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Microprocessor-Controlled Prostheses for the Lower Limb

Policy Number: MP-083

Latest Review Date: March 2022

Category: DME 


 A microprocessor-controlled knee may be considered medically necessary in individuals with transfemoral amputation and ALL the following indications are met:

  • The patient is fit and active Physical ability, including adequate cardiovascular and pulmonary reserve, for ambulation at faster than normal walking speed, with at least a potential Functional Level 3 or 4;
  • The patient has the appropriate cognitive abilities to master use and care requirements for the technology;
  • The patient does not have additional medical problems that would interfere with maintaining functional level 3 or 4: i.e., disabling cardiovascular, neuromuscular, peripheral vascular, or musculoskeletal (other than amputation) conditions.

Refer to Coding Section for guidelines regarding the Ottobock Genium® MPK

 A microprocessor-controlled knee is contraindicated when:

  • Patient is historically non-ambulatory or has a potential functional level below 3.
  • Patient has demonstrated a lack of proper care for existing equipment.
  • Patient is not motivated.
  • Patient lives or works in a wet environment.

Coverage may be provided for one microprocessor-controlled knee per limb per five years when medically indicated. Coverage will not be provided if the prosthesis is functioning properly and in good general condition.

A high activity knee control frame (L5930) is only covered for patients whose functional level is K4.

A power knee is considered investigational.

A microprocessor-controlled or powered foot is considered investigational. 

A combination microprocessor-controlled powered foot and microprocessor-controlled knee prosthesis is considered investigational.

A combination microprocessor-controlled knee/ankle/foot (i.e. Linx) is considered investigational.

Additions or upgrades to the prosthetic for convenience, sports or recreational activities are considered not medically necessary.


Microprocessor-controlled prostheses use feedback from sensors to adjust joint movement on a real-time as-needed basis.  Active joint control is intended to improve safety and function, particularly for patients who have the capability to maneuver on uneven terrain and with variable gait. 

Lower Extremity Prosthetics

More than 100 different prosthetic ankle-foot and knee 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 differ from those of a younger, active person. Key elements of a prosthetic knee design involve providing stability during both the stance and swing phase of the gait. Prosthetic knees 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 of 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 if the cadence is altered. When properly controlled, hydraulic or pneumatic swing-phase controls allow the prosthetist to set a pace adjusted to the individual amputee, from very slow to a race-walking pace. Hydraulic prostheses are heavier than other options and require gait training; for these reasons, these prostheses are 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.

Amputees should be evaluated by an independent, qualified professional to determine the most appropriate prosthetic components and control mechanism. A trial period may be indicated to evaluate the tolerability and efficacy of the prosthesis in a real-life setting. Decisions about the potential benefits of microprocessor knees involve multiple factors including activity levels and the patient's physical and cognitive ability. A patient's need for daily ambulation of at least 400 continuous yards, daily and frequent ambulation at variable cadence or on uneven terrain (e.g., gravel, grass, curbs), and daily and frequent use of ramps and/or stairs (especially stair descent) should be considered as part of the decision. Typically, the daily and frequent need of 2 or more of these activities would be needed to show benefit.

The following are guidelines from the Veterans Health Administration Prosthetic Clinical Management Program Clinical Practice Recommendations for Microprocessor Knees.

A. Contraindications for the use of the microprocessor knee should include the following:

  • Any condition that prevents socket fitting, such as a complicated wound or intractable pain which precludes socket wear
  • Inability to tolerate the weight of the prosthesis
  • Medicare level K0-no ability or potential to ambulate or transfer
  • Medicare level K1-limited ability to transfer or ambulate on level ground at fixed cadence
  • Medicare level K2-limited community ambulator who does not have the cardiovascular reserve, strength, and balance to improve stability in stance to permit increased independence, less risk of falls, and potential to advance to a less restrictive walking device
  • Inability to use swing and stance features of the knee unit
  • Poor balance or ataxia that limits ambulation
  • Significant hip flexion contracture (>20°)
  • Significant deformity of remaining limb that would impair the ability to stride
  • Limited cardiovascular and/or pulmonary reserve or profound weakness
  • Limited cognitive ability to understand gait sequencing or care requirements
  • Long-distance or competitive running
  • Falls outside of recommended weight or height guidelines of the manufacturer
  • Specific environmental factors such as excessive moisture or dust, or inability to charge the prosthesis
  • Extremely rural conditions where maintenance ability is limited.

B. Indications for the use of the microprocessor knee should include the following:

  • Adequate cardiovascular and pulmonary reserve to ambulate at variable cadence
  • Adequate strength and balance in stride to activate the knee unit
  • Should not exceed the weight or height restrictions of the device
  • Adequate cognitive ability to master technology and gait requirements of the device
  • Hemi-pelvectomy through knee-disarticulation level of amputation, including bilateral; lower-extremity amputees are candidates if they meet functional criteria as listed
  • The patient is an active walker and requires a device that reduces energy consumption to permit longer distances with less fatigue
  • Daily activities or job tasks that do not permit full focus of concentration on knee control and stability-such as uneven terrain, ramps, curbs, stairs, repetitive lifting, and/or carrying
  • Medicare level K3-unlimited community ambulator
  • Medicare level K4-active adult, athlete who needs to function as a K3 level in daily activities
  • Potential to lessen back pain by providing more secure stance control, using less muscle control to keep the knee stable
  • Potential to unload and decrease stress on remaining limb
  • Potential to return to an active lifestyle.

C. Physical and Functional Fitting Criteria for New Amputees:

  • New amputees may be considered if they meet certain criteria as outlined above
  • Premorbid and current functional assessment important determinant
  • Requires stable wound and ability to fit the socket
  • Immediate postoperative fit is possible
  • Must have potential to return to an active lifestyle


The most recent literature update was performed through January 24, 2022.


For individuals who have a transfemoral amputation who receive a prosthesis with a microprocessor-controlled knee, the evidence includes a number of within-subject comparisons of microprocessor-controlled knees vs non-microprocessor-controlled knee joints. Relevant outcomes are functional outcomes, health status measures, and quality of life. For K3- and K4-level amputees, studies have shown an objective improvement in function on some outcome measures, particularly for hill and ramp descent, and strong patient preference for microprocessor-controlled prosthetic knees. Benefits include a more normal gait, increased stability, and a decrease in falls. The potential to achieve a higher functional level with a microprocessor-controlled knee includes having the appropriate physical and cognitive ability to use the advanced technology. The evidence is sufficient to determine that the technology results in an improvement in the net health outcome.

For individuals who have a transfemoral amputation who receive a prosthesis with a powered knee, the evidence includes no data. Relevant outcomes are functional outcomes, health status measures, and quality of life. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.

For individuals who have a tibial amputation who receive a prosthesis with a microprocessor-controlled ankle-foot, the evidence includes no data. Relevant outcomes are functional outcomes, health status measures, and quality of life. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.

For individuals who have a tibial amputation who receive a prosthesis with a powered ankle-foot, the evidence includes limited data. Relevant outcomes are functional outcomes, health status measures, and quality of life. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.


U.S Department of Veterans Affairs/Department of Defense

In 2019, the Veterans Affairs/Department of Defense Clinical Practice Guideline for Rehabilitation of Individuals with Lower Limb Amputation made the following recommendations:

We suggest offering microprocessor knee units over non-microprocessor knee units for ambulation to reduce risk of falls and maximize patient satisfaction. There is insufficient evidence to recommend for or against any particular socket design, prosthetic foot categories, and suspensions and interfaces.

U.S. Preventive Services Task Force Recommendations

Not applicable.


C-leg, microprocessor control prostheses, computerized leg, computerized lower limb prosthesis, bionic leg, Proprio Foot®, Power Foot, microprocessor-controlled foot, power knee, powered foot, iPED, Intelligent Prosthesis,  Symbionic® Leg, PowerFoot Biom, Genium, Otto Bock®, Rheo Knee, Linx system (endolite), knee/ankle/foot/prosthesis system, ALLUX


According to the manufacturers, microprocessor-controlled prostheses are considered a Class I device by the FDA and are exempt from 510(k) requirements. This classification does not require submission of clinical data regarding efficacy but only notification of FDA prior to marketing.


Coverage is subject to member’s specific benefits.  Group specific policy will supersede this policy when applicable.

ITS: Home Policy provisions apply

FEP contracts: Special benefit considerations may apply.  Refer to member’s benefit plan.  FEP does not consider investigational if FDA approved and will be reviewed for medical necessity.


HCPCS codes:  

K1014 Addition, endoskeletal knee-shin system, 4 bar  linkage or multiaxial, fluid swing and stance phase control (Effective 4/1/21)


Addition, endoskeletal, knee-shin system, single axis, fluid swing and stance phase control


Addition, endoskeletal system, high activity knee control frame


Stance extension, damping, adjustable


Addition to endoskeletal knee-shin system, fluid stance extension, dampening feature, with or without adjustability


Addition, endoskeletal system above knee or hip disarticulation, knee extension assist


Addition to lower extremity prosthesis, endoskeletal knee-shin system, powered and programmable flexion/extension assist control, includes any type motor(s)


Addition, endoskeletal ankle-foot or ankle system, power assist, includes any type motor(s)

There are specific HCPCS codes that describe the microprocessor-controlled knee prosthesis:


Addition to lower extremity prosthesis, endoskeletal knee-shin system, microprocessor control feature, swing and stance phase, includes electronic sensor(s), any type


Addition to lower extremity prosthesis, endoskeletal knee-shin system, microprocessor control feature, swing phase only, includes electronic sensor(s), any type


Addition to lower extremity prosthesis, endoskeletal knee shin system, microprocessor control feature, stance phase only, includes electronic sensor(s), any type

There is a specific HCPCS code for ankle-foot system with a microprocessor control feature:


Endoskeletal ankle foot system, microprocessor controlled feature, dorsiflexion and/or plantar flexion control

Ottobock Genium® MPK:

There is no separate billing and reimbursement for any other features or functions performed by the on-board microprocessors and/or sensors (e.g. L5999 “real-time gait assessment”, “electronically controlled static stance regulator, adjustable”, “predicted proprioceptive input” or programming necessary for use), since the allowance for all functions and features is included in the payment for codes recommended (L5828, L5845, L5848, L5856).


  1. Bellmann M, Schmalz T, Ludwigs E et al. Immediate effects of a new microprocessor-controlled prosthetic knee joint: a comparative biomechanical evaluation. Arch Phys Med Rehabil 2012; 93(3):541-9.
  2. 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.
  3. Carse B, Scott H, Brady L, et al. Evaluation of gait outcomes for individuals with established unilateral transfemoral amputation following the provision of microprocessor controlled knees in the context of a clinical service. Prosthet Orthot Int. Jun 01 2021;45(3): 254-261.
  4. 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.
  5. Delussu AS, Brunelli S, Paradisi F et al. Assessment of the effects of carbon fiber and bionic foot during over ground and treadmill walking in transtibial amputees. Gait Posture 2013; 38(4):876-82.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. Herr HM, Grabowski AM. Bionic ankle-foot prosthesis normalizes walking gait for persons with leg amputation. Proc Biol Sci 2012; 279(1728):457-64.
  11. Highsmith MJ, Kahle JT, Bongiorni DR et al. Safety, energy efficiency, and cost efficacy of the C-Leg for transfemoral amputees: a review of the literature. Prosthet Orthot Int 2010; 34(4):362-77.
  12. Highsmith MJ, Kahle JT, Miro RM et al. Ramp descent performance with the C-Leg and interrater reliability of the Hill Assessment Index. Prosthet Orthot Int. 2013 Oct; 37(5):362-8.
  13. Howard CL, Wallace C, Perry B, et al. Comparison of mobility and user satisfaction between a microprocessor knee and a standard prosthetic knee: a summary of seven single-subject trials. Int J Rehabil Res. Mar 2018; 41(1):63-73
  14. IOM (Institute of Medicine). 2011. Clinical Practice Guidelines We Can Trust. Washington, DC: The National Academies Press.
  15. Kaufman, KK, Bernhardt, KK, Symms, KK. Functional assessment and satisfaction of transfemoral amputees with low mobility (FASTK2): A clinical trial of microprocessor-controlled vs. non-microprocessor-controlled knees. Clin Biomech (Bristol, Avon), 2018 Aug 5; 58:116-122.
  16. LCD for Lower Limb Prostheses (L11464). Accessed February, 2015.
  17. 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. Aug 2011; 2011:8255-8258.
  18. Noridian Healthcare Solutions. Notification of Service Specific Targeted Review of Lower Limb Prostheses (HCPCS L5980). 2018; Accessed April 9, 2018.
  19. Prinsen EC, Nederhand MJ, Olsman J, et al. Influence of a user-adaptive prosthetic knee on quality of life, balance confidence, and measures of mobility: a randomized cross-over trial. Clin Rehabil. Oct 6 2014.
  20. Rosenblatt N, Brauer A, Rotter D et al. Active dorsiflexing prostheses may reduce tri-related fall-risk. AAOP Journal of Proceedings 2014,
  21. Theeven PJ, Hemmen B, Geers RP, et al. Influence of advanced prosthetic knee joints on perceived performance and everyday life activity level of low-functional persons with a transfemoral amputation or knee disarticulation. J Rehabil Med. May 2012; 44(5):454-461.
  22. 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):906-15.
  23. Thomas-Pohl M, Villa C, Davot J, et al. Microprocessor prosthetic ankles: comparative biomechanical evaluation of people with transtibial traumatic amputation during standing on level ground and slope. Disabil Rehabil Assist Technol. Jan 2021; 16(1): 17-26.
  24. United States Department of Veterans Affairs. VA technology assessment program project report – Patient summary on computerized lower limb prostheses. Available online at Last accessed August 2013. 
  25. Webster JB, Crunkhorn A, Sall J, et al. Clinical Practice Guidelines for the Rehabilitation of Lower Limb Amputation: An Update from the Department of Veterans Affairs and Department of Defense. Am J Phys Med Rehabil. Sep 2019; 98(9): 820-829.


Medical Policy Group, September 2002

Medical Policy Group, November 2002 (2)

Medical Policy Administration Committee May 2003

Available for comment May 23-July 7, 2003

Medical Policy Group, April 2004

Medical Policy Group, November 2005 (2)

Medical Policy Group, May 2007 (1)

Medical Policy Group, August 2007 (1)

Medical Policy Administration Committee, August 2007

Available for comment August 13-September 27, 2007

Medical Policy Group, February 2009 (2)

Medical Policy Administration Committee, March 2009

Available for comment March 4-April 17, 2009

Medical Policy Group, February 2010 (2)

Medical Policy Administration Committee February 2010

Medical Policy Group, November 2012: Added new 2013 Code L5859 effective 1/1/13; Deleted Code K0670 which deleted 1/1/06.

Medical Policy Panel, March 2013

Medical Policy Group, August 2013 (2): Policy updated with literature review through July 2013.  Added an investigational statement for combination microprocessor knee and power foot prostheses.  Description, Key Words, Key Points, Codes, and References updated.

Medical Policy Administration Committee, September 2013.

Available for comment September 19 through November 2, 2013

Medical Policy Group, December 2013 (5):  2014 Coding Update – added new code L5969 to current coding effective 01/01/2014

Medical Policy Group, February 2014 (5): Update to Policy statement to only cover code L5930 for functional level of K4.  Key Points and References also updated.

Medical Policy Administration Committee, February 2014

Available for comment February 5 through March 21, 2014

Medical policy Group, June 2014 (5): Updated description, Key Points and References; Policy statements unchanged.

Medical Policy Group, February 2015 (6): Updated References; no change to policy statement.

Medical Policy Panel, April 2015

Medical Policy Group, April 2015 (6): Updates to Description, Key Points, Key Words and References; no change to policy statement.

Medical Policy Group, November 2016 (6): Updates to coding section:L5848: Addition to endoskeletal knee-shin system, fluid stance extension, dampening feature, with or without adjustability.

Medical Policy Panel, November 2017

Medical Policy Group, November 2017 (6): Removed old policy statement. Added “A combination microprocessor-controlled knee/ankle/foot (i.e. Linx) does not meet Blue Cross and Blue Shield medical criteria for coverage and is considered investigational.” to policy statement from existing investigational listing. Updates to Key Points, Governing Bodies, Key Words and References.

Medical Policy Panel, April 2018

Medical Policy Group, May 2018 (6): Updates to Description, Key Points, Practice Guidelines and References.

Medical Policy Panel, March 2019

Medical Policy Group, April 2019 (6): Updates to Description, Key Points, References and Title name changed to Microprocessor-Controlled Prostheses for the Lower Limb. No change to policy statement.

Medical Policy Group, June 2019 (6): Updates to Coding to include guidelines for the Ottobock Genium MPK.

Medical Policy Panel, March 2020

Medical Policy Group, March 2020 (6): Updates to Key Points, Practice Guidelines and References. Updated policy verbiage to include "microprocessor controlled knee" and "transfemoral amputation".

Medical Policy Panel, March 2021

Medical Policy Group, March 2021 (6): Updates to Key Points. Policy statement updated to remove “not medically necessary,” no change to policy intent.

Medical Policy Group, March 2021: Quarterly Coding Update.  Added new code K1014 to Current Coding. Added Key Word ALLUX.

Medical Policy Group, September 2021 (6): Added clarification statement to include non-coverage for convenience items.

Medical Policy Panel, March 2022

Medical Policy Group, March 2022 (6): Updates to Policy statement, Description, Key Points, Practice Guidelines and References. No change to policy intent.

This medical policy is not an authorization, certification, explanation of benefits, or a contract. Eligibility and benefits are determined on a case-by-case basis according to the terms of the member’s plan in effect as of the date services are rendered. All medical policies are based on (i) research of current medical literature and (ii) review of common medical practices in the treatment and diagnosis of disease as of the date hereof. Physicians and other providers are solely responsible for all aspects of medical care and treatment, including the type, quality, and levels of care and treatment.

This policy is intended to be used for adjudication of claims (including pre-admission certification, pre-determinations, and pre-procedure review) in Blue Cross and Blue Shield’s administration of plan contracts.

The plan does not approve or deny procedures, services, testing, or equipment for our members. Our decisions concern coverage only. The decision of whether or not to have a certain test, treatment or procedure is one made between the physician and his/her patient. The plan administers benefits based on the member’s contract and corporate medical policies. Physicians should always exercise their best medical judgment in providing the care they feel is most appropriate for their patients. Needed care should not be delayed or refused because of a coverage determination.

As a general rule, benefits are payable under health plans only in cases of medical necessity and only if services or supplies are not investigational, provided the customer group contracts have such coverage.

The following Association Technology Evaluation Criteria must be met for a service/supply to be considered for coverage:

1. The technology must have final approval from the appropriate government regulatory bodies;

2. The scientific evidence must permit conclusions concerning the effect of the technology on health outcomes;

3. The technology must improve the net health outcome;

4. The technology must be as beneficial as any established alternatives;

5. The improvement must be attainable outside the investigational setting.

Medical Necessity means that health care services (e.g., procedures, treatments, supplies, devices, equipment, facilities or drugs) that a physician, exercising prudent clinical judgment, would provide to a patient for the purpose of preventing, evaluating, diagnosing or treating an illness, injury or disease or its symptoms, and that are:

1. In accordance with generally accepted standards of medical practice; and

2. Clinically appropriate in terms of type, frequency, extent, site and duration and considered effective for the patient’s illness, injury or disease; and

3. Not primarily for the convenience of the patient, physician or other health care provider; and

4. Not more costly than an alternative service or sequence of services at least as likely to produce equivalent therapeutic or diagnostic results as to the diagnosis or treatment of that patient’s illness, injury or disease.