Microprocessor-controlled Prosthetic Knee Research Articles

An enhancement of the Genium™ microprocessor-controlled knee improves safety and different aspects of the perceived prosthetic experience for unilateral and bilateral users.

Bilateral microprocessor-controlled prosthetic knee (MPK) users have unique needs in traversing environmental barriers compared to unilateral users. An enhancement to the Genium™/Genium X3™ MPK which included an updated ruleset, hydraulics, and new bilateral parameter presets was made to improve safety while stumbling and the smoothness of gait for all users while also improving the experience of bilateral users. The purpose of the study was to evaluate the effectiveness of the enhancements in a sample with unilateral and bilateral amputation. A convenience sample of MPK users was recruited from two sites in the USA in two phases. Assessments included the L-Test of Functional Mobility, Activity-specific Balance Confidence Scale, Prosthetic Limb User Survey of Mobility, a study-specific questionnaire, and the Comparative Activities of Daily Living (ADL) Questionnaire. Statistical significance of extracted data was tested with the Wilcoxon Rank-Sum Test for independent data and Wilcoxon Signed-Rank for paired data with an a priori significance level of p < 0.05. Unilateral subjects were age-matched to the group of bilateral subjects for between-groups and within-groups analyses. Twenty-six subjects (n = 26) were enrolled. Stumble frequency reduced 85% from 16.0 ± 39.7 to 2.4 ± 2.3 (p = 0.008) between baseline and final assessment overall. The bilateral group reported 50% (p = 0.009) and 57% (p = 0.009) greater relative improvement in patient-reported ease and safety, respectively, of completing ADLs compared to the unilateral group. The unilateral group reported residual limb pain and low back pain reduced from 2.3 to 1.4 (p = 0.020) and 3.8 to 1.8 (p = 0.027), respectively, whereas the bilateral group did not. Substantial reductions in stumbles, residual limb pain, and back pain were shown overall. These reductions were driven by the unilateral group who also showed improvements in comfort, exertion, and concentration while walking. The enhancements to the knee likely reduced some gait asymmetry for unilateral users. Improvements in patient-reported ease and safety of completing ADLs were shown overall and were driven by the bilateral group. This study shows further improvement in patient experience is achievable through innovation in MPK technology even for patients who appear to be functioning well.

Hip joint and muscle loading for persons with bilateral transfemoral/through-knee amputations: biomechanical differences between full-length articulated and foreshortened non-articulated prostheses

BackgroundCurrently, there is little available in-depth analysis of the biomechanical effect of different prostheses on the musculoskeletal system function and residual limb internal loading for persons with bilateral transfemoral/through-knee amputations (BTF). Commercially available prostheses for BTF include full-length articulated prostheses (microprocessor-controlled prosthetic knees with dynamic response prosthetic feet) and foreshortened non-articulated stubby prostheses. This study aims to assess and compare the BTF musculoskeletal function and loading during gait with these two types of prostheses.MethodsGait data were collected from four male traumatic military BTF and four able-bodied (AB) matched controls using a 10-camera motion capture system with two force plates. BTF completed level-ground walking trials with full-length articulated and foreshortened non-articulated stubby prostheses. Inverse kinematics, inverse dynamics and musculoskeletal modelling simulations were conducted.ResultsFull-length articulated prostheses introduced larger stride length (by 0.5 m) and walking speed (by 0.3 m/s) than stubbies. BTF with articulated prostheses showed larger peak hip extension angles (by 10.1°), flexion moment (by 1.0 Nm/kg) and second peak hip contact force (by 3.8 bodyweight) than stubbies. There was no difference in the hip joint loading profile between BTF with stubbies and AB for one gait cycle. Full-length articulated prostheses introduced higher hip flexor muscle force impulse than stubbies.ConclusionsCompared to stubbies, BTF with full-length articulated prostheses can achieve similar activity levels to persons without limb loss, but this may introduce detrimental muscle and hip joint loading, which may lead to reduced muscular endurance and joint degeneration. This study provides beneficial guidance in making informed decisions for prosthesis choice.

Ergonomics and Field performances of pneumatic, hydraulic, and microprocessor-controlled prosthetic knee prototypes for transfemoral amputee

Ergonomics and Field performances of pneumatic, hydraulic, and microprocessor-controlled prosthetic knee prototypes for transfemoral amputee

The Detection of Compensatory Movements in Gait by Evaluating Plantar Pressure in Transfemoral Amputees

Microprocessor-controlled prosthetic knees (MPKs) improve the safety and functional capabilities of transfemoral amputees, but there is a lack of information on plantar pressure distribution and effects among individuals who have undergone transfemoral amputation of the sound limb. (1) Background: The aim of this study was to determine possible compensatory mechanisms in gait by evaluating intact extremity foot plantar pressure distribution in young MPK prosthesis users. Twenty-one patients with unilateral transfemoral amputation (TFA) and twenty-four healthy individuals were selected for the study. (2) Methods: The WalkinSense system was used to assess different foot plantar pressure distribution parameters as the participants walked at their chosen walking speed. Plantar pressure peaks and activation percentages in the eight foot regions were measured during the gait cycle. (3) Results: The pressure peaks and activation percentages in the sound limb with TFA patients and healthy subjects were measured, and statistically significant differences between the two groups were identified. The 1-, 2-, 3-, 4-, and 6-point sensor activation percentages significantly increased, whereas the 7- and 8-point sensor activation percentages decreased in the sound limb TFA participants compared with the healthy subjects. Peak plantar pressure sensor points 1, 3, 4, and 6 increased in the TFA sound limb foot in relation to healthy individuals, while they decreased in point 8. (4) Conclusion: In this study, with the use of a microprocessor knee joint TF prosthesis, in the evaluation of the underfoot pressure of intact legs, the maximum pressure point shifted to the forefoot, and it was observed that the forefoot and midfoot were more active during walking compared with the control group. This may indicate that gait compensation and plantar flexion in the sound limb are used more forcefully in the gait cycle.

The Kenevo microprocessor-controlled prosthetic knee compared with non-microprocessor-controlled knees in individuals older than 65 years in Sweden: A cost-effectiveness and budget-impact analysis.

Background:Growing evidence suggests that individuals with transfemoral amputation or knee disarticulation using a prosthesis equipped with a microprocessor-controlled knee (MPK) benefit from enhanced mobility and safety, including less falls. In elderly individuals, high mortality rates are assumed to reduce the expected useful life of MPKs, and this raises concerns regarding their economic effectiveness.Objective:To investigate the cost-effectiveness and budget impact of the Kenevo/MPK (Ottobock, Germany) compared with non–microprocessor-controlled knees (NMPKs) in people older than 65 years at the time of transfemoral amputation/knee disarticulation, from a Swedish payer’s perspective.Methods:A decision-analytic model was developed to conduct the economic analysis of the Kenevo/MPK. Model parameters were derived from Swedish databases and published literature. Univariate and probabilistic sensitivity analyses were performed to explore parameter uncertainty.Results:Compared with NMPKs, the Kenevo/MPK reduced the frequency of hospitalizations by 137 per 1,000 person years while the frequency of fatal falls was reduced by 19 per 1,000 person-years in the simulation. Over a 25-year time horizon, the incremental cost-effectiveness ratio was EUR11,369 per quality-adjusted life year. The probability of the MPK being cost-effective at a threshold of EUR40,000 per quality-adjusted life year was 99%. The 5-year budget impact model predicted an increase in payer expenditure of EUR1.76 million if all new patients received a Kenevo/MPK, and 50% of current NMPK users switched to the MPK.Conclusions:Results of the modeling suggest that the Kenevo/MPK is likely to be cost-effective for elderly individuals, primarily because of a reduction in falls.

Design and Assist-As-Needed Control of a Lightly Powered Prosthetic Knee

This paper presents the design of a swing-assist prosthetic knee capable of providing stabilizing passive torques during the stance phase of walking and supplementing the passive swing phase behavior of the prosthetic knee with small active torques. The prosthesis design utilizes a novel actuator which integrates a symmetric multi-chamber hydraulic cylinder and a highly backdrivable linear electromechanical drive system into a single compact package. This actuator is implemented in a self-contained prosthesis design (including batteries and embedded system) which weighs 1.7 kg and is 28 cm in length, making this design comparable in size/mass to commercially available microprocessor-controlled prosthetic knees. The device is controlled using a finite state machine with a novel assist-as-needed controller operating during the swing phase. This assist-as-needed controller supplements a nominally passive swing phase behavior with small amounts of active power to enhance user safety. The device and controller were assessed on a single participant who took part in level ground walking experiments with both the swing-assist prosthesis and his daily-use device. Results indicate that the swing-assist prosthesis increases maximum swing phase knee flexion angle relative to the subject’s daily-use device. Furthermore, the swing-assist prosthesis was shown to automatically vary its assistance across walking speeds.

Impacts of Microprocessor-Controlled Versus Non-microprocessor-Controlled Prosthetic Knee Joints Among Transfemoral Amputees on Functional Outcomes: A Comparative Study.

Introduction: Selecting a prosthetic knee mechanism is an important part of transfemoral (TF) amputee rehabilitation. Prosthetic knee joint selection depends on the users' gait and their energy consumption. This study compares the feedback of transfemoral prosthesis users based on the prosthetic knee design self-reporting responses using the Prosthetic Evaluation Questionnaire (PEQ) outcome measure.Objective: This study aims to assess the impact of using a microprocessor-controlled prosthetic knee (MCPK) compared with a non-microprocessor-controlled prosthetic knee (NMCPK); feedback on the amputee usage can improve the clinical decision for proper prosthetic knee joint selection.Methods: This is a cross-sectional study with a total of 76 adult unilateral transfemoral amputees classified into two groups. The participants in the first group (38) used the MCPK (Genium, Otto Bock, Minneapolis, MN, USA), and the participants in the second group (38) used the NMCPK (hydraulic and total knee joints). Enrolment was based on a sequence of appointments where all participants answered the PEQ, with different subscale questions including utility (UT), sounds (SO), appearance (AP), residual limb health (RL), frustration (FR), perceived response (PR), social burden (SB), ambulation (AM), and quality of life (QoL). PEQ was filled out during the follow-up appointments at the prosthetic clinic through a visual analog scale (VAS). All data entered into a database were analyzed.Result: The MCPK participants have significantly improved utility, appearance, ambulation, and total PEQ score, the same results as the male participants. Middle-adulthood (25-40 years) MCPK participants have a significant p-value in the score of utility, frustration, ambulation, and total PEQ score compared to early-adulthood (18-24 years) and late-adulthood (41-60 years) participants. Also, there was a significant improvement in the p-value in ambulation scores in participants using MCPK with amputations caused by diseases compared to amputations caused by trauma and congenital cause.Conclusion: Transfemoral amputee prosthesis utility, natural gait, and ambulation improved when using MCPK compared to when using NMCPK during prosthetic rehabilitation.

A Retrospective Review of Psychosocial Outcomes After Microprocessor Knee Prescription

ABSTRACT Introduction Microprocessor knees have been shown to improve gait biomechanics and to reduce the frequency of falls, but evidence of their influence on psychosocial health is limited. Study Design Retrospective analysis. Objective The aim of this study was to evaluate the change in psychosocial outcome measures when prosthetic users change from a non–microprocessor-controlled prosthetic knee (NMPK) to a microprocessor-controlled prosthetic knee (MPK). Methods Using validated outcome measures, physical and psychological attributes of 26 MPK users were analyzed using data collected at routine appointments. Baseline data were collected using NMPK limbs first, then compared with data collected 4 weeks and 6 months after initial MPK fitting. Results A significant improvement of 13.7% in Reintegration to Normal Living Index (RNLI) scores was observed after 6 months (P = 0.001). The Patient Health Questionnaire-9 (PHQ-9) demonstrated a 64.6% significant reduction in the presence of depression-like symptoms after 6 months of MPK use (P &lt; 0.001), including four participants who previously scored highly enough to be diagnosed with major depressive disorder. Frequency of falls reduced significantly as well (P &lt; 0.001). Increases in self-selected walking speed were seen in both the 2-minute walk and 6-minute walk tests. Conclusions Significant improvements were seen in all psychosocial outcome measures, indicating participants' psychosocial health improved with the prescription of an MPK despite a lack of clinically important improvements in parallel performance-based outcome measures. Clinical Relevance MPKs are well documented to reduce trips and falls, which is corroborated by this research. However, the psychosocial benefits of MPKs are not documented extensively; this study provides evidence of an improvement in psychological wellbeing in this cohort.

Distribution of joint work during walking on slopes among persons with transfemoral amputation

Persons with above-knee amputation have increased energy consumption and greater difficulty in negotiating uphill and downhill slopes. Walking on slopes requires an adaptation of the positive and negative work performed by the joints of the lower limb to propel the center of mass. Modern prosthetic feet and knees can only partially adapt to changes in inclination, and the redistribution of joint work among persons with above-knee amputation is not described in the literature.Level, upslope and downslope walking (at 5% and 12% inclinations) were investigated for twelve subjects with transfemoral amputation fitted with an Energy Storing And Return foot (ESAR) and a Microprocessor controlled Prosthetic Knee (MPK) versus a control group of seventeen asymptomatic subjects. Lower limb joint and individual limb power and work were compared between prosthetic, contralateral and control limbs.The prosthesis dissipates less energy than the joints of the lower limb of the control group when descending the slope, but the demand on the contralateral limb is limited by a lower speed and step length. The huge deficit of positive work produced by the prosthetic ankle cannot be compensated by the residual hip during level and slope ascent which transfers the demand for energy production to the contralateral limb up to 40% on a 12% slope.This study highlights that prosthetic devices (ESAR foot and MPK) for persons with above-knee amputation present some limitations during slope walking that cannot be compensated by the residual hip and increase the work performed by the contralateral limb.

The effect of microprocessor controlled exo-prosthetic knees on limited community ambulators: systematic review and meta-analysis

Purpose The clinical benefits of microprocessor-controlled prosthetic knees (MPKs) in community ambulators have been well-established. A systematic review in limited community ambulators published in 2014 found benefits in safety, performance-based, and patient-reported outcomes. This work updates the previous analysis to the current state of the published evidence. Methods Systematic review and meta-analysis of the effect of MPKs in limited community ambulators. Results Thirteen research projects presented in 15 publications were identified. Overall validity was “high” in nine studies, “moderate” in three, and “low” in one. The literature described a total of 2366 patients, with 704 classified as limited community ambulators. The use of MPKs in limited community ambulators led to a reduction in falls (SMD g: –0.59; 95% confidence interval (CI) [–0.85, –0.32; I 2=0%]), fear of falling (SMD g: 1.2; 95%CI [0.55, 1.85; I 2=80%]), risk of falling as indicated by the TUG (SMD g: –0.45, 95%CI [–0.87, –0.02; I 2=0%]), an improvement in mobility grade (0.51; 95%CI [0.47,0.55]), self-selected walking speed (SMD g: 0.47; 95%CI [0.14,0.81; I 2=0%]), and patient-reported ambulation (MD 9.32; 95%CI [3.61, 15.02; I 2=7%]), and utility (MD 7.76; 95%CI [2.05–13.47; I 2=0%]). Other outcomes exhibited trends in favor of MPK use or remained insensitive. No outcome was identified favoring non-MPKs. Conclusions These results suggest that MPKs may be considered a valuable therapeutic option in limited community ambulators with a transfemoral amputation. Implications for rehabilitation Above knee amputees may be treated with a large variety of artificial exo-prosthetic knee components. Microprocessor-controlled prosthetic knees have proven to be advantageous and cost effective for community ambulators. The current analysis shows similar effects in safety, mobility, and patient perception also for limited community ambulators. Microprocessor-controlled prosthetic knees are a viable therapeutic option for limited community ambulators.

PMD3 A Microprocessor-Controlled Prosthetic Knee Compared to NON-Microprocessor-Controlled Knees in Individuals Aged over 65 in Sweden: A Cost-Effectiveness and Budget-IMPACT Analysis

PMD3 A Microprocessor-Controlled Prosthetic Knee Compared to NON-Microprocessor-Controlled Knees in Individuals Aged over 65 in Sweden: A Cost-Effectiveness and Budget-IMPACT Analysis

Effects of microprocessor-controlled prosthetic knees on self-reported mobility, quality of life, and psychological states in patients with transfemoral amputations.

This study aimed to determine the effects of the microprocessor-controlled prosthetic knee (MPK) joint on self-mobility, body perceptions, depression, and quality of life in patients with unilateral transfemoral amputations (TFAs). Thirty consecutive patients (28 males, mean age=38.5 years, age range=22-57) who had previously used non-MPKs and who were approved to use swing and stance phase-control MPKs were included in this 12-week clinical study. Before the MPK use and after the three-month follow-up, prosthetic use and locomotor capabilities were evaluated using the Houghton Scale and the Locomotor Capabilities Index (LCI-5), respectively. Body perception was assessed using the Amputee Body Image Scale (ABIS). The depressive symptoms and quality of life were evaluated using the Beck Depression Inventory (BDI) score and the 36-Item Short- Form Health Survey (SF-36), respectively. After MPK use, statistically significant ameliorations were observed in all outcome measures. The basic and advanced LCI-5 increased from 26.7±2.2 and 24.8±5.2 to 27.6±1.2 (p=0.007) and 27±2.1 (p=0.004), respectively. Houghton scores improved from 9±1 to 10.3±0.8 (p=0.000). The ABIS and BDI scores decreased from 43.2±10.9 and 5.7±6.6 to 37.1±8.9 (p=0.000) and 3.8±4.5 (p=0.015), respectively. Also, the SF-36 physical function and vitality subscales increased from 71.2±24.0 and 75.5±14.6 to 85.6±16.6 (p=0.001) and 81.7±14.1 (p=0.015), respectively. MPK use provides significant improvements in the locomotor capabilities, quality of life, and activities of daily living to patients with TFAs as well as improves their body image perceptions and depressive symptoms. Level III, Self controlled study.

Pilot study of the microprocessor-controlled prosthetic knee with a novel hydraulic damper.

A prosthetic knee is the key component of the transfemoral prosthesis. The performance of the prosthetic knee determines the walking ability of transfemoral amputees. This study proposes a microprocessor-controlled prosthetic knee with a novel hydraulic damper and evaluates the performance of the prosthetic knee by gait symmetry index. The homotaxial knee joint with electrical-controlled hydraulic cylinder which adjusts knee flexion and extension damping independently and continuously by single motor was designed. Gait symmetry tests under different walking speeds (0.6m/s, 1.1m/s and 1.6m/s) were conducted to evaluate the performance of the proposed microprocessor-controlled prosthetic knee. The symmetry index values indicated that the stance phase was more asymmetry than swing phase. In the swing phase, the knee angle symmetry was observed in different speeds. The number values of symmetry index were smaller than 15% in swing phase. The proposed microprocessor-controlled prosthetic knee could meet the demands of walking.

Cortical brain activity in transfemoral or knee-disarticulation prosthesis users performing single- and dual-task walking activities.

IntroductionWalking with a prosthesis while performing secondary tasks increases demand on cognitive resources, compromising balance and gait. This study investigated effects of a secondary task on patterns of brain activity and temporospatial gait parameters in individuals using a prosthesis with or without a microprocessor-controlled prosthetic knee(MPK) and controls.MethodsA cross-sectional study with repeated measures was performed. Twenty-nine individuals with amputations and 16 controls were recruited. Functional near-infrared spectroscopy was used to evaluate changes in oxygenated and de-oxygenated haemoglobin in the prefrontal cortex and temporospatial variables during single-and dual-task walking.ResultsDifferences in brain activity were observed within the MPK-group and controls without changes in temporospatial parameters. The Trail-Walking test was associated with highest levels of brain activity in both groups. No differences were observed between single- and dual-task walking in the non-MPK-group (p > 0.05). The Non-MPK and the MPK-group recorded higher levels of brain activity than controls during single-task walking and poorer results on temporospatial variables compared to controls.ConclusionsFor the MPK-group and controls, introduction of a secondary task led to an increase in brain activity. This was not seen in the Non-MPK-group. Significant differences in brain activity were observed in the absence of changes in temporospatial parameters.

Characteristic features and usefulness of microprocessor-controlled prosthetic knees

Characteristic features and usefulness of microprocessor-controlled prosthetic knees

RHEO KNEE: Microprocessor-controlled prosthetic knee joint with AI and MR actuator

RHEO KNEE: Microprocessor-controlled prosthetic knee joint with AI and MR actuator

Transitioning to a microprocessor-controlled prosthetic knee: Executive functioning during single and dual-task gait.

Walking with a prosthesis requires substantial concentration on behalf of the user and places increased demands on executive functions. Little is known of the effects that prosthetic knee joint prescription may have on executive functioning. Evaluate executive functioning in trans-femoral prosthesis users during single and dual-task walking, before and after they transition to a Microprocessor-controlled prosthetic knee unit. Multiple case-study design. Single and dual task gait was evaluated while recording cortical brain activity. Testing occasion 1 occurred prior to participants receiving their microprocessor-controlled prosthetic knee, while testing occasion 2 was conducted a minimum of 8 months after they had been fitted with an microprocessor-controlled prosthetic knee. During single-task level walking and walking while performing a dual-task key finding test, executive functions, measured as the relative haemodynamic response in the frontal cortex, reduced for most, but not all participants after transitioning to an Microprocessor-controlled prosthetic knee. There did not appear to be any difference when participants performed a trail walk test. Results suggest Microprocessor-controlled prosthetic knee prosthetic knees may have a positive effect on executive functioning for some individuals who have undergone a lower-limb amputation. A larger, longitudinal study with careful control of extraneous variables (e.g. age, training) is needed to confirm results and determine causality. This article provides some evidence to suggest that prosthetic prescription may influence executive functioning and that microprocessor-controlled prosthetic knee mechanisms may reduce cognitive effort when walking.

A Comparison of Control Strategies in Commercial and Research Knee Prostheses.

To provide an overview of control strategies in commercial and research microprocessor-controlled prosthetic knees (MPKs). Five commercially available MPKs described in patents, and five research MPKs reported in scientific literature were compared. Their working principles, intent recognition, and walking controller were analyzed. Speed and slope adaptability of the walking controller was considered as well. Whereas commercial MPKs are mostly passive, i.e., do not inject energy in the system, and employ heuristic rule-based intent classifiers, research MPKs are all powered and often utilize machine learning algorithms for intention detection. Both commercial and research MPKs rely on finite state machine impedance controllers for walking. Yet while commercial MPKs require a prosthetist to adjust impedance settings, scientific research is focused on reducing the tunable parameter space and developing unified controllers, independent of subject anthropometrics, walking speed, and ground slope. The main challenges in the field of powered, active MPKs (A-MPKs) to boost commercial viability are first to demonstrate the benefit of A-MPKs compared to passive MPKs or mechanical non-microprocessor knees using biomechanical, performance-based and patient-reported metrics. Second, to evaluate control strategies and intent recognition in an uncontrolled environment, preferably outside the laboratory setting. And third, even though research MPKs favor sophisticated algorithms, to maintain the possibility of practical and comprehensible tuning of control parameters, considering optimal control cannot be known a priori. This review identifies main challenges in the development of A-MPKs, which have thus far hindered their broad availability on the market.

Design and Evaluation of a Novel Microprocessor-Controlled Prosthetic Knee

Transfemoral amputees demand a mechatronic lower limb prosthesis as technical substitute for restoring their gait functions. Prosthetic knee is the key component of a transfemoral prosthesis. The performance of the prosthetic knee determines the walking ability of the transfemoral amputee. This study proposed a novel microprocessor-controlled prosthetic knee with hydraulic damper and evaluated the performance of the prosthetic knee by function simulation and evaluation platform. The prosthetic knee with electrical-controlled hydraulic cylinder that could modulate knee flexion and extension damping properties independently and continuously by single motor was designed. Gait phase identification system based on knee angle sensor, inertial measurement units mounted on thigh connector and shank and force transducer embedded in shank was proposed. Gait phase identification and damping control strategy were determined by typical gait events during walking. Speed adaption and gait symmetry tests were conducted with a customized gait simulator to evaluate the performance of the proposed microprocessor-controlled prosthetic knee. The angle trajectories of the prosthetic knee were similar under a range of walking speeds. While the symmetry index values indicated that the stance phase was more asymmetry than swing phase, the peak swing flexion knee angles were consistently controlled between 60-70 degrees under different speeds. The knee angle symmetry was observed in different speeds during swing phase. It is suggested that the proposed microprocessor-controlled prosthetic knee could meet the fundamental demands of walking with smooth angular transition across different walking speeds.

Comparative biomechanical evaluation of two technologically different microprocessor-controlled prosthetic knee joints in safety-relevant daily-life situations.

Safety-relevant gait situations (walking on stairs and slopes, walking backwards, walking with small steps, simulated perturbations of swing phase extension) were investigated in a motion analysis laboratory with six unilateral transfemoral amputees using two different microprocessor-controlled prosthetic knee joints (Rheo Knee XC, C-Leg). A randomized crossover design was chosen. The study results imply that the performance and safety potential of a microprocessor-controlled knee joint can be associated with the individual control algorithms and the technological concepts that are implemented to generate motion resistances for controlling flexion and extension movements. When walking with small steps, advantages of the "default swing" concept used in the Rheo Knee XC were identified due to a highly reproducible swing phase release. However, when walking backwards, this concept may lead to an uncontrolled knee flexion which partly resulted in falls. When walking down stairs, walking on slopes or while recovering from a stumble after perturbations of the swing phase extension, the C-Leg demonstrated a reliable prosthetic side load-bearing capacity resulting in reduced loading on the residual body. In contrast, the Rheo Knee XC required increased compensatory movements of the remaining locomotor system in order to compensate for reduced load-bearing and safety reserves.