BlueCross and BlueShield of Montana Medical Policy/Codes
Lower Limb Prosthetics, Including Microprocessor Prosthetics
Chapter: Durable Medical Equipment
Current Effective Date: February 01, 2014
Original Effective Date: July 18, 2013
Publish Date: January 15, 2014
Revised Dates: January 15, 2014

Amputated and/or missing limbs result from accidents, disease, and congenital disorders. A lower limb prosthetic is a device or artificial substitute designed to replace the function and/or appearance of the absent limb.

The patient’s condition is an important factor to consider in choosing a prosthesis. To be functionally successful with a prosthesis, the patient must demonstrate sufficient trunk control, good upper body strength, static and dynamic balance, and adequate posture. The basic goals with prosthetic use are stability, ease of movement, energy efficiency, and appearance of a natural gait. The prescription for a prosthesis depends on the activity level and specific needs of each individual patient. Clinical assessment of the patient’s rehabilitation potential should be based on the following functional levels:

Level 0:    Does not have the ability or potential to ambulate or transfer safely with or without assistance and a prosthesis does not enhance his/her quality of life or mobility.

Level 1:    Has the ability or potential to use a prosthesis for transfers or ambulating on level surfaces at fixed cadence; typical of the limited and unlimited household ambulator.

Level 2:    Has the ability or potential for ambulating with the ability to traverse environmental barriers such as curbs, stairs, or uneven surfaces; typical of the limited community ambulator.

Level 3:    Has the ability or potential for ambulating with variable cadence; typical of the community ambulator who has the ability to traverse most environmental barriers and may have vocational, therapeutic, or exercise activity that demands prosthetic utilization beyond simple locomotion.

Level 4:    Has the ability or potential for prosthetic ambulating that exceeds basic ambulating skills, exhibiting high impact, stress, or energy levels; typical of the prosthetic demands of the child, active adult, or athlete.

Generally, the earlier a prosthesis is fitted, the better it is for the amputee. Early ambulation helps keep the patient active, accelerates stump shrinkage, helps prevent flexion contractures, and can reduce phantom limb pain. Immediate postsurgical or early fitting procedures are typically performed in the hospital setting immediately after surgery. These procedures include specific dressings and fittings that are intended to prepare the residual limb for a prosthesis. An initial (preparatory) prosthesis and/or immediate postoperative prosthesis (IPOP) may be used to accelerate the rehabilitation process. It is intended to be temporary for several weeks or months until the stump stabilizes and a permanent (definitive) prosthesis is fitted. The base initial and preparatory prostheses include the necessary elements, and usually additions and/or substitutions are not required. However, many physicians prefer to postpone prosthetic intervention until the wound is healed. If necessary, a patient can be fitted for a definitive prosthesis without ever having a preparatory prosthesis. In this case, the socket fitting should be delayed until the residual limb is fully mature (usually 3-4 months) or until the patient’s weight and stump circumference have stabilized.

There is no precise prescription for lower limb prostheses as fitting a prosthesis is very individualized to each patient. A poorly designed or badly fitted prosthesis can be as disabling as the actual amputation. A  prosthesis with components that are appropriate for functional level and physical condition helps the patient avoid future medical problems and injury to the residual limb.

Amputation level is a factor to consider in choosing a prosthesis. The following list identifies the base prosthesis for different levels of amputation:

  • Partial foot prosthesis (PFP)—for absence of the foot and/or toes below the ankle.
  • Ankle (Syme's) Prosthesis (SP)—for absence of the foot and ankle just above the ankle joint.
  • Below Knee Prosthesis (BKP)—for absence of the foot and ankle below the knee joint.
  • Above Knee Prosthesis (AKP)—for absence of the foot, ankle, shin and thigh above the knee joint.
  • Knee Disarticulation Prosthesis (KDP)—for absence of the foot, ankle and shin at the knee joint level.
  • Hip Disarticulation Prosthesis (HDP)—for absence of the complete leg including the foot, ankle, shin and thigh at the hip joint level.
  • Hemipelvectomy Prosthesis (HP)—for absence of the complete leg including the foot, ankle, shin, thigh, hip and pelvis.

A lower limb prosthesis is made up of a base prosthesis combined with the possible addition of any of the following components: 

  • Socket;
  • Prosthetic sock or liner;
  • Socket inserts;
  • Pylon, or knee-shin system;
  • Articulating joint;
  • Suspension system;
  • Protective outer covering;
  • Foot, ankle, or foot-ankle system.

Each additional or “add-on” component requires justification with regard to medical necessity related to activities of daily living.

The socket is the basis for the connection between the patient and the prosthesis, and a good fit is extremely important to the success of the prosthesis. The most common socket for the BKP is a Patellar-Tendon-Bearing (PTB) design. With an AKP, the transected femur can support very little weight at its end, so the socket is designed to shift the weight onto the side of the thigh and the pelvis. The quadrilateral socket has a contoured area called the ischial seat that supports the ischium (part of the hip bone). The ischial containment socket is made of more flexible materials, and encapsulates the ischium in a way that provides more stability and control. Sockets can be flexible, expandable, or rigid, and are made of a variety of materials including wood, leather, polyester, acrylic, carbon, plastic, or a combination of these. For example, a rigid carbon frame over a flexible inner socket offers strength and stability with flexibility and comfort.

Prosthetic socks provide comfort and ventilation, and help prevent skin abrasion. They should be changed and laundered daily to reduce skin irritation and dermatitis. Prosthetic liners and socket inserts are made of soft material or gel that is molded to the residual limb and acts as an interface between the hard weight-bearing socket and the skin. The suspension system attaches the prosthesis to the residual limb. This system can be a variety of belts, wedges, straps, suction, inserts, or some combination of these. 

Knee-shin systems can be exoskeletal (crustacean) or endoskeletal. The exoskeletal knee-shin system is a one-piece design that entails wood or foam enclosed by a hard plastic finish, usually shaped like a leg, and without interchangeable parts. This type of knee-shin system is very durable and simple. Because it is sturdy and heavy duty, it may be preferred by people who will be in harsh environments, such as farmers or other outdoor workers. Endoskeletal knee-shin systems are more complex and have interchangeable parts under a soft outer cover. Endoskeletal systems are lightweight and have many different component options, such as different knee units that can be introduced as the patient’s functional needs change. 

Prosthetic Knee

The knee joint has three functions: provide support during stance phase of ambulation, produce smooth control during swing phase, and maintain unrestricted motion for sitting and kneeling. More than 100 different prosthetic knee and ankle/foot designs are currently available. The choice of the most appropriate design may depend on the patient’s underlying activity level. For example, the requirements of a prosthetic knee in an elderly, largely homebound individual will be quite different than a younger, active person. In general, key elements of a prosthetic knee design involve providing stability during both the stance phase and swing phase of the gait. Prosthetic knees also vary in their ability to alter the cadence of the gait, or the ability to walk on rough or uneven surfaces. In contrast to more simple prostheses, which are designed to function optimally at one walking cadence, fluid and hydraulic-controlled devices are designed to allow amputees to vary their walking speed by matching the movement of the shin portion of the prosthesis to the movement the upper leg. For example, the rate at which the knee flexes after “toe-off” and then extends before heel strike depends in part on the mechanical characteristics of the prosthetic knee joint. If the resistance to flexion and extension of the joint does not vary with gait speed, the prosthetic knee extends too quickly or too slowly relative to the heel strike when the cadence is altered. When properly controlled, hydraulic or pneumatic swing-phase controls allow the prosthetist to set a pace that is adjusted to the individual amputee from a very slow pace to a race-walking pace. Hydraulic prostheses are heavier than other options and require gait training; for these reasons, these prostheses are generally prescribed for athletic or fit individuals. Other design features include multiple centers of rotation, referred to as “polycentric knees.” The mechanical complexity of these devices allows engineers to optimize selected stance and swing-phase features. The following are prosthetic knee options:

  • Manual locking knee is a very stable knee that is locked during gait. The patient releases the lock mechanism manually to sit down. This knee may be used for patients who have very short residual limb and/or poor hip strength and are unable to control the knee.
  • Single-axis constant friction knee has a simple hinge and single pivot point. These knees are set to walk at one speed, and do not have stance control.
  • Weight-activated stance control knee is a single-axis constant friction knee with a braking mechanism. When the patient puts his weight on the knee during gait, a braking mechanism is applied and the knee won’t buckle.
  • Polycentric knees, also referred to as 4-bar knees, have multiple centers of rotation allowing for stability at all phases of gait. The 4-bar linkage allows the knee to collapse better during the swing phase and to bend easier for sitting. These can incorporate a hydraulic or pneumatic unit to permit variable walking speeds.
  • Pneumatic or hydraulic knees have pistons inside cylinders containing air (pneumatic) or fluid (hydraulic); these units adjust gradually to changes in gait speed, which allows walking at variable speeds and permits a somewhat more natural gait.
  • Microprocessor-controlled prosthetic knees have been developed, including the Intelligent Prosthesis (Blatchford, U.K.), the Adaptive (Endolite, England), the Rheo (Ossur, Iceland), and the C-Leg (Otto Bock Orthopedic Industry, Minneapolis, MN). These devices are equipped with a sensor that detects when the knee is in full extension and adjusts the swing phase automatically, permitting a more natural walking pattern of varying speeds. For example, the prosthetist can specify several different optimal adjustments that the computer later selects and applies according to the pace of ambulation. In addition, many of these devices use microprocessor control in both the swing and stance phases of gait. By improving stance control, they may provide increased safety, stability, and function; for example, the sensors are designed to recognize a stumble and stiffen the knee, thus avoiding a fall. Other potential benefits of microprocessor-controlled knee prostheses are improved ability to navigate stairs, slopes, and uneven terrain, and reduction in energy expenditure and concentration required for ambulation.
    • The C-Leg was cleared for marketing in 1999 through the 510(k) process of the U.S. Food and Drug Administration (FDA, K991590). The C-Leg is versatile, controls both stance and swing, performs better on stairs, and must be combined with one of five specific foot devices.
    • The Rheo Knee is very comparable to the C-Leg, and can be combined with any foot device.
    • The Adaptive Knee also has both swing and stance control, but because it is lightweight, durable, and has more emphasis on swing than stance, this knee is well-suited to patients who are very strong and active at a higher functional level.
    • Otto Bock’s Compact is designed for stability in stance phase, and does not have swing microprocessors. This knee would be a good choice for an appropriately active patient with focus on stability, where gait speed is not as important an issue. 
    • Knees with processors for swing-only have a lesser degree of stance control, and are considered a clinical option when the patient has a higher activity level combined with a very high residual limb control; examples include the DAW, Intelligent Knee, IP+, Smart IP, and Seattle Power Knee.

Prosthetic Ankle/Foot

The basic functions of the prosthetic foot are to provide a stable weight bearing and shock absorbing surface, to replace lost muscle function, and to replicate the anatomic joint. Conventional prosthetic feet can be basic (non-articulated, unmoving), articulated or dynamic-response (energy-storing). Articulated feet have one or more joints. The single-axis foot has one joint, and can be used to help keep the knee stable. The multi-axis foot has motion about all three axes of the ankle and is good for walking on uneven surfaces. The multi-axis and dynamic-response feet are energy-storing feet. An energy-storing foot is capable of absorbing energy in a flexible keel (horizontal device in the foot) during the roll-over part of the stance phase of gait. The keel then springs back to provide push-off assistance to get the toe off the ground to start the swing phase. The simplest type of non-articulated foot is the SACH (solid ankle-cushion heel) foot, which has a rigid keel, and a soft rubber heel that provides ankle action. The SAFE (solid ankle-flexible-endoskeletal) foot has the same action as the SACH plus the sole is able to conform to irregular surfaces, which makes it easier to walk on uneven terrain. The SAFE foot is also called a “flexible keel foot”. The SACH and SAFE feet are non-energy-storing feet.

Microprocessor-controlled ankle-foot prostheses are being developed for transtibial amputees. These include the Proprio Foot (Ossur) and the iPED (developed by Martin Bionics LLC and licensed to College Park Industries). With sensors in the feet that determine the direction and speed of the foot’s movement, a microprocessor controls the flexion angle of the ankle, allowing the foot to lift during the swing phase and potentially adjust to changes in force, speed, and terrain during the step phase. The intent of the technology is to make ambulation more efficient and prevent falls in patients ranging from the young active amputee to the elderly diabetic patient. The Proprio Foot is the only microprocessor-controlled foot prosthesis that is commercially available at this time and is a class-I device that is exempt from 510(k) marketing clearance. The manufacturer must register the prosthesis with the restorative devices branch of the FDA and keep a record of any complaints but does not have to undergo a full review. Information on the Ossur website indicates use of the Proprio Foot for low- to moderate- impact for transtibial amputees who are classified as level K3 (i.e., community ambulatory, with the ability or potential for ambulation with variable cadence). According to Ossur, the Proprio Foot is the first and only microprocessor foot to utilize the power of artificial intelligence with Terrain Logic™ software. In just 15 steps, individual style of walking is traced and recorded as a “gait profile”. The customized “gait profile” is then automatically launched each time a step is taken. Terrain Logic™ software instantly adjusts and moves the foot when surfaces change. Amputees can quickly negotiate unexpected terrain without the risk of stumbling or falling. According to Ossur, the Proprio Foot ensures safety and stability by doing the following:

  • Detects when the toe leaves the ground and lifts it, thereby resulting in the safe clearance of curbs and other irregularities in terrain.
  • Positions the foot up or down to create natural function when sitting or standing.
  • Places the foot solidly on steps and uneven ground to enhance stability and balance. Calibrated alignment control helps prevent premature knee flexion and knee hyperextension.

Microprocessor-Controlled Foot, Powered Foot and Knee, and New Generation Microprocessor Knee

In development are lower-limb prostheses that also replace muscle activity in order to bend and straighten the prosthetic joint. For example, the Power Foot (developed at the Massachusetts Institute of Technology and licensed to iWalk) is a myoelectric prosthesis for transtibial amputees that uses muscle activity from the remaining limb for the control of ankle movement. This prosthesis is designed to propel the foot forward as it pushes off the ground during the gait cycle, which in addition to improving efficiency, has the potential to reduce hip and back problems arising from an unnatural gait with use of a passive prosthesis. This technology is limited by the size and the weight required for a motor and batteries in the prosthesis. The Power Knee (Ossur), which is designed to replace muscle activity of the quadriceps, uses artificial proprioception with sensors similar to the Proprio Foot in order to anticipate and respond with the appropriate movement required for the next step. The Power Knee is currently in the initial launch phase in the United States. The Genium™ Bionic Prosthetic System is a new generation of microprocessor-controlled, intelligent knee prostheses. The Genium uses software with a complex sensory system, including a gyroscope and an accelerometer, creating a natural, intuitive gait. It is designed to anticipate the user’s movement, not just respond to them, with both swing and stance control predicted by multi-modal propriceptive input. The Endolite Êlan foot is another promising foot/ankle system with microprocessor controlled speed and terrain response. The Êlan has sensors that continuously monitor environmental feedback and an algorithm that changes the foot characteristic to provide safety, comfort and energy efficiency on flat ground, and descending or ascending ramps and stairs. (47)

Hydraulic Prosthetic Hip

Fitting and wearing hip disarticulation prostheses presents several challenges, including poor gait pattern, socket discomfort, instability, loss of mobility, prosthesis weight and energy expenditure. The Canadian hip disarticulation prosthesis was developed by McLaurin more than 50 years ago, and is the “standard” hip disarticulation prosthesis. These prostheses move in a single plane, and require locking of the knee and hip for walking and unlocking to sit down. A new prosthetic hip joint, the Helix3DHip® (OttoBock), consists of a four-axis mechanism with hydraulic stance and swing-through phase control, which is reported to have the advantages of greater support and stability, and three-dimensional movement similar to the ball joint of the natural hip, and more controlled heel strike.


Each benefit plan, summary plan description or contract defines which services are covered, which services are excluded, and which services are subject to dollar caps or other limitations, conditions or exclusions. Members and their providers have the responsibility for consulting the member's benefit plan, summary plan description or contract to determine if there are any exclusions or other benefit limitations applicable to this service or supply.  If there is a discrepancy between a Medical Policy and a member's benefit plan, summary plan description or contract, the benefit plan, summary plan description or contract will govern.



Preparatory, initial, permanent, and definitive lower limb prostheses may be considered medically necessary when the patient:

  • is at functional Level 1-4 (defined in Description section) OR can be expected to reach Level 1-4 within a reasonable period of time; AND
  • meets functional level criteria for prosthetic components (additions, substitutions, and/or replacements) as defined below in Tables I, II, and/or III; AND
  • is motivated to ambulate; AND
  • has received a physician prescription for the prosthesis as a result of a recent physician evaluation.

NOTE:  Medical records should document the patient’s current functional capabilities and expected functional potential, including an explanation for any difference.

If the patient has Functional Level 0 (defined in Description section), lower limb prostheses are considered not medically necessary.


Microprocessor knees that have stance-phase or swing-and-stance phase microprocessors may be considered medically necessary for only those patients who meet ALL of the following criteria:

  • Patient is an appropriately active community ambulator, AND
  • Patient has undergone extensive evaluation using the Hanger Prosthetics & Orthotics Patient Assessment Validation Evaluation Tool (PAVET Evaluation for Microprocessor Knee form, which is available on the Blue Cross Blue Shield web site—see **NOTE below Table I), AND
  • Patient’s PAVET scores are between 40-72, as detailed in TABLE I:






Overall score 40-49

Microprocessor for stance phase only may be considered medically necessary (e.g., Otto Bock Compact™)

Overall score of 50-59, AND Cadence score* 14 and below

Microprocessor for stance phase only may be considered medically necessary (e.g., Otto Bock Compact)


Overall score of 50-59, AND Cadence score* 15 and above

Microprocessor for swing-and-stance phase may be considered medically necessary  (e.g., Otto Bock C-Leg™, Ossur Rheo™)

Overall score of 60-72

Microprocessor for swing-and-stance phase may be considered medically necessary  (e.g., Otto Bock C-Leg, Ossur Rheo, Endolite Adaptive™)

* NOTE:  Cadence score is determined by the total of PAVET questions #1, #2, #7, #14, and #15

** NOTE:  To obtain the PAVET.2 Evaluation for Microprocessor Knee form, go to the Provider / Forms page at

Microprocessor knee is considered not medically necessary for the following patients:

  • Those who have a PAVET score less than 40, or
  • Those who have a PAVET score 73 or greater as this high is unrealistic and indicates possible scoring discrepancy. (These patients should be re-evaluated.), or
  • Those who do not meet all of the above criteria.

Microprocessor knees that have only swing-phase microprocessors are considered not medically necessary including, but not limited to, Endolite IP+™, Endolite Smart IP™, Intelligent Knee™, Seattle Power Knee™, and DAW®.

The Genium™ Bionic Prosthetic System microprocessor knee is considered experimental, investigational and/or unproven.

A powered knee is considered experimental, investigational and/or unproven, including but not limited to the Power Knee® (Ossur).

The lithium ion battery for the microprocessor knee is included with the knee, and is repaired or replaced by the manufacturer when needed. Repair or replacement of the battery is covered under the manufacturer’s warranty. When the manufacturer’s warranty has expired, necessary repair or replacement of the lithium ion battery is considered medically necessary. Spare or extra batteries are considered not medically necessary, as they are convenience items.

One (1) lithium ion battery charger is considered medically necessary for each microprocessor knee. More than one (1) battery charger is considered not medically necessary.


A four-axis, hydraulic or pneumatic hip joint (e.g., Helix3DHip® [OttoBock]) may be considered medically necessary when the patient has an overall score of 50 or higher, AND Cadence score* 15 or higher on the PAVET Evaluation, and the Helix3DHip will be used in conjunction with the OttoBock C-Leg.


Microprocessor-controlled or powered ankle/foot is considered experimental, investigational, and/or unproven including, but not limited to, Proprio Foot® (Ossur), iPED® (Martin Bionics), PowerFoot BiOM® (iWalk), and Êlan® (Endolite).

PROSTHETIC COMPONENTS (i.e., additions, substitutions, replacements, and/or modifications)

Additions, substitutions, replacements, and/or modifications to lower limb prostheses (except microprocessor-controlled prosthetic knees) may be considered medically necessary based on the patient’s potential functional abilities (see Table II below).

EXCEPTION:  Certain additions and substitutions to initial or preparatory prostheses are considered not medically necessary as detailed in Table III below, because initial/preparatory prostheses are temporary and include the necessary elements.

NOTE:  Functional levels are defined in Description Section below.



Additions, substitutions and/or replacements that may be considered medically necessary for permanent/definitive prosthesis, based on functional level:





KNEES (Except microprocessor knees)

  • 4-Bar knee, friction control
  • Universal multiplex, friction control
  • 4-Bar knee, friction control
  • Universal multiplex, friction control
  • Pneumatic and hydraulic knees
  • 4-Bar knee, friction control
  • Universal multiplex, friction control


  • Exoskeletal knee-shin systems
  • Endoskeletal knee-shin systems
  • Exoskeletal knee-shin systems
  • Endoskeletal knee-shin systems
  • Exoskeletal knee-shin systems
  • Endoskeletal knee-shin systems


Axial rotation unit

Axial rotation unit

Axial rotation unit


  • External keel SACH foot
  • Single-axis ankle/foot
  • Flexible-keel foot
  • Multi-axial ankle/foot
  • External keel SACH foot
  • Single-axis ankle/foot
  • Flex foot system
  • Energy-storing foot
  • Multiaxial ankle/foot, dynamic response
  • Flex walk system or equal
  • Shank foot system with vertical loading pylon
  • Flexible-keel foot
  • Multi-axial ankle/foot
  • External keel SACH foot
  • Single-axis ankle/foot



1.  Two test (diagnostic) sockets may be considered medically necessary for an individual prosthesis. More than two require documentation of medical necessity.

2.  Socket replacements may be considered medically necessary with documentation of functional and/or physiological need. Examples include, but are not limited to:

  • Changes in residual limb,
  • Functional need changes.





These additions, substitutions and/or replacements are not covered as they ARE CONSIDERED NOT MEDICALLY NECESSARY:


  • Acrylic socket; leather socket; wood socket; air, fluid, or gel cushion socket; suction socket;
  • Protective covering;
  • Ultra-lightweight exoskeletal system;
  • Flex foot system.


  • Test socket , acrylic socket; flexible inner socket; air, fluid, or gel cushion socket;
  • Protective outer covering;
  • Molded supracondylar suspension (PTS or similar);
  • Single-axis knee joints.


  • Acrylic socket; leather socket; wood socket; air, fluid, or gel cushion socket;
  • Protective outer covering;
  • Exoskeletal knee-shin system;
  • Endoskeletal hydracadence system;
  • Ultra-lightweight exoskeletal system;
  • Flex foot system.


  • Test socket , acrylic socket ; air, fluid, or gel cushion socket; flexible inner socket; suction suspension, socket;
  • Protective outer covering;

NOTE:  Determination of coverage for selected prostheses and components with respect to potential functional levels represents the usual case.  Exceptions will be considered in an individual case if additional documentation is provided that justifies the medical necessity.


Prosthetic socks and harnesses may be considered medically necessary when essential to the use of the prosthesis.

More than two of the same socket inserts per individual prosthesis at the same time are considered not medically necessary.

When immediate postsurgical or early fitting procedures are provided, test (diagnostic) sockets are considered not medically necessary as test sockets cannot be used with these procedures.

Policy Guidelines

Generally, coverage will include supplies necessary for effective use of a covered prosthesis, as well as adjustments, repairs, and replacements that are necessary to make the equipment functional for as long as the equipment continues to be medically necessary.

Shoes (a pair) may be covered when one or both shoes are an integral part of the artificial limb(s). Check the member’s contract.

HCPCS codes:

L5856  Swing and stance phase microprocessor knees

L5857  Swing phase only microprocessor knees

L5858  Stance phase only microprocessor knees

L5961  Hydraulic/pneumatic hip (e.g., Helix Hip Joint)

L5973  Microprocessor ankle/foot


Lower limb amputation is a life-altering event that impacts most activities, including employment, personal relationships, recreation, activities of daily living and self-care. Some determinants of a successful outcome with prosthetic use include comfortable to wear, easy to apply and remove, durable, good mechanical function and reasonably low maintenance. To be functionally successful with a lower limb prosthesis, the patient should demonstrate sufficient trunk control, good upper body strength, static and dynamic balance, and adequate posture. Stability, ease of movement, energy efficiency, and appearance of a natural gait are key elements to achieve with prosthetic use. Some of the challenges faced by prosthetic wearers include changing rate of speed, maneuvering steps, inclines and uneven terrain, fear of falling and avoidance of activity that could cause falls.

Most recently, microprocessor-controlled prosthetic knees have become available. In evaluating microprocessor-controlled knee prostheses, relevant outcomes may include the patient’s perceptions of subjective improvement attributable to the prosthesis and level of activity and/or function. In addition, the energy costs of walking or gait analysis may be a more objective measure of the clinical benefit of the microprocessor-controlled prosthetic knee.

Published data on the microprocessor-controlled knee prostheses are minimal; the bulk of the literature focuses on the Intelligent Prosthesis (IP), which is similar to the C-Leg. Kirker and colleagues (1) reported on the gait symmetry, energy expenditure, and subjective impression of the IP in 16 patients with an above knee amputation related to trauma or congenital anomaly. The patients had previously functioned adequately with a pneumatic swing phase control unit and were offered a trial of an IP. At the beginning of the study the patients had been using the IP for one to nine months. The patients responded to a questionnaire using a visual analog scale regarding how much effort was needed to walk at their normal, faster, and slower speeds on smooth level surfaces, outdoors or at work, up and down a slope, and up and down steps. The patients also indicated their overall preference for one or the other. Subjects reported that significantly less effort was required when using the IP prosthesis to walk at normal or high speeds, but there was no difference for a slow gait. Effort was reduced walking outdoors or at work. Subjects reported a strong preference for the IP versus the standard pneumatic leg.

Datta and Howitt (3) reported on the results of a questionnaire survey of 22 amputees who were switched from pneumatic swing phase control prostheses to an IP device. All patients were otherwise fit and fairly active. The questionnaire focused on functional attributes of the two prostheses, such as speed of walking, and walking up and down stairs, energy levels, and naturalness of the gait. All subjects reported that the IP was an improvement over the conventional prosthesis. The main benefits suggested by this subjective study were the ability to walk at various speeds, reduction of effort of walking, and patients' perception of improvement of walking pattern.

In 2000, the Veteran’s Administration Technology Assessment Program issued a “short report” on computerized lower limb prostheses that considered the same data as referenced above, and offered the following observations and conclusions (6):

  • Energy requirements of ambulation (compared to requirements with conventional prostheses) are decreased at walking speeds slower or faster than the amputee’s customary speed, but are not significantly different at customary speeds.
  • Results on the potentially improved ability to negotiate uneven terrain, stairs, or inclines are mixed. Such benefits, however, could be particularly important to meeting existing deficit in the reintegration of amputees to normal living, particularly those related to decreased recreation opportunities.
  • Users’ perceptions of the microprocessor-controlled prosthesis are favorable. Where such decisions are recorded or reported, the vast majority of study participants choose not to return to their conventional prosthesis or keep these only as back-up to acute problems with the computerized one.
  • Users’ perceptions may be particularly important for evaluating a lower limb prosthesis, given the magnitude of the loss involved, along with the associated difficulty of designing and collecting objective measures of recovery or rehabilitation. However resilient the human organism or psyche, loss of a limb is unlikely to be fully compensated. A difference between prostheses that is sufficient to be perceived as distinctly positive to the amputee may represent the difference between coping and a level of function recognizable closer to the preamputation level.
  • Mechanical failure is recorded in some of the studies, but seems to be rare. The manufacturer indicates that some C-Leg™ devices have been used for extended periods (up to 5 years) without mechanical or electrical problems.
  • The UK Medical Devices Agency has conducted an evaluation of the Endolite Intelligent Prosthesis, with generally favorable results. Recognizing constraints related to the substantial cost of the prosthesis, the UK National Health Service makes it available to a wide range of patients, and has arranged with the manufacturer for a program to lend critical components, should these components of the prosthesis require factory repair.

Assessing and improving mobility are among the primary goals of rehabilitation for lower-limb amputees, who face the additional challenge of relearning ambulatory skills. Specific challenges include absence of feedback from the foot or leg, changes in lower body weight distribution, and mechanical difficulties in coordinating the movement of the prosthesis with the intact limbs. The transfemoral amputee lacks feedback from the knee joint that normally determines a great deal of stability, as well as limb progression in the gait cycle.

Risk factors for falling include age, chronic disease, gait and balance instability, decreased vision, altered mental status, and medication use; lower extremity amputees, especially older amputees who have lost their limb as a result of chronic vascular disease, experience at least one or more of these risk factors. The psychological consequences of falling (i.e., fear of falling and lack of balance confidence) can influence performance of activities and result in self-imposed restriction that can lead to deterioration in balance, muscle endurance, strength, flexibility, and coordination, as well as mental depression and other physical manifestations, e.g., muscle insufficiencies, cardiovascular disease, etc. Miller et al. studied the prevalence and risk factors of falling and concluded that falling and fear of falling are pervasive among amputees. In another study, Miller et al. sought to determine if falling, fear of falling, and balance confidence are important factors among amputee patients with respect to three quality of life indicators: mobility capability, mobility performance, and participation in social activities. They concluded that balance confidence was a relevant factor affecting these quality of life indicators. (6, 7, 12)

Microprocessor-controlled knees use onboard computers that can sample real-time data and adjust resistances for a range of speeds at which the patient ambulates, regardless of the alignment. The improved gait symmetry, consistency, and controlled movements in swing and stance build amputees’ confidence in the prosthesis, resulting in better balance confidence and decreased fear of falling.

A MEDLINE literature search was conducted through August 2008. Microprocessor foot/ankle is a fairly new device; no studies or evidence was found that demonstrate that these prostheses provide energy efficiency, better balance or stability, or any other benefit, and there is no protocol for determining who would benefit from these.

2011 Update

A search of peer reviewed literature was performed through June 2011.

Microprocessor and Powered Knee Prostheses

Buckley and colleagues (2) focused on a comparison of the energy cost of an IP with a pneumatic swing-phase control unit in three patients. Two subjects showed a decrease in energy consumption, while a third showed no change. Another study of one patient also reported lower oxygen consumption with an IP prosthesis. Finally, Datta and colleagues (19) studied oxygen consumption at different walking speeds in 10 patients using an IP and a pneumatic swing gait prosthesis. Similar to the Kirker et al. (1) study, the IP was associated with less oxygen consumption at lower walking speeds only. Studies of gait analyses did not identify any other significant differences. Obviously, few conclusions can be drawn from these small trials. Specifically, the clinical significance of decreased oxygen consumption at lower walking speeds is uncertain.

One industry-sponsored study (30) assessed function, performance, and preference for the C-Leg in 21 unilateral transfemoral amputees using an A-B-A-B design. Subjects were fully accustomed to a mechanical knee system (various types) and were required to show proficiency in ambulating on level ground, inclines, stairs, and uneven terrain prior to enrollment. Of the 17 subjects (81%) who completed the study, patient satisfaction was significantly better with the microprocessor-controlled prosthesis as measured by the Prosthesis Evaluation Questionnaire (PEQ). Fourteen preferred the microprocessor-controlled prosthesis, two preferred the mechanical system, and one had no preference. Subjects reported fewer falls, lower frustration with falls, and an improvement in concentration. Objective measurements on the various terrains were less robust, showing improvements only for descent of stairs and hills. Average performance on stair descent improved from a step-to pattern with a rail to a step-over-step with a rail and assistive device. The C-Leg improved hill descent from requiring an assistive device to using a step-to pattern without an assistive device. Unaffected were stair ascent, step frequency, step length, and walking speed. The subjective improvement in concentration was reflected by a small (nonsignificant) increase in walking speed while performing a complex cognitive task (reversing a series of numbers provided by cell phone while walking on a city sidewalk).

All lower-limb amputees returning from Operation Iraqi Freedom and Operation Enduring Freedom currently receive a microprocessor-controlled prosthesis from the Department of Veterans Affairs (VA); 155 veterans were provided with a C-Leg in 2005. A series of papers from the VA reports results from a within-subject comparison of the C-Leg to a hydraulic Mauch SNS knee. Eight (44%) of the 18 functional level 2–3 subjects recruited completed the study; most withdrew due to the time commitment of the study or other medical conditions, two could not be adequately fit, and one could not acclimate to the C-Leg. Of the eight remaining subjects, half showed a substantial decrease in oxygen cost when using the C-Leg, resulting in a marginal improvement in gait efficiency for the group. The improvement in gait efficiency was hypothesized to result in greater ambulation, but a seven-day activity monitoring period in the home/community showed no difference in the number of steps taken per day or the duration of activity. Cognitive performance, assessed by standardized neuropsychological tests while walking a wide hallway in five of the subjects, was not different for semantic or phonemic verbal fluency and not significantly different for working memory when wearing the microprocessor-controlled prosthesis. Although the study lacked sufficient power, results showed a 50% decrease in errors on the working memory task (1.63 vs. 0.88, respectively). Thus, the effect of this device on objective measures of cognitive performance cannot be determined from this study. Subjective assessment revealed a perceived reduction in attention to walking while performing the cognitive test (effect size of 0.79) and a reduction in cognitive burden with the microprocessor-controlled prosthesis (effect size of 0.90). Seven of the eight subjects preferred to keep the microprocessor-controlled prosthesis at the end of the study. The authors noted that without any prompting, all of the subjects had mentioned that stumble recovery was their favorite feature of the C-Leg. (26)

Two small studies of high-functioning amputees (functional level 3–4, n=8 and 10) compared performance with the subject’s own C-Leg to a mechanical model. With little or no acclimation time for the mechanical knee, the studies found that use of the C-Leg resulted in faster time on an obstacle course, a smoother gait, and improved efficiency of hip work. A survey of eight amputees who had previously switched to a C-Leg found that this group of patients felt less fatigued, safer due to a reduced incidence from falls, and more motivated and self-confident when using the C-Leg in comparison with their previous mechanical model. Given the highly selected patient populations and bias in experimental design, the only information provided by these studies is that some current users are satisfied with the microprocessor-controlled knees and that they perform adequately for some people. (26)

Although the literature indicates that microprocessor-controlled knees may perform at least as well as mechanical prostheses, objective evidence of incremental improvement in activities of daily living (e.g., falls and activity levels) is lacking. This may be due, in part, to the individualized prescription of prosthetic components and the difficulty of designing and collecting objective measures of recovery or rehabilitation. The literature does indicate a strong preference for prosthetic knees that control both stance and swing in selected patients. The perceived benefits include an increase in stability, a decrease in falls, and a decrease in the cognitive burden associated with monitoring the prosthesis. As described in the VA short report, “users’ perceptions may be particularly important for evaluating a lower limb prosthesis, given the magnitude of the loss involved…A difference between prostheses sufficient to be perceived as distinctly positive to the amputee may represent the difference between coping and a level of function recognizably closer to the preamputation level.” (6)

As a result of the above studies, it was concluded that a microprocessor-controlled knee may provide incremental benefit for some individuals. Those considered most likely to benefit from these prostheses have both the potential and need for frequent ambulation at variable cadence, on uneven terrain, or on stairs. The potential to achieve a high functional level with a microprocessor-controlled knee includes having the appropriate physical and cognitive ability to be able to use the advanced technology.

Two reports by Kaufman et al. (32, 33) were published describing a within-subject objective comparison of mechanical- and microprocessor-controlled knees in 15 transfemoral amputees (12 men and three women; mean age: 42 years) with a Medicare Classification Level 3 or 4. Following testing with the subject’s usual mechanical prosthesis, the amputees were given an acclimation period of 10 to 39 weeks (average of 18 weeks) with a microprocessor knee before repeat testing. The 2007 report described results from objective balance and gait measurements; measures of energy efficiency and expenditure were reported in 2008. Patients rated the microprocessor knee as better than the mechanical prosthesis in eight of nine categories of the prosthesis evaluation questionnaire. Objective gait measurement included knee flexion and the peak extensor moment during stance measured by a computerized video motion analysis system. Both the extensor moment and knee flexion were significantly different for the two prostheses, indicating a reduction in active contraction of the hip extensors to “pull back” and force the prosthetic knee into extension and resulting in a more natural gait with the microprocessor knee. Balance was improved by approximately 10%, as objectively determined with a computerized dynamic posturography platform. Total daily energy expenditure was assessed over 10 days in free-living conditions. Both daily energy expenditure and the proportion of energy expenditure attributed to physical activity increased. Although the subjects perceived that it was easier to walk with the microprocessor-controlled knee than the mechanical prosthesis, energy efficiency while walking on a treadmill was not significantly different (2.3% change). Taken together, the results indicated that amputees spontaneously increased their daily physical activity outside of the laboratory setting when using a microprocessor knee. These objective assessments support the previously described findings of improved subjective experience with the microprocessor knee.

Hafner and Smith (36) evaluated the impact of the microprocessor-controlled prosthesis on function and safety in level K2 and K3 amputees. The K2 ambulators tended to be older (57 vs. 42 years), but this did not achieve statistical significance in this sample (p=0.05). In this per-protocol analysis, eight level K2 and nine level K3 amputees completed testing with their usual mechanical prosthesis, then with the microprocessor-controlled prosthesis, a second time with their passive prosthesis, and then at 4, 8, and 12 months with the prosthesis that they preferred/used most often. Only subjects who completed testing at least twice with each prosthesis were included in the analysis (four additional subjects did not complete the study due to technical, medical, or personal reasons). Similar to the group’s 2007 report, performance was assessed by questionnaires and functional tasks including hill and stair descent, an attentional demand task, and an obstacle course. Self-reported measures included concentration, multitasking ability, and numbers of stumbles and falls in the previous four weeks. Both level K2 and K3 amputees showed significant improvements in mobility and speed (ranging from 7% to 40%) but little difference in attention with the functional assessments. The self-reported numbers of stumbles and falls in the prior four weeks was found to be lower with the microprocessor-controlled prosthesis. For example, in the level K2 amputees, stumbles decreased from an average of 4.0 to 2.7 per month, semi-controlled falls from 1.6 to 0.6, and uncontrolled (i.e., complete) falls from 0.5 to 0 when using the microprocessor-controlled knee. Re-evaluation of each participant’s classification level at the conclusion of the study showed that 50% of the participants originally considered to be K2 ambulators were now functioning at level K3 (about as many K3 ambulators increased as decreased functional level). These results are consistent with the Veterans Health Administration Prosthetic Clinical Management Program clinical practice recommendations for microprocessor knees, which state that use of microprocessor knees may be indicated for Medicare Level K2 but only if improved stability in stance permits increased independence, less risk of falls, and potential to advance to a less restrictive walking device, and if the patient has cardiovascular reserve, strength, and balance to use the prosthesis. (17)

The Genium has been tested on soldiers returning with battle wounds, and has not been widely tested or used for civilians. A search of peer-reviewed literature did not identify studies that support the use of the Genium knee outside of the research/military setting. In addition, evidence is insufficient to evaluate the health benefits of the powered knee (e.g., Power Knee®). Therefore, these are considered experimental, investigational and/or unproven.

Microprocessor-Controlled and Powered Ankle-Foot Prostheses

A 2008 Cochrane review (40) of ankle-foot prostheses concluded that there was insufficient evidence from high-quality comparative studies for the overall superiority of any individual type of prosthetic ankle-foot mechanism. In addition, the authors noted that the vast majority of clinical studies on human walking have used standardized gait assessment protocols (e.g., treadmills) with limited “ecological validity,” and recommended that for future research, functional outcomes should be assessed for various aspects of mobility such as making transfers, maintaining balance, level walking, stair climbing, negotiating ramps and obstacles, and changes in walking speed.

In 2009, Alimusaj et al. (37) reported gait analysis with the Proprio Foot in 16 transtibial K3-K4 amputees during stair ascent and stair descent. Results with the adaptive ankle (allowing 4 degrees of dorsiflexion) were compared with tests conducted with the same prosthesis but at a fixed neutral angle (similar to other prostheses) and with results from 16 healthy controls. Adaptive dorsiflexion was found to be increased in the gait analysis; however, this had a modest impact on other measures of gait for either the involved or uninvolved limb, with only a “tendency” to be closer to the controls, and the patient’s speed was not improved by the adapted ankle. The authors noted that an adaptation angle of 4 degrees in the stair mode is small compared to physiologic ankle angles, and the lack of power generation with this quasi-passive design may also limit its clinical benefit.

Fradet et al. (41) reported gait analysis with the Proprio Foot in 16 transtibial amputees while walking up and down a ramp. Results with the adaptive mode were compared with the Proprio Foot in a neutral angle and with results from 16 healthy controls. The adapted mode resulted in a more normal gait during ramp ascent, but not during ramp descent. However, some patients reported feeling safer with the plantar flexed ankle (adaptive mode) during ramp descent.

Au and colleagues (38) have reported the design and development of the powered ankle-foot prosthesis; however, clinical evaluation of the prototype was performed in a single patient.  

Evidence is insufficient to evaluate the health benefits of microprocessor-controlled foot prostheses. Therefore, these are considered experimental, investigational and/or unproven.

Hydraulic Prosthetic Hip

Because the hip muscles are missing after hip disarticulation or hemipelvectomy amputation, prosthetic knees that require hip extension or force to be applied to the heel to achieve stability are contraindicated. The Helix3DHip manufacturer, OttoBock, states that the C-Leg microprocessor knee has stance resistance that does not require stabilization of the knee through hip extensor activity or by loading the heel, thereby ensuring stability. OttoBock has stated that the Helix3DHip requires a prosthetic knee that provides absolute stability and reliability at heel strike, stance extension damping, and swing extension damping. Therefore, OttoBock states that the Helix3DHip is only safe and guaranteed when used with the C-Leg microprocessor knee.

2013 Update

Microprocessor-Controlled and Powered Knee Prostheses

A search of peer reviewed literature through October 2013 identified no new clinical trial publications or any additional information that would change the coverage position for knee prostheses.

Microprocessor-Controlled and Powered Ankle-Foot Prostheses

A 2012 randomized within-subject crossover study compared self-reported and objective performance outcomes for 4 types of prosthetic feet, including the Proprio Foot. (42) Ten patients with transtibial amputation were tested with their own prosthesis and then after training and a 2-week acclimation period with the SACH (solid ankle cushion heel), SAFE (stationary attachment flexible endoskeletal), Talux, and Proprio Foot in a randomized order. No differences between prostheses were detected by the self-reported PEQ and Locomotor Capabilities Index, or for the objective 6-minute walk test. Steps per day and hours of daily activity between testing sessions did not differ between the types of prostheses.

In 2012, Ferris et al. reported a pre-post comparison of the PowerFoot Biom with the patient’s own energy-storing and -returning foot (ESR) in 11 patients with transtibial amputation. Results for both prostheses were also compared with 11 matched controls who had intact limbs. (43) In addition to altering biomechanical measures, the powered ankle-foot increased walking velocity compared to the ESR prosthesis and increased step length compared to the intact limb. There appeared to be an increase in compensatory strategies at proximal joints with the PowerFoot; the authors noted that normalization of gait kinematics and kinetics may not be possible with a uniarticular device. Physical performance measures were not significantly different between the 2 prostheses, and there were no significant differences between conditions on the PEQ. Seven patients preferred the PowerFoot and 4 preferred the ESR. Compared to controls with intact limbs, the PowerFoot had reduced range of motion, but greater ankle peak power.

Another similar, small pre- post- study from 2012 (7 amputees and 7 controls) found gross metabolic cost and preferred walking speed to be more similar to non-amputee controls with the PowerFoot Biom than with the patient’s own ESR. (44)

In a conference proceeding from 2011, Mancinelli et al. describe a comparison of a passive-elastic foot and the PowerFoot Biom in 5 transtibial amputees. (45) The study was supported by the U.S. Department of Defense, and, at the time of testing, the powered prosthesis was a prototype and subjects’ exposure to the prosthesis was limited to the laboratory. Laboratory assessment of gait biomechanics showed an average increase of 54% in the peak ankle power generation during late stance. Metabolic cost, measured by oxygen consumption while walking on an indoor track, was reduced by an average of 8.4% (p=0.06).

In 2013, Agrawal et al. (46) noted that prosthetic foot prescription guidelines lack scientific evidence and are concurrent with an amputee's concurrent with an amputee's Medicare Functional Classification Level (K-Level) and categorization of prosthetic feet. They conducted a randomized repeated-measures trial to evaluate the influence of gait training and four categories of prosthetic feet (K1, K2, K3, and microprocessor ankle/foot) on Symmetry in External Work for K-Level-2 and K-Level-3 unilateral transtibial amputees. Five K-Level-2 and five K-Level-3 subjects were tested in their existing prosthesis during Session 1 and again in Session 2, following 2 weeks of standardized gait training. In Sessions 3-6, subjects were tested using a study socket and one of four randomized test feet. There was an accommodation period of 10-14 days with each foot. Symmetry in External Work for positive and negative work was calculated at each session to determine symmetry of gait dynamics between limbs at self-selected walking speeds. K-Level-2 subjects had significantly higher negative work symmetry with the K3 foot, compared to K1/K2 feet. For both subject groups, gait training had a greater impact on positive work symmetry than test feet. The authors concluded that higher work symmetry is possible for K-Level-2 amputees who are trained to take advantage of K3 prosthetic feet designs; there exists a need for an objective determinant for categorizing and prescribing prosthetic feet.

Conclusions: Several small studies have been reported with micro-processor controlled and powered ankle-foot prostheses for transtibial amputees. Evidence to date is insufficient to support an improvement in functional outcomes when compared to energy-storing and -returning prostheses. Larger, higher quality, long term studies are needed to determine the impact of these devices on health outcomes with greater certainty.


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Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive.           

The presence or absence of procedure, service, supply, device or diagnosis codes in a Medical Policy document has no relevance for determination of benefit coverage for members or reimbursement for providers. Only the written coverage position in a medical policy should be used for such determinations.           

Benefit coverage determinations based on written Medical Policy coverage positions must include review of the member’s benefit contract or Summary Plan Description (SPD) for defined coverage vs. non-coverage, benefit exclusions, and benefit limitations such as dollar or duration caps.

ICD-9 Codes

84.10, 84.12, 84.13, 84.14, 84.15, 84.16, 84.17, 84.18, 84.19, 896, 896.0, 896.1, 896.2, 896.3, 897, 897.0, 897.1, 897.2, 897.3, 897.4, 897.5, 897.6, 897.7, V49.70, V49.71, V49.72, V49.73, V49.74, V49.75, V49.76, V49.77, V49.7

ICD-10 Codes

S78.011a, S78.012a, S78.019a, S78.021a, S78.022a, S78.029a, S78.111a, S78.112a, S78.119a, S78.121a, S78.122a, S78.129a, S78.911a, S78.912a, S78.919a, S78.921a, S78.922a, S78.929a, S88.011a, S88.012a, S88.019a, S88.021a, S88.022a, S88.029a, S88.111a, S88.112a, S88.119a, S88.121a, S88.122a, S88.129a, S88.911a, S88.912a, S88.919a, S88.921a, S88.922a, S88.929a, S98.011a, S98.012a, S98.019a, S98.911a, S98.912a, S98.919a, S98.019a, S98.319a, S98.919a, S98.911a, S98.912a, Z89.431, Z89.432, Z89.439, Z89.441, Z89.442, Z89.449, Z89.50, Z89.51, Z89.52, Z89.611, Z89.612, Z89.619, Z89.621, Z89.622, Z89.629, Z89.9, Z96.641, Z96.642, Z96.643, Z96.649, Z96.651, Z96.652, Z96.653, Z96.659, Z96.661, Z96.662, Z96.669

Procedural Codes: 97110, 97112, 97116, 97761, 97762, L5000, L5010, L5020, L5050, L5060, L5100, L5105, L5150, L5160, L5200, L5210, L5220, L5230, L5250, L5270, L5280, L5301, L5312, L5321, L5331, L5341, L5400, L5410, L5420, L5430, L5450, L5460, L5500, L5505, L5510, L5520, L5530, L5535, L5540, L5560, L5570, L5580, L5585, L5590, L5595, L5600, L5610, L5611, L5613, L5614, L5616, L5617, L5618, L5620, L5622, L5624, L5626, L5628, L5629, L5630, L5631, L5632, L5634, L5636, L5637, L5638, L5639, L5640, L5642, L5643, L5644, L5645, L5646, L5647, L5648, L5649, L5650, L5651, L5652, L5653, L5654, L5655, L5656, L5658, L5661, L5665, L5666, L5668, L5670, L5671, L5672, L5673, L5676, L5677, L5678, L5679, L5680, L5681, L5682, L5683, L5684, L5685, L5686, L5688, L5690, L5692, L5694, L5695, L5696, L5697, L5698, L5699, L5700, L5701, L5702, L5703, L5704, L5705, L5706, L5707, L5710, L5711, L5712, L5714, L5716, L5718, L5722, L5724, L5726, L5728, L5780, L5781, L5782, L5785, L5790, L5795, L5810, L5811, L5812, L5814, L5816, L5818, L5822, L5824, L5826, L5828, L5830, L5840, L5845, L5848, L5850, L5855, L5856, L5857, L5858, L5859, L5910, L5920, L5925, L5930, L5940, L5950, L5960, L5961, L5962, L5964, L5966, L5968, L5969, L5970, L5971, L5972, L5973, L5974, L5975, L5976, L5978, L5979, L5980, L5981, L5982, L5984, L5985, L5986, L5987, L5988, L5990, L5999, L7360, L7362, L7367, L7368, L7510, L7520, L7600, L8400, L8410, L8415, L8417, L8420, L8430, L8435, L8440, L8460, L8465, L8470, L8480, L8485, L8499
  1. Kirker, S., Keymer, S., et al. An assessment of the intelligent knee prosthesis. Clinical Rehabilitation 1996; 10(3):267-73.
  2. Buckley, J.G., Spence, W.D., et al. Energy cost of walking: comparison of “Intelligent Prosthesis” with conventional mechanism. Archives of Physical Medicine and Rehabilitation 1997; 78(3):330-3.
  3. Datta, D., and J. Howitt. Conventional versus microchip controlled pneumatic swing phase control for trans-femoral amputees: user’s verdict. Prosthetics and Orthotics International 1998; 22(2):129-35.
  4. Michael, J.W. Modern prosthetic knee mechanisms. Clinical Orthopaedics and Related Research 1999; (361):39-47.
  5. Angelico, John. Transfemoral Prosthetics, Above Knee. InMotion (May/June 1999) 9(3). (Accessed 2005 March).
  6. U.S. Department of Veterans Affairs, Veterans Health Administration, Office of Research and Development, Health Service Research and Development Service, Management Decision and Research Center, Technology Assessment Program. Computerized lower limb prosthesis. VA Technology Assessment Program Short Report No. 2. Boston, Mass: MDRC, March 2000. Available at (Accessed 2011 March).
  7. Miller, W.C., Speechley, M., et al. The prevalence and risk factors of falling and fear of falling among lower extremity amputees. Archives of Physical Medicine and Rehabilitation 2001; 82:1031-6.
  8. Miller, W.C., Deathe, B., et al. The influence of falling, fear of falling, and balance confidence on prosthetic mobility and social activity among individuals with a lower extremity amputation. Archives of Physical Medicine and Rehabilitation 2001; 82:1238-44.
  9. Hafner, Brian J., et al. Transtibial energy-storage-and-return prosthetic devices: A review of energy concepts and a proposed nomenclature. Journal of Rehabilitation Research and Development 2002; 39(1):1-11. Available at (Accessed 2005 March).
  10. Baum, Robert. VA Embraces gait and limb technology. Capabilities. Northwestern University Prosthetics Research Laboratory and Rehabilitation Engineering Research Program 2002; 11(2):11-13. Available at (Accessed 2005 July)
  11. Bodeau, Valerie S., et al. Lower limb prosthetics 2002; Available at (Accessed 2005 March).
  12. Miller, W.C., Speechley, M., et al. Balance confidence among people with lower limb amputations. Physical Therapy 2002; 82:9:856-65.
  13. Technology Assessment, Microprocessor-Controlled Prosthetic Knees. State of Washington Department of Labor and Industries, Office of Medical Directory 2002. Available at (Accessed 2005 July).
  14. Van der Linde, Hofstadt, C.J. et al. A systematic literature review of the effect of different prosthetic components on human functioning with a lower-limb prosthesis. Journal of Rehabilitation Research and Development 2004; 41(4):555-70.
  15. Smith, Douglas G. The transfemoral amputation level, Part 4, Great prosthetic components are good, but a good socket is great. InMotion 2004; 14(5).
  16. General Prosthetic Services. Orthotics and Prosthetics Rehabilitation Engineering Centre. Available at (Accessed 2005 February).
  17. VHA Prosthetic Clinical Management Program (PCMP). Clinical practice recommendations: microprocessor knees, 2004. See: Berry D. Microprocessor prosthetic knees. Phys Med Rehabil Clin N Am 2006; 17:91-113.
  18. Hofstad C, Linde H, Limbeek J et al. Prescription of prosthetic ankle-foot mechanisms after lower limb amputation. Cochrane Database Syst Rev 2004; (1):CD003978.
  19. 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.
  20. Prosthetic knees. National Amputee Centre. The War Amps©2005. Available at (Accessed 2005 March).
  21. Manual for below-knee amputees. OMNI (Organising Medical Networked Information). University of Nottingham, UK. Available at (Accessed 2005 July).
  22. Manual for above-knee amputees. OMNI (Organising Medical Networked Information). University of Nottingham, UK. Available at (Accessed 2005 July).
  23. 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):563-75.
  24. Swanson E, Stube J, Edman P. Function and body image levels in individuals with transfemoral amputations using the C-Leg. J Prosthet Orthot 2005; 17(3): 80-4.
  25. Pauley, T., Devlin, M., et al. Falls sustained during inpatient rehabilitation after lower limb amputation: prevalence and predictors. American Journal of Physical Medicine and Rehabilitation 2006; 85:521-32.
  26. Department of Veterans Affairs Fact Sheet, VA’s Prosthetics and Sensory Aids. February 2006. Available at: (Accessed March 2007).
  27. Orendurff MS, Segal AD, Klute GK et al. Gait efficiency using the C-Leg. J Rehabil Res Dev 2006; 43(2):239-46.
  28. Klute GK, Berge JS, Orendurff MS et al. Prosthetic intervention effects on activity of lower-extremity amputees. Arch Phys Med Rehabil. 2006; 87(5):717-22.
  29. 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):989-94.
  30. 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):207-17.
  31. Seymour R, Engbretson B, Kott K et al. Comparison between the C-leg(R) 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.
  32. 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):489-93.
  33. 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):1380-5.
  34. Bionic Technology - Proprio Foot, Walk Your Way. Ossur. 2002-2008. Available at (Accessed 2008 September 4).
  35. LCD for Lower Limb Prostheses (L11464). Available at (Accessed 2009 January).
  36. Hafner BJ, Smith DG. Differences in function and safety between Medicare Functional Classification Level-2 and -3 transfemoral amputees and influence of prosthetic knee joint control. J Rehabil Res Dev 2009; 46(3):417-33.
  37. 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):356-63.
  38. Au S, Berniker M, Herr H. Powered ankle-foot prosthesis to assist level-ground and stair-descent gaits. Neural Netw 2008; 21(4):654-66.
  39. Patient Indications: List of indications for the C-Leg and Compact. Otto Bock, U.S. Available at: (Accessed January 2009).
  40. Hofstad CJ, van der Linde H, et al. There is not enough evidence to establish precise criteria for the prescription of prosthetic ankle-foot mechanisms in individuals with a lower limb amputation. Cochrane Summary. Published Online January 21, 2009.
  41. Fradet L, Alimusaj M, Braatz F et al. Biomechanical analysis of ramp ambulation of transtibial amputees with an adaptive ankle foot system. Gait Posture 2010; 32(2):191-8.
  42. Gailey RS, Gaunaurd I, Agrawal V et al. Application of self-report and performance-based outcome measures to determine functional differences between four categories of prosthetic feet. J Rehabil Res Dev 2012; 49(4):597-612.
  43. Ferris AE, Aldridge JM, Rabago CA et al. Evaluation of a powered ankle-foot prosthetic system during walking. Arch Phys Med Rehabil 2012; 93(11):1911-8.
  44. Herr HM, Grabowski AM. Bionic ankle-foot prosthesis normalizes walking gait for persons with leg amputation. Proc Biol Sci 2012; 279(1728):457-64.
  45. Mancinelli C, Patritti BL, Tropea P et al. Comparing a passive-elastic and a powered prosthesis in transtibial amputees. Conf Proc IEEE Eng Med Biol Soc 2011; 2011:8255-8.
  46. Agrawal V, Gailey R, et al. Influence of gait training and prosthetic foot category on external work symmetry during unilateral transtibial amputee gait. Prosthet Orthot Int. 2013 Oct; 37(5):396-403. Epub 2013 Jan 30.
  47. Endolite Êlan. Products, Êlan Description. (Accessed November 11, 2013.
  48. Microprocessor-Controlled Prosthetic Knees. Chicago, Illinois: Blue Cross Blue Shield Association Medical Policy Reference Manual (2013 March) Durable Medical Equipment 1.04.05.
April 2013  New 2013 BCBSMT medical policy.
February 2014 Document updated with literature review. No changes to Coverage. “Êlan® (Endolite)” was added as an example of a microprocessor-controlled foot/ankle.
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Lower Limb Prosthetics, Including Microprocessor Prosthetics