The study demonstrated that a powered knee-ankle prosthesis significantly improved weight-bearing symmetry by 42.1% during sit-down movements compared to passive prostheses, indicating enhanced stability for above-knee amputees.

Despite the improvement in weight-bearing symmetry, there was no significant reduction in muscle effort from the intact quadricep muscle, suggesting that while powered prosthetics improve balance, they may not lessen the physical demands on the user's intact limb.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Can a powered knee-ankle prosthesis improve weight-bearing symmetry during stand-to-sit transitions in individuals with above-knee amputations? Hunt, GR., Hood, S., Gabert, L., et al.[2023]

Microprocessor-controlled prosthetic knees (MPKs) significantly reduce falls and fear of falling in limited community ambulators, based on a systematic review of 13 studies involving 2366 patients, with 704 classified as limited community ambulators.

MPKs also improve mobility, walking speed, and patient-reported ambulation, making them a valuable therapeutic option for individuals with transfemoral amputations.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The effect of microprocessor controlled exo-prosthetic knees on limited community ambulators: systematic review and meta-analysis. Hahn, A., Bueschges, S., Prager, M., et al.[2023]

A study involving 10 young adults with unilateral transfemoral amputation found that the weight-activated braking knee resulted in a longer swing-phase duration and greater anterior pelvic tilt compared to the automatic stance-phase lock knee, indicating distinct biomechanical differences between the two prosthetic knee types.

The prolonged swing-phase time for the weight-activated braking knee suggests that it may require more knee unloading to initiate flexion during gait, which could lead to stability issues in early stance-phase and affect overall gait patterns.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Biomechanical responses of young adults with unilateral transfemoral amputation using two types of mechanical stance control prosthetic knee joints. Andrysek, J., García, D., Rozbaczylo, C., et al.[2022]

Citations

1.

jneuroengrehab.biomedcentral.com

jneuroengrehab.biomedcentral.com/articles/10.1186/s12984-025-01729-2

The clinical effects of the Össur Power Knee with phase- ...

Some negative effects of the Power Knee were also observed including reduced agility, slower transitions, and thermal limitations, though some ...

2.

news.umich.edu

news.umich.edu/robotic-knee-prosthesis-advanced-control-algorithm-could-expand-commercial-legs-benefits/

Robotic knee prosthesis: Advanced control algorithm could ...

Paired with custom control software, Össur's powered knee prosthesis helped study participants sit, stand and walk more easily.

3.

clinicaltrials.gov

clinicaltrials.gov/study/NCT05267639

Clinical Outcomes With Passive MPKs vs. Powered ...

This study will focus on investigating the tradeoffs between the commercially available Ossur Power Knee and traditional MPKs to identify the prosthetic knee ...

4.

clinicaltrials.gov

clinicaltrials.gov/study/NCT06194838

NCT06194838 | Clinical Outcomes With Non-Powered vs. ...

The results of this study will (1) provide initial evidence to guide clinical prescription and use of powered knee technologies for K2-level individuals with ...

5.

linkedin.com

linkedin.com/posts/robertdgregg_robotic-knee-prosthesis-advanced-control-activity-7381067301372137472-cr0b

"New study on Össur Power Knee's effects on amputees"

She lost her left hand and her right leg above the knee as well as two-thirds of her blood, and had to be airlifted for emergency surgery. Upon ...

6.

pubmed.ncbi.nlm.nih.gov

pubmed.ncbi.nlm.nih.gov/41024213/

The clinical effects of the Össur Power Knee with phase- ...

Previous studies have demonstrated mixed results, potentially due to a combination of limitations in prosthetic hardware, control algorithms, ...

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trialx.com

trialx.com/clinical-trials/listings/282093/clinical-outcomes-with-non-powered-vs-powered-prosthetic-knees-by-k2-level-amputees/

Clinical Outcomes With Non-Powered vs. Powered ...

The results of this study will (1) provide initial evidence to guide clinical prescription and use of powered knee technologies for K2-level ...