Medical Policy

Subject:  Microprocessor Controlled Lower Limb Prosthesis
Policy #:  OR-PR.00003Current Effective Date:  01/13/2015
Status:ReviewedLast Review Date:  11/13/2014


This document addresses the use of microprocessor controlled lower limb prostheses including, but not limited to, knee prosthesis (such as the Otto-Bock C-Leg device®, the Genium™ Bionic Prosthetic System, the Ossur RheoKnee®, and the Endolite Intelligent Prosthesis®) and foot-ankle prosthesis (such as the Proprio Foot® and the PowerFoot BiOM).

Position Statement

Medically Necessary: 

The use of a microprocessor controlled lower limb prosthesis (for example, Otto-Bock C-Leg device®, Otto-Bock Genium™ Bionic Prosthetic System, the Ossur RheoKnee® or the Endolite Intelligent Prosthesis®) is considered medically necessary for transfemoral (above knee) and knee disarticulation amputees when all of the criteria set forth in (A) and (B) below have been met:

  1. Selection criteria:
    1. Individual has adequate cardiovascular reserve and cognitive learning ability to master the higher level technology and to allow for faster than normal walking speed; and
    2. Individual has demonstrated the ability to ambulate faster than their baseline rate using a standard prosthetic application with a swing and stance control knee; and
    3. Individual has a documented need for daily long distance ambulation (for example, greater than 400 yards) at variable rates.  (In other words, use within the home or for basic community ambulation is not sufficient to justify the computerized limb over standard limb applications); and
    4. Individual has a demonstrated need for regular ambulation on uneven terrain or regular use on stairs.  Use of limb for limited stair climbing in the home or place of employment is not sufficient to justify the computerized limb over standard limb applications.
  2. Documentation and performance criteria:
    1. Complete multidisciplinary assessment of individual including an evaluation by a trained prosthetic clinician.  The assessment must objectively document that all of the above selection criteria have been evaluated and met. 

Not Medically Necessary: 

The use of microprocessor controlled leg prosthesis is considered not medically necessary in all other cases, including when the criteria above have not been met.

Investigational and Not Medically Necessary: 

The use of a microprocessor controlled foot-ankle prosthesis (for example, Proprio Foot® or the PowerFoot BiOM) is considered investigational and not medically necessary for all indications.


At this time, the available peer-reviewed published literature addressing the clinical benefit of microprocessor controlled lower limb prostheses is mostly limited to non-randomized controlled clinical trials, and case series of limited size.  Additionally, the majority of these studies have involved highly selected subjects who were otherwise in good health.  

Microprocessor Controlled Knee Prosthesis

One publication by Hafner and others (2007) reports the findings of a small, non-randomized, cross-over controlled design study in which each subject was exposed to two different prosthetic limb conditions (mechanical and microprocessor controlled C-Leg) twice during the trial.  This study included 21 subjects, each of whom used both a standard mechanical knee and lower limb prosthesis and the C-Leg microprocessor controlled prosthesis.  Subjects were recruited for participation from a local amputee population.  Seventeen subjects completed the study.  Subjects were told at the time of enrollment that they would be allowed to keep the test prosthesis whether or not they completed the trial.  The subjects began the trial with a 2 month period using their standard prosthesis followed by an activity assessment and functional, performance and subjective perception evaluation.  Next, all subjects used the microprocessor controlled prosthesis until acclimation was demonstrated.  This was then followed by a 2 month acclimation period with the microprocessor controlled prosthesis, ending with an activity assessment and functional, performance and subjective perception evaluation.  Subjects were then reverted back to the standard prosthesis for 2 weeks and again an activity assessment and functional, performance and subjective perception evaluation was done.  In the final stage of the trial, participants were allowed to use either one or both prosthetic devices over a 4 month period.  Daily use and activity levels were measured for each device.  The study concluded with a final activity assessment and functional performance and subjective perception evaluation with the microprocessor controlled device.  A variety of objective and subjective outcome measures were reported.  The authors reported no significant differences between the two prosthetic devices in terms of daily activity as measured by mean daily step frequency and mean estimated step distance, in performance on level or varied surfaces, or in cognitive demand during use of the devices.  They did note a significant improvement with the C-Leg prosthesis in subjects' Stair Assessment Index (SAI) scores, time to descend scores, and a surveyed preference for the microprocessor controlled C-Leg as compared with a mechanical prosthetic knee.  There was no difference noted in ascending stairs, but self reported frequency of stumbles and falls was lower for the C-Leg prosthesis.  Limitations of this study include its small size, lack of outcome comparisons to a group randomized to continued use of a standard prosthesis, and lack of control of the type of mechanical prosthesis used.  In addition, the period of time allowed for the subject to revert back to a standard prosthesis (2 weeks) for a functional assessment prior to the 4 month combined use measures was quite limited.

An article by Williams and colleagues (2006) describes a randomized two-group crossover design study of C-Leg versus a standard hydraulic knee prosthesis (Mauch SNS® knee).  Subjects were given a 3 month acclimation period for each device prior to testing.  This study was not blinded and was hampered by a significant drop-out rate (56%) that left only 8 participants in the evaluable study population.  The findings concluded that in non-demanding walking conditions with experienced amputees, participants reported the C-Leg® required less cognitive attention than the non-computerized knee.  However, this subjective experience did not translate into improved performance on neuropsychologic screening instruments or walking speed.

In another report of the same trial (Orendurf, 2006) the authors report that they found no significant difference between the groups in either oxygen efficiency or gait efficiency.  It is noted in the discussion section of this article that the programming of each C-Leg requires a high degree of tailoring to meet the needs of the user.  The authors comment that the parameters that were used by each of the study participants varied widely, with some preferring their C-Leg to operate in a manner not too dissimilar to that of a standard non-computerized limb, and others preferring significantly different functional parameters.  With this degree of variation, even within such a small study population, it would indicate that a much larger study population should be used in further studies of the C-Leg in order to control for this potential source of bias.

A non-randomized cross-over study conducted by Kaufman and colleagues (2007) compared the C-Leg to the standard hydraulic prosthesis in gait and balance parameters.  The study included 15 participants, who were allowed an average of 4.5 months of acclimation time with each device.  The authors indicate that there was a significant (p<0.01) improvement in objective, standardized measures of both gait (knee flexor movement) and balance (Sensory Organization Test) with the computerized prosthesis.  The investigators point out that the study included a select group of healthy, highly effective ambulators with no additional musculoskeletal conditions.  It is unclear what impact the use of computerized prosthetic knee devices may have on individuals with lower functional classifications.

Seymour and colleagues published a study comparing energy expenditure, obstacle course negotiation and quality of life (QOL) measures in 10 highly effective healthy ambulators who use both a C-Leg and a non-computerized prosthesis (2007).  This study had a 23% drop out rate.  A subset of participants (10 of 13) in this study underwent an 8 minute energy consumption test on a treadmill using one of their prostheses, and then again using the other device after a 10 minute rest.  They were then asked to undergo a walking obstacle course 8 times, 4 holding a laundry basket containing a 10 lb. weight, and 4 times unencumbered.  Finally, they were asked to complete a standardized quality of life questionnaire (SF-36v2).  The authors report a statistically significant lower energy consumption rate for participants when wearing their C-Leg devices at both typical and fast paces.  On the obstacle course, statistical differences were noted in the number of steps taken, elapsed time, and the number of times participants stepped out of bounds during the unencumbered portion of the trial.  During the encumbered trial, the elapsed time (11.5 sec vs. 15.5 sec) was shorter for the C-Leg prosthesis group (p=0.007).  No stumbles or falls were reported in either group.  The results of the QOL questionnaire associated with wearing the C-Leg indicated that the participants were at or above the normative data available for the general population. 

A study by Kahle and colleagues (2008) investigated the impact of the C-Leg on several functional parameters, including stumbles, falls, performance in walking and stair descent and QOL.  The study involved 21 subjects, with 19 completing the study, and utilized a simple pre-test post-test design.  Participants in the study had a wide variation in physical status and health, but were all community ambulators.  Some participants utilized assistive devices for ambulation.  This is the first published study to include a mixed population.  The authors report significant improvement in the number of stumbles (p=0.006), but no significant improvement in the number of falls.  No statistical analysis was provided for either walking or stair descent performance.  Finally, there was a significant improvement (20%, p=0.007) in QOL scores with the C-Leg prosthesis.

Theeven and others (2011) conducted a small randomized, controlled cross-over trial that was significantly different from the previously discussed studies in two respects.  First, instead of including only highly selected healthy amputee subjects, their study only included individuals who were classified as Medicare Functional Classification Level-2 (MFCL-2), which represents an intermediate capacity for physical functioning, commonly termed as "limited community ambulatory."  Second, this study not only compared standard mechanical prosthetic devices to microprocessor controlled devices, but also compared two microprocessor controlled devices with one another.  The study design called for each participant to wear a different prosthesis for sequential week-long periods, with testing at the end of each week.  All participants wore their standard mechanical prosthesis for the first week, followed by the two microprocessor controlled prosthetic devices (either the Otto-Bock C-leg, or the Otto-Bock C-Leg Compact).  A total of 41 subjects were randomized, but only 28 subjects (68%) completed the trial. 

The authors further stratified study subjects into three groups ("High", "Intermediate", or "Low") based on expert opinion regarding functional levels within the MFCL category.  Subject performance on the ADAPT testing circuit was further stratified by specific sections of the test.  The ADAPT test circuit presents three separate sets of physical challenges, each addressing discrete subsets of skills or abilities that become increasingly challenging.  Activity Subset 1 (AS1) focuses on activities that require adequate balance, Activity Subset 2 (AS2) focuses on actions that challenge muscle strength and weight distribution, and Activity Subset 3 (AS3) focuses on actions dependent upon prosthesis-related and cognitive skills.  The authors reported a large variation in the functional performance level seen within the study's MFCL-2 population, as well as between prosthetic devices.  The Low functional level subjects demonstrated no benefit from a microprocessor controlled prosthesis at any level of the test.  Both Intermediate and High group subjects were reported to have significant improvements in performance of AS2 activities, with the High group performing significantly better than the Intermediate group.  For AS3 activities, only the High group demonstrated any benefit.  Inter-device comparison found that the High group performed significantly better with both computerized prostheses in AS1, but none in AS2.  In AS3, the High group had significantly better times only when subjects wore the C-Leg Compact Device, but not the standard C-leg.  In contrast, the intermediate group only had significant improvements in AS2 with the standard C-leg, but not with the more advanced C-Leg compact device. 

The authors conclude that there is a wide disparity in functional levels within the MFCL-2 classification.  They also note that despite the overall data showing benefit by functional levels, performance at the individual level was significantly variable across functional levels.  Additionally, there was a significant variation in achieved benefit depending upon device type.  In this study, the data are limited by the small study sample.  Also, the authors note that the choice of break-in period may have a significant impact on the results, and longer acclimation times may significantly change the results.  This is the first study looking at the use of microprocessor controlled knee prostheses in lower functioning subjects in a rigorous manner.  The results showed significant variation in performance between individuals and unexpected results with regard to outcomes between device types.  It highlights that there are still many questions left to address with regard to the benefits derived from these devices. Further research is warranted.

Another group published the results of testing in a group of MFCL-2 subjects (Burnfield, 2012).  This study investigated the sequential use of standard mechanical prostheses followed by the C-Leg device in 10 subjects who were asked to complete a series of tasks while measurements were taken on gait, stride, motion analysis, timed functional assessments along with questionnaires and EMG.  The authors noted significantly better performance with the C-Leg with regard to ramp ascent and descent and intact limb function.  Intact limb function improvements were used as a proxy measure for stability and user confidence since longer stride and a more regular gait are indicative of prosthetic confidence and comfort.  EMG data was not of sufficient quality to allow proper analysis.  The Timed Up and Go (TUG) test, which measures physical function during a specified series of tasks, showed significant improvement in the C-Leg group.  The results of the Prosthetic Evaluation Questionnaire (PEQ), Activities-specific Balance Confidence Scale (ABC) and the Houghton Scale were mixed, with the PEQ and ABC demonstrating significant benefits with the C-Leg, but not on the Houghton Scale.  This study supports some of the positive findings mentioned earlier in the Theeven trial, but further study is needed to fully understand the impact of microprocessor controlled knee prostheses in the MFCL-2 population.

As discussed earlier in the Theeven study, the authors noted significant differences between specific microprocessor controlled knee prostheses.  This question was further investigated by Bellmann and colleagues, who compared performance parameters of the C-Leg vs. the Genium device (2012).  This study enrolled 11 MFCL-3-4 C-Leg users who were put through a battery of tests while using their own C-Leg device.  Subjects were then introduced to the Genium device, which was attached to their own socket and foot prosthesis.  They were then given approximately 24 hours to accommodate to the new prosthesis before being given a battery of tests.  The authors reported significant benefits of the Genium device over the C-Leg in many measures, including foot loading, sway, step symmetry, and knee flexion during a variety of activities.  However, the very short acclimation time and very small sample size of this study do not allow the results to be generalized to a wider population. 

A small, non-randomized controlled trial involving 15 K3/4 ambulatory subjects was published by Highsmith in 2014.  Each participant was subjected to a series of six balance tests with both a standard knee prosthesis and then with the C-Leg.  The trials involved the use of the Sensory Organization Test (SOT) to assess sensory dependence.  The six different tests involved evaluations under pre-specified conditions with varying balance challenges with their standard prosthesis, followed by an accommodation period with the C-leg and repeat testing.  A significant 3% increase in reliance on somatosensory system input (p=0.047) was reported while using the C-Leg vs. a standard prosthesis.  There was a statistically significant (33%) reduction in the number of falls when using the C-Leg (p=0.03).  Standard prosthesis use resulted in 21 falls among 7 subjects (average, 1.4 ± 2.3 falls per person) compared with 14 falls among 4 subjects (average 0.9 ± 2.1 falls per person) while utilizing the C-Leg.  This comparison's effect size was small.  No data representing real-life use of the prosthesis was reported.

Eberly (2014) reported on another non-randomized controlled trial involving 10 K2 ambulatory subjects with a mean age of 62 years.  Investigators evaluated each subject for stride characteristics, kinematics, kinetics, and electromyographic activity on a 10 meter walkway with both their standard prosthesis and then with the C-Leg Compact, the latter after a 3 month acclimation period.  Subjects were required to walk the 10 meter walkway at a self-selected customary comfortable walking pace and then at a self-selected customary fast walking pace.  The results indicated approximately 20% improvement in walking speed with the C-leg vs. the control prosthesis in both the free walking phase (p=0.002) and the fast walking phase (p=0.000).  This was attributed to increases in both stride length (12% - 14%; p=0.003) and cadence (9% - 10%; p=0.001).  The peak external ankle dorsiflexion moment in late stance increased by more than 20% while walking with the C-Leg vs. the standard prosthesis during both free (p=0.001) and fast (p=0.008) walking.  Walking with the C-Leg produced modestly higher tibialis anterior activity in the intact limb (6% - 8% maximal voluntary contraction [MCV] increase) and moderately more intense lower gluteus maximus activity (19% MVC increase) in the prosthetic limb in both free and fast walking compared to walking with the standard prosthesis (p<0.05).  There were no significant differences between the prostheses in mean EMG activity of the remaining muscles during free or fast walking.

Finally, Theeven and colleagues (2013) published a systematic review of the available literature addressing microprocessor controlled prosthetic knee joints.  A total of 37 studies and 72 outcome measures were identified and included in the study.  They reported that a majority (67%) of the outcome measures addressed the body functions component of the International Classification of Functioning, Disability and Health (ICF), which measures and describes the anatomy and physiology/psychology of the human body.  This component is commonly used to quantify the level of impairment present.  Measurement of how microprocessor controlled prosthetic knee joints affect an individual's actual performance in daily life was reported in only 31% of studies.  Also noted was that the available research primarily focused on young, fit and active persons.  Their findings conclude with the comment that scientifically valid evidence regarding the performance of persons with a microprocessor controlled prosthetic knee joint in everyday life is limited.

Although the evidence continues to evolve, it is reasonable to consider microprocessor controlled lower limb prostheses appropriate for a select group of individuals meeting strict criteria for fitness, health and daily utilization expectations.  However, these devices may not be appropriate for all potential users.  Since the device produces definite but marginal improvements in functional capacity by reducing oxygen consumption and improving walking speed and safety when ambulating in more challenging environments (e.g., long distances, uneven terrain, regular use of stairs) the device is appropriate for users who face those challenges regularly.  In addition, the device requires substantial training to allow for faster than normal walking speed and a user should have adequate cognitive learning ability to master the higher level technology.  The criteria set forth above identify the potential users for whom the device may represent an improvement in functional capacity.

Microprocessor Controlled Foot and Ankle Prosthesis

Published peer-reviewed evidence addressing the use of microprocessor controlled foot-ankle prosthesis is limited.  One small study involved 12 subjects and measured socket pressures in individuals undergoing gait analysis during various locomotion tasks using the Proprio Foot (Ossur) for five walking conditions with and without the device's ankle adaptation mode (Wolf, 2009).  The study concluded that the adaptive ankle-foot prostheses favorably altered joint kinetics and stump pressures on stairs and ramps. 

A second study involved 32 subjects, 16 healthy controls and 16 transtibial amputees using the Proprio Foot (Alimusaj, 2009).  The subjects underwent three-dimensional (3D) gait analysis on stairs.  Kinematics and kinetics of the lower limbs were compared during stair ascent and descent with the prosthetic foot set to a neutral ankle angle and then with an adapted dorsi-flexion ankle angle of 4 degrees.  Comparisons were also made between experimental group subjects and control subjects.  The study concluded that for both stair ascent and descent, the prosthesis resulted in an improvement in kinematic and kinetic measures of the knee with an increase of knee flexion and increase of the knee stability during stance.  

Fradet and colleagues (2010) describe a nonrandomized controlled study involving 16 transtibial amputee subjects using the Proprio Foot and 16 healthy controls.  All participants underwent conventional 3D gait analysis while walking up and down a ramp. The authors reported that subjects, when using the foot ankle prosthesis in adaptive mode, exhibited more physiologic kinematics and kinetics of the lower limbs during ramp ascent but not during ramp descent.  Additionally, subjects using the prosthesis in adaptive mode reported subjective feelings of being safer during ramp descent.  

Herr and colleagues (2011) conducted a small study investigating the metabolic energy costs, preferred velocities, and biomechanical patterns in 7 unilateral transtibial amputees using the Proprio Foot and 7 non-amputee controls.  The experimental group was tested using both a bionic prosthesis (PowerFoot BiOM) and their own passive-elastic prosthesis.  The authors reported that compared with the passive-elastic prosthesis, the bionic prosthesis decreased metabolic cost by 8%, increased trailing prosthetic leg mechanical work by 57% and decreased the leading biological leg mechanical work by 10%, on average, across walking velocities of 0.75-1.75 m s(-1).  Use of the bionic prosthesis also increased preferred walking velocity by 23%.  They concluded that the bionic prosthesis resulted in metabolic energy costs, preferred walking velocities and biomechanical patterns that were not significantly different from people without an amputation.  However, due to the small study size it is unclear whether or not these results would be seen in the general population.

In 2014, Darter reported the results of a small non-randomized study involving 6 subjects who performed treadmill walking tests using their customary prosthesis, the Proprio Foot in its "on" setting (Pon), and lastly, the Proprio Foot in the "off" setting (Poff).  Through the study, the slope of the treadmill was changed to 3 different slopes, -5 º, 0º, and +5 º.  The results included the observation that metabolic energy expenditure, energy cost for walking, and rating of walking difficulty were not statistically different between the Pon and Poff setting for all tested slopes.  However, for slope descent, energy expenditure and energy cost for walking improved significantly by an average of 10% - 14% for both the Pon and Poff compared to the customary limb.  Walking difficulty also improved with slope descent for both the Pon and Poff compared to the customary device.  An improvement with slope ascent was found for Pon compared to the customary limb only.  The authors concluded that adaptive ankle motion provided no meaningful physiological benefit during slope walking but was less demanding than the customary device for slope descent.

At this time, further study is needed to establish a meaningful clinical outcome benefit of the Proprio Foot over the conventional ankle-foot prosthesis.

Currently there is no peer-reviewed published evidence addressing the clinical efficacy of the PowerFoot BiOM microprocessor controlled foot-ankle prosthesis.  Such information is necessary to properly evaluate the impact of this device.


Prostheses are devices that are used to replace or compensate for the absence of a body part.  Such absence may be present at birth or due to amputation as the result of illness or trauma.  Prosthetic devices have been used to replace body parts from individual fingers to entire limbs.  Additionally, prostheses may include replacements for other body parts including breasts, eyes, and teeth.  There are a wide variety of prostheses for the replacement of limbs made from various materials using a wide range of technologies.

For prostheses used to replace lower limbs where the leg is missing from the knee or above, there is a need for a device to replace the normal function of the knee.  In people with intact legs, the knee naturally and automatically adjusts its action to the speed and stride of the person.  Conventional prosthetic legs use a pneumatic or hydraulic return mechanism to mimic the natural pendulum action of the knee.  This mechanism is usually set by a prosthetist to work at the individual's normal walking speed and does not allow any room for variation in speed.  Changes in an individual's walking speed require the individual to compensate for any delay in knee action through a variety of means including altering stride length and body position, among others.  Such maneuvers lead to an abnormal gait and require extra effort and concentration for what is normally an unconscious act.

Microprocessor controlled lower limb prostheses for the transfemoral amputee use computer-controlled mechanisms to detect step time and alter prosthetic function such as knee extension level to suit walking speed or angle of the terrain.  More advanced models, such as the Otto-Bock C-Leg®,  have multiple sensors that gather and calculate data on various parameters such as the amount of vertical load, ankle movement, and knee joint movement in an attempt to mimic more natural leg function to provide stability and gait fluidity as needed on uneven terrains and/or during sports activities.  The claimed advantages of computerized leg prosthesis include a decreased level of effort in walking, improved symmetry of movement between legs leading to more natural movement, and the avoidance of falls.

For individuals who have lost a limb below the knee, there is a need for a device to replace the function of the ankle and foot.  Stair ambulation is limited in the transtibial amputee due to the neutral and fixed ankle position which exists in traditional prosthetic ankles.  Under study are newer prosthetic ankles which adjust the foot-ankle angle during the swing phase using sensor and microprocessor technologies to identify sloping gradients and the ascent or descent of stairs after the first step.  Users can place the foot fully on a step when climbing or descending stairs and it will automatically adapt the ankle position to enable the next step.  On ramp ascent and descent, adaptation begins on the second step and the device makes small adjustments until it reaches the degree of slope of the ramp.  The Proprio Foot® is one such "quasi-passive" device.  The device is passive since no power is generated through the ankle in stance.  The device is also said to be designed to dorsiflex, or bring the toes closer to the shin, during the swing phase to improve ground clearance, improve gait symmetry and reduce the likelihood of falls.  Other claims include the device's ability to assist in standing from a seated position and plantar (bottom of the foot) flexion when kneeling, sitting and lying down.  Early pilot studies suggest that both during stair ascent and descent, the Proprio Foot improves knee flexion kinematics.  The weight of the Proprio Foot device is more than twice the weight of a conventional ankle-foot prosthetic such as the LP Vari-Flex (995g versus 405g).  Concern has been raised that because of its weight, the Proprio Foot might not benefit amputees with limited endurance and knee musculature.

Also under study are active prosthetic ankle prostheses which do generate power during the ankle stance.  Early results are said to be promising, but these devices are bulky and of considerable weight due to the motor and batteries needed to generate power. 

Another type of microprocessor-controlled foot-ankle prosthetic device, the PowerFoot BiOM, is proposed to simulate the natural function of the foot by simulating the action of the ankle, Achilles tendon and calf muscles to move the individual forward when they step.  These devices utilize various sensors in the ankle and foot to detect foot position, direction, and force of movement.  This data is analyzed by several microcomputers that translate it into instructions for a motor-activated spring device in the sole of the prosthesis. The loaded spring device is released as the sensor detects that the user is taking a step forward, forcing the ball of the foot downwards and propelling the foot forward. The spring mechanism reloads itself in-between steps. This device uses batteries to operate this system and requires daily recharging.

The FDA classified the Proprio Foot as a Class I device and the PowerFoot as a class II device, both exempt from requirements for pre-market notification by submission and FDA review of a 510(k) clearance.  This is based on the level of active assistance provided and the perceived risk associated with these devices.


Computerized leg prosthesis: A prosthetic device for individuals with some degree of leg amputation which uses a computer microprocessor to adapt prosthetic function to environmental conditions that impact locomotion.

Kinematics: A study of motion without regard to the forces present; mathematical methods to describe motion.

Prosthesis: For the purposes of this document, a device used to replace or compensate for the absence of a limb.  Prostheses may be artificial replacements for a wide variety of body parts.


The following codes for treatments and procedures applicable to this document are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member. 

When services may be Medically Necessary when criteria are met:

L5856Addition to lower extremity prosthesis, endoskeletal knee-shin system, microprocessor control feature, swing and stance phase, includes electronic sensor(s), any type
L5857Addition to lower extremity prosthesis, endoskeletal knee-shin system, microprocessor control feature, swing phase only, includes electronic sensor(s), any type
L5858Addition to lower extremity prosthesis, endoskeletal knee-shin system, microprocessor control feature, stance phase only, includes electronic sensor(s), any type
L5859Addition to lower extremity prosthesis, endoskeletal knee-shin system, powered and programmable flexion/extension assist control, includes any type motor(s)
ICD-9 Diagnosis[For dates of service prior to 10/01/2015]
 All diagnoses, including, but not limited to, the following:
897.2Traumatic amputation of leg, unilateral, at or above knee, without mention of complication
897.3Traumatic amputation of leg, unilateral, at or above knee, complicated
897.6-897.7Traumatic amputation of leg, bilateral [when specified at or above knee]
V49.76Lower limb amputation status, above knee
ICD-10 Diagnosis[For dates of service on or after 10/01/2015]
 All diagnoses, including, but not limited to, the following:
S78.111DComplete traumatic amputation at level between right hip and knee, subsequent encounter
S78.111SComplete traumatic amputation at level between right hip and knee, sequela
S78.112DComplete traumatic amputation at level between left hip and knee, subsequent encounter
S78.112SComplete traumatic amputation at level between left hip and knee, sequela
S78.119DComplete traumatic amputation at level between hip and knee, unspecified side, subsequent encounter
S78.119SComplete traumatic amputation at level between right hip and knee, unspecified side, sequela
S88.011DComplete traumatic amputation at right knee level, subsequent encounter
S88.011SComplete traumatic amputation at right knee level, sequela
S88.012DComplete traumatic amputation at left knee level, subsequent encounter
S88.012SComplete traumatic amputation at left knee level, sequela
S88.019DComplete traumatic amputation at knee level, unspecified side, subsequent encounter
S88.019SComplete traumatic amputation at knee level, unspecified side, sequela
Z89.611Acquired absence of right leg above knee
Z89.612Acquired absence of left leg above knee
Z89.619Acquired absence of unspecified leg above knee

When services are Not Medically Necessary:
For the procedure codes listed above when criteria are not met, or when the code(s) describes a procedure indicated in the Position Statement section as not medically necessary.

When services are Investigational and Not Medically Necessary:

L5969Addition, endoskeletal ankle-foot or ankle system, power assist, includes any type motor(s) [when specified as addition to microprocessor controlled ankle-foot system]
L5973Endoskeletal ankle-foot system, microprocessor controlled feature, dorsiflexion and/or plantar flexion control, includes power source
ICD-9 Diagnosis[For dates of service prior to 10/01/2015]
 All diagnoses
ICD-10 Diagnosis[For dates of service on or after 10/01/2015]
 All diagnoses

Peer Reviewed Publications:

  1. Alimusaj M, Fradet L, Braatz F, et al. Kinematics and kinetics with an adaptive ankle foot system during stair ambulation of transtibial amputees. Gait Posture. 2009; 30(3):356-363. 
  2. Bellmann M, Schmalz T, Ludwigs E, Blumentritt S. Immediate effects of a new microprocessor-controlled prosthetic knee joint: a comparative biomechanical evaluation. Arch Phys Med Rehabil. 2012; 93(3):541-549.
  3. Burnfield JM, Eberly VJ, Gronely JK, et al. Impact of stance phase microprocessor-controlled knee prosthesis on ramp negotiation and community walking function in K2 level transfemoral amputees. Prosthet Orthot Int. 2012; 36(1):95-104.
  4. Chin T, Machida K, Sawamura S, et al.  Comparison of different microprocessor controlled knee joints on the energy consumption during walking in trans-femoral amputees: intelligent knee prosthesis (IP) versus C-leg.  Prosthet Orthot Int. 2006; 30(1):73-80.
  5. Chin T, Sawamura S, Shiba R, et al. Effect of an Intelligent Prosthesis (IP) on the walking ability of young transfemoral amputees: comparison of IP users with able-bodied people. Am J Phys Med Rehabil. 2003; 82(6):447-451.
  6. Darter BJ, Wilken JM. Energetic consequences of using a prosthesis with adaptive ankle motion during slope walking in persons with a transtibial amputation. Prosthet Orthot Int. 2014; 38(1):5-11.
  7. Datta D, Heller B, Howitt J. A comparative evaluation of oxygen consumption and gait pattern in amputees using Intelligent Prostheses and conventionally damped knee swing-phase control. Clin Rehabil. 2005; 19(4):398-403.
  8. Eberly VJ, Mulroy SJ, Gronley JK, et al. Impact of a stance phase microprocessor-controlled knee prosthesis on level walking in lower functioning individuals with a transfemoral amputation. Prosthet Orthot Int. 2013 Oct 17. [Epub ahead of print]
  9. Fradet L, Alimusaj M, Braatz F, Wolf SI. Biomechanical analysis of ramp ambulation of transtibial amputees with an adaptive ankle foot system. Gait Posture. 2010; 32(2):191-198.
  10. Hafner BJ, Willingham LL, Buell NC, et al. Evaluation of function, performance, and preference as transfemoral amputees transition from mechanical to microprocessor control of the prosthetic knee.  Arch Phys Med Rehabil. 2007; 88(2):207-217.
  11. Herr HM, Grabowski AM. Bionic ankle-foot prosthesis normalizes walking gait for persons with leg amputation. Proc Biol Sci. 2012; 279(1728):457-464.
  12. Highsmith MJ, Kahle JT, Shepard NT, Kaufman KR. The effect of the C-Leg knee prosthesis on sensory dependency and falls during sensory organization testing. Technol Innov. 2014; 2013(4):343-347.
  13. Johansson JL, Sherrill DM, Riley PO, et al.  A clinical comparison of variable-damping and mechanically passive prosthetic knee devices.  Am J Phys Med Rehabil. 2005; 84(8):563-575.
  14. Kahle JT, Highsmith MJ, Hubbard SL. Comparison of nonmicroprocessor knee mechanism versus C-Leg on Prosthesis Evaluation Questionnaire, stumbles, falls, walking tests, stair descent, and knee preference. J Rehabil Res Dev. 2008; 45(1):1-14.
  15. Kaufman KR, Levine JA, Brey RH, et al. Energy expenditure and activity of transfemoral amputees using mechanical and microprocessor-controlled prosthetic knees. Arch Phys Med Rehabil. 2008; 89(7):1380-1385.
  16. Kaufman KR, Levine JA, Brey RH, et al. Gait and balance of transfemoral amputees using passive mechanical and microprocessor-controlled prosthetic knees. Gait Posture. 2007; 26(4):489-493.
  17. Klute GK, Berge JS, Orendurff MS, et al.  Prosthetic intervention effects on activity of lower-extremity amputees. Arch Phys Med Rehabil. 2006; 87(5):717-722. 
  18. Orendurff MS, Segal AD, Klute GK, et al. Gait efficiency using the C-leg. J Rehabil Res Dev. 2006; 43(2):239-246.
  19. Schmalz T, Blumentritt S, Jarasch R. Energy expenditure and biomechanical characteristics of lower limb amputee gait: the influence of prosthetic alignment and different prosthetic components. Gait Posture. 2002; 16(3):255-263.  
  20. Segal AD, Orendurff MS, Klute GK, et al. Kinematic and kinetic comparisons of transfemoral amputee gait using C-Leg and Mauch SNS prosthetic knees. J Rehabil Res Dev. 2006; 43(7):857-870. 
  21. Seymour R, Engbretson B, Kott K, et al. Comparison between the C-leg microprocessor-controlled prosthetic knee and non-microprocessor control prosthetic knees: a preliminary study of energy expenditure, obstacle course performance, and quality of life survey. Prosthet Orthot Int. 2007; 31(1):51-61. 
  22. Taylor MB, Clark E, Offord EA, Baxter C. A comparison of energy expenditure by a high level trans-femoral amputee using the Intelligent Prosthesis and conventionally damped prosthetic limbs. Prosthet Orthot Int. 1996; 20(2):116-121.
  23. Theeven PJ, Hemmen B, Brink PR, et al. Measures and procedures utilized to determine the added value of microprocessor-controlled prosthetic knee joints: a systematic review. BMC Musculoskelet Disord. 2013; 14: 333.
  24. Theeven P, Hemmen B, Rings F, et al. Functional added value of microprocessor-controlled knee joints in daily life performance of Medicare Functional Classification Level-2 amputees. J Rehabil Med. 2011; 43(10):906-915.
  25. Williams RM, Turner AP, Orendurff M, et al.  Does having a computerized prosthetic knee influence cognitive performance during amputee walking? Arch Phys Med Rehabil. 2006; 87(7):989-994.
  26. Wolf SI, Alimusaj M, Fradet L, et al. Pressure characteristics at the stump/socket interface in transtibial amputees using an adaptive prosthetic foot. Clin Biomech (Bristol, Avon). 2009; 24(10):860-865.    

Government Agency, Medical Society, and Other Authoritative Publications:

  1. California Technology Assessment Forum (CTAF). Microprocessor-controlled prosthetic knees. A Technology Assessment. San Francisco, CA: CTAF; October, 2007. Available at: Accessed on August 22, 2014.
  2. Washington State Health Care Authority, Health Technology Assessment Program. Microprocessor-controlled lower limb prosthetics. October 12, 2011. Available at: Accessed on August 22, 2014. 

Above Knee Prosthetics
Adaptive Prosthesis
C-Leg® Compact
Endolite® Smart Adaptive knee
Ossur Power Knee™
Otto-Bock C-Leg® Compact
Seattle Limb Systems Power Knee®
Trulife Power Knee®

The use of specific product names is illustrative only.  It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.

Document History
Reviewed11/13/2014Medical Policy & Technology Assessment Committee (MPTAC) review. No change to position statement.  Updated Rationale and Reference sections.
Reviewed11/14/2013MPTAC review. No change to position statement.  Updated Coding section with 01/01/2014 HCPCS changes.
Reviewed11/08/2012MPTAC review. No change to position statement. Updated Rationale, Reference and Index sections.  Updated Coding section with 01/01/2013 HCPCS changes.
Reviewed11/17/2011MPTAC review. Added the Genium™ Bionic Prosthetic System to existing medically necessary statement addressing microprocessor controlled lower limb prosthesis. Added PowerFoot BiOM device to existing investigational and not medically necessary statement addressing microprocessor controlled foot-ankle prosthesis.  Updated Rationale, Background, and Reference and Index sections.
Reviewed02/17/2011MPTAC review.  No change to position statement. Updated Index section.
Revised02/25/2010MPTAC review. Added microprocessor controlled foot-ankle prosthesis (e.g., Proprio Foot) as investigational and not medically necessary for all indications. Updated Coding, Rationale and Reference sections.
Revised02/26/2009MPTAC review. Added medically necessary position and criteria for microprocessor controlled lower limbs. Updated Rationale, Coding and Reference sections.
Revised08/28/2008MPTAC review. Changed position statement from Investigational and Not Medically Necessary to Not Medically Necessary.  Updated Rationale, Coding and Reference sections.
Reviewed05/15/2008MPTAC review. No change to position statement. Updated Rationale and Reference sections
 02/21/2008The phrase "investigational/not medically necessary" was clarified to read "investigational and not medically necessary." This change was approved at the November 29, 2007 MPTAC meeting.
Reviewed05/17/2007MPTAC review. No change to position statement. Updated Rationale and Reference sections.  Coding updated; removed HCPCS L5846 and L5847 deleted 12/31/2004, and K0670 deleted 12/31/2005.
Reviewed06/08/2006MPTAC review. No change to position; updated references. 
 01/01/2006Updated Coding section with 01/01/2006 CPT/HCPCS changes
Revised07/14/2005MPTAC review. Revision based on Pre-merger Anthem and Pre-merger WellPoint Harmonization.
Pre-Merger OrganizationsLast Review DateDocument NumberTitle
Anthem, Inc.09/19/2003OR-PR.00003Computerized Limbs
WellPoint Health Networks, Inc.06/24/20049.01.07Microprocessor Controlled Lower Limb Prosthesis (Above Knee Prosthetics)