Clinical UM Guideline

This document addresses the use of lower limb prostheses required to replace the function of a lower limb loss due to trauma, disease, or a congenital condition.

Note: For information addressing lower limb prosthesis please refer to:

• CG-OR-PR-08 Microprocessor Controlled Lower Limb Prosthesis
• CG-OR-PR-10 Osseointegrated Limb Prostheses

Note: For a high-level overview of this document, please see “Summary for Members and Families” below. 

I.  Lower Limb: Prosthesis Fitting and Selection

Medically Necessary:

A lower limb prosthesis is considered medically necessary when all the following are met and are documented in the medical record:

1. The prosthesis is prescribed by physician; and
2. The member will reach or maintain a defined functional state within a reasonable period of time; and
3. The member needs the prosthesis for ambulation; and
4. The member’s rehabilitation potential is based on Functional Levels (also known as ‘K-Levels’, see Discussion section below for more information); and
5. The following anatomy-specific criteria apply:
   1. Ankles:
      An axial rotation unit is considered medically necessary for individuals whose functional level is 2 or above.
   2. Knees:
      Basic lower extremity prostheses include a single axis, constant friction knee. Prosthetic knees are considered for medical necessity based upon functional classification:
      1. Fluid and pneumatic knees are considered medically necessary for members with a functional Level 3 or above.
      2. Other knee systems are considered medically necessary for members with a functional Level 1 or above.
   3. Feet:
      The treating physician or the prosthetist will make the determination of the type of foot needed for the prosthesis based upon the functional needs of the individual. Basic lower extremity prostheses include a SACH foot. Other prosthetic feet are considered for medical necessity based upon functional classification.
      1. An external keel SACH foot or single axis ankle/foot is considered medically necessary for individuals whose functional level is 1 or above.
      2. A flexible-keel foot or multi-axial ankle/foot is considered medically necessary for individuals whose functional level is 2 or above.
      3. A flex foot system, energy storing foot, multi-axial ankle/foot, dynamic response, or flex-walk system or equal, or shank foot system with vertical loading pylon is considered medically necessary for individuals whose functional level is 3 or above.

Not Medically Necessary:

A lower limb prosthesis is considered not medically necessary when the criteria above have not been met, including but not limited to the following:

1. For individuals with a functional level of 0;
2. Prosthetics utilized primarily for leisure or sporting activities.

II.  Lower Limb: Accessories, Maintenance, Repairs and Replacement

Medically Necessary:

Up to two test (diagnostic) sockets for an individual prosthesis are medically necessary without additional documentation.

Replacement sockets are considered medically necessary if there is adequate functional documentation of physiological need, including, but not limited to:

1. Changes in the residual limb; or
2. Functional need changes; or
3. Irreparable damage; or
4. Wear/tear due to excessive member weight or prosthetic demands of very active amputees.

Accessories (for example, stump stocking for the residual limb, harness, etc.) are considered medically necessary when these appliances aid in, or are essential to, the effective use of the artificial limb.

Repairs to a prosthesis are considered medically necessary when necessary to make the prosthesis functional.

Maintenance that may be necessitated by manufacturer’s recommendations or the construction of the prosthesis and must be performed by the prosthetist is considered medically necessary as a repair.

Adjustments to a prosthesis required by wear and tear or change in an individual’s condition are considered medically necessary.

Replacement of a prosthesis or prosthetic component is considered medically necessary if the treating physician orders a replacement device or part because of either of the following:

1. A change in the physiological condition of the individual; or
2. Irreparable wear of the device or a part of the device.

Not Medically Necessary:

Test (diagnostic) sockets for immediate post-surgical or early fitting prostheses are considered not medically necessary.

More than two test (diagnostic) sockets for an individual prosthesis are considered not medically necessary without additional documentation of need.

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

Prosthetic accessories, additions, or components used primarily for leisure or sporting activities are considered not medically necessary under all conditions.

This document describes clinical studies and expert recommendations, and explains whether lower limb prostheses are clinically appropriate. The following summary does not replace the medical necessity criteria or other information in this document. The summary may not contain all of the relevant criteria or information. This summary is not medical advice. Please check with your healthcare provider for any advice about your health.

Key Information

A lower limb prosthesis is an artificial limb used to replace part or all of a missing leg. It can help people stand, walk, transfer from one surface to another, and perform daily activities. Prostheses may include different parts, such as feet, knees, ankles, sockets for the remaining limb, and accessories. The type of prosthesis needed depends on several factors, including the location where the limb is missing, a person's functional abilities, rehabilitation goals, and anticipated use. Healthcare providers use Functional Levels (also called K-Levels) to help determine which prosthetic components may be appropriate. Accessories, repairs, maintenance, adjustments, and replacement parts may also be appropriate when needed to support safe and effective use of the prosthesis.

What the Studies Show

Lower limb prostheses are widely used and are considered a standard part of care for people who have lost a leg because of injury, disease, or a condition present at birth. Research has looked at different prosthetic designs, including different types of foot and ankle devices. Some studies suggest that certain designs may provide small benefits in walking performance for some people. However, better studies are needed to know whether one prosthetic design improves health more than another.

Research reviews have found that it is difficult to predict which prosthetic design will work best for a specific person. Available studies often have limitations and inconsistent results. Expert recommendations recommend looking at the whole person, including health status, physical abilities, goals, and likely walking ability. Prosthetic accessories, repairs, maintenance, adjustments, and replacement parts may help keep the device working safely and effectively. Potential concerns with leg prosthetics may include include poor fit, wear and tear due to use, reduced function, or changes in a person’s body that may require adjustment or replacement.

When is a Lower Limb Prosthesis Clinically Appropriate?

A lower limb prosthesis may be appropriate in these situations:

• The prosthesis is prescribed by a physician; and
• The person is expected to reach or maintain a defined level of function within a reasonable period of time; and
• The prosthesis is needed for walking (ambulation); and
• Rehabilitation potential is evaluated using Functional Levels (K-Levels); and
• The appropriate anatomy-specific requirements below are met.

For ankle components:

• An axial rotation unit may be appropriate for people with Functional Level 2 or higher.

For knee components:

• Fluid or pneumatic knees may be appropriate for people with Functional Level 3 or higher.
• Other knee systems may be appropriate for people with Functional Level 1 or higher.

For foot components:

• An external keel SACH (solid ankle cushioned heel) foot or single-axis ankle/foot may be appropriate for people with Functional Level 1 or higher.
• A flexible-keel foot or multi-axial ankle/foot may be appropriate for people with Functional Level 2 or higher.
• An energy-storing foot, dynamic response foot, flex-foot system, flex-walk system, shank foot system with vertical loading pylon, or similar device may be appropriate for people with Functional Level 3 or higher.

For sockets:

• Up to two test (diagnostic) sockets may be appropriate for each prosthesis.
• Socket replacement may be appropriate when there is a documented need due to changes in the residual limb, changes in function, irreparable damage, or significant wear and tear.

Accessories, maintenance, repairs, adjustments, and replacement may be appropriate when they are needed to support effective use of the prosthesis or restore its function.

Replacement of a prosthesis or prosthetic component may be appropriate when:

• There has been a change in the person's physical condition; or
• The device or component has irreparable wear or damage.

When is this not Clinically Appropriate?

A lower limb prosthesis is not clinically appropriate when the criteria listed above are not met, including for people with Functional Level 0. Functional Level 0 means the person does not have the ability or expected ability to safely walk or transfer with a prosthesis, and the prosthesis would not improve mobility or quality of life.

Prostheses, accessories, additions, or components used mainly for leisure or sporting activities are not clinically appropriate because they are intended for recreational purposes rather than routine medical needs.

(Return to Description)

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

When services may be Medically Necessary when criteria are met:

Associated Coding

When services may also be Medically Necessary for related services and components when criteria are met for the prosthesis:

When services are Not Medically Necessary:
For the procedure codes listed above when criteria are not met or for situations designated in the Clinical Indications section as not medically necessary.

Summary

The use of mechanical lower limb prosthetic devices is widely recognized as consistent with generally accepted standards of medical practice for individuals with extremity amputations from any cause. As supported by the guidelines of the Centers for Medicare & Medicaid Services [CMS], the need for a specific type of mechanical prosthetic limb and related components/additions is based upon demonstrated medical need, ability to utilize a particular device, and the expectations of the ordering provider regarding the likely post-treatment functional level.

Similarly, the use of accessories to lower limb prosthesis such as stump stockings, harness, etc. are considered a necessary component of care when they support or are essential to the effective use of the prosthetic device.

Repairs, maintenance, and adjustments to a prosthesis are necessary when required to keep or make the prosthesis functional. Such services should be made by a qualified prosthetist in compliance with the manufacturer’s recommendations in order to assure the best outcomes.

Finally, replacement of a prosthesis or a component of such a device is sometimes necessary. As noted below, CMS recognizes several circumstances for replacement, including when the treating physician observes a change in the physiological condition of the individual, such as weight loss or growth, that significantly impact the fit of the device. Additionally, as with any device that undergoes regular use, wear and deterioration of the device and its components may result in impaired function necessitating replacement when repair is not possible.

Discussion

Potential functional ability is based upon many factors, including but not limited to:

1. The individual’s past history and level of activity (including prior prosthetic use if applicable).
2. The individual’s current condition including the status of the residual limb and the nature of other medical problems.
3. The individual’s likely ability for community-based ambulation.

Functional Levels, also known as ‘K Levels’, are used to guide the appropriateness of lower limb prosthesis (Balk, 2018; CMS, 2017). Please note that within the functional classification hierarchy, bilateral amputees often cannot be strictly bound by functional level classifications.

Level 0:   Does not have the ability or potential to ambulate or transfer safely with or without assistance and prosthesis does not enhance their quality of life or mobility.
Level 1:   Has the ability or potential to use prosthesis for transfers or ambulation on level surfaces at fixed cadence. Typical of the limited and unlimited household ambulator.
Level 2:   Has the ability or potential for ambulation with the ability to traverse low-level environmental barriers such as curbs, stairs or uneven surfaces. Typical of the limited community ambulator.
Level 3:   Has the ability or potential for ambulation 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 ambulation that exceeds basic ambulation skills, exhibiting high impact, stress, or energy levels. Typical of the prosthetic demands of the child, active adult, or athlete.

Hofstad and colleagues (2004) published a systematic review evaluating prosthetic ankle-foot mechanisms and the impact of daily functioning of individuals with lower limb amputation. A total of 26 studies were included, with a total of 245 individuals. The data indicated there may be a slight advantage in stride length and energy cost for individuals with transfemoral amputation utilizing the Flex-foot on level walking ground. However, the authors concluded that overall, there is insufficient evidence to conclude that one prosthetic design is superior to another, such as the Flex-foot versus the SACH (solid ankle, cushioned heel) foot.

Balk and colleagues (2018) published the results of a comparative effectiveness review of lower limb prostheses and what factors best determine the prosthetic configuration that is optimal for an individual with an amputation. The authors reviewed assessment techniques, prediction tools, and functional outcome measurement tools through 80 eligible studies with a focus on tools that are generalizable to the Medicare population. For all outcomes evaluated, the authors concluded that there is low or insufficient evidence. The studies that were available had methodological limitations, inconsistent findings, and few studies reported outcomes of interest. There is insufficient evidence to predict success and added benefit from a specific prosthesis, including components and configuration, for subgroups of amputees. Furthermore, no assessment instruments have been identified that reliably predict individual success based on prosthesis configuration.

In 2025 the Veteran’s Affairs and Department of Defense (VA/DoD) published their clinical practice guideline for rehabilitation of individuals with lower limb amputation. This document provides guidance on prosthesis selection and states the following:

These studies represent very low strength of evidence and are insufficient evidence to prescribe any specific transfemoral socket design or to recommend for or against ischial containment or sub-ischial socket designs in community ambulators.

Additionally, they recommend full consideration of the individual’s health status when relevant to prosthetic use outcomes:

14. We suggest screening for factors associated with rehabilitation outcomes following acquired limb loss, (e.g., smoking, comorbid injuries or illnesses, psychosocial characteristics and physical function).

In 2017, CMS published a health technology assessment titled Lower Limb Prosthetic Workgroup Consensus Document. That document recommended the following factors be included in a pre-authorization for lower limb prostheses:

History

• Name
• *Age
• *Age at limb loss
• *Level of amputation
• *Etiology of amputation
• *Co-morbidities of the patient and medical readiness related to safe use of a prosthesis
• *Emotional readiness of the patient
• *Cognitive abilities of the patient related to safe use of a prosthesis
• Current or past therapy applicable to amputation (if appropriate)
• Prior level of functioning
• Current level of functioning (including use of prosthesis and assistive devices, if applicable)
• Patient goals
  • Short term
  • Long term
• Patient social situation information
  • Type of residence (e.g., private home, nursing facility or assistive living)
  • Need /availability of caregiver (if required)
• Architecture of home
  • Architecture of home (e.g., required steps to entrance/kitchen/bathroom/bedroom)

Physical Exam

• *General description of cardiopulmonary status
• *General description of bilateral lower limbs (e.g., scars, neuromas, wounds, edema, skin quality)
• *Specific description of limb to receive prosthesis (e.g., length, shape, incision site, overall readiness for prosthesis
• Range of motion and strength (bilateral as appropriate):
  • Hip
  • Knee
  • Ankle
• Sensation (bilateral)
• Proprioception (bilateral)
• General description of upper limb range of motion and strength
• Description of sitting and (if appropriate) standing balance
• Description (if appropriate) of transfer and ambulation abilities (include description of balance and mobility aids uses)

Additionally, the document states that repairs and replacements to a prosthesis are governed by 1834 of the Social Security Act, which states the following:

(G) Replacement of prosthetic devices and parts.—
(i) In general.—Payment shall be made for the replacement of prosthetic devices which are artificial limbs, or for the replacement of any part of such devices, without regard to continuous use or useful lifetime restrictions if an ordering physician determines that the provision of a replacement device, or a replacement part of such a device, is necessary because of any of the following:
(I) A change in the physiological condition of the patient.
(II) An irreparable change in the condition of the device, or in a part of the device.
(III) The condition of the device, or the part of the device, requires repairs and the cost of such repairs would be more than 60 percent of the cost of a replacement device, or, as the case may be, of the part being replaced. (ii) Confirmation may be required if device or part being replaced is less than 3 years old.—If a physician determines that a replacement device, or a replacement part, is necessary pursuant to clause (i)—
(I) such determination shall be controlling; and (II) such replacement device or part shall be deemed to be reasonable and necessary for purposes of section 1862(a)(1)(A); except that if the device, or part, being replaced is less than 3 years old (calculated from the date on which the beneficiary began to use the device or part), the Secretary may also require confirmation of necessity of the replacement device or replacement part, as the case may be.

Some prosthetics and prosthetic accessories are designed specifically for use during leisure or sporting activities such as running, biking, or swimming. Such devices provide functionality above what may be considered necessary for routine daily activities for an individual or may be beyond what may be considered clinically appropriate for an individual. The use of a prosthetic device designed and intended specifically for use during leisure or sporting activities does not primarily serve a medical purpose. That use is thus considered not medically necessary.

Overall, the available evidence for the selection of prosthetic devices is poor, and the available recommendations emphasize a holistic approach taking multiple factors into consideration, including the individual’s health and functional status, as well as potential functional abilities and use.

Peer Reviewed Publications:

1. Hofstad C, Linde H, Limbeek J, Postema K. Prescription of prosthetic ankle-foot mechanisms after lower limb amputation. Cochrane Database Syst Rev. 2004;(1):CD003978.
2. Lovegreen W, Murphy DP, Smith WK, et al. Lower Limb Amputation and Gait. In: Cifu DX ed, Braddom's Physical Medicine and Rehabilitation, 5th Ed. Philadelphia, PA: Elsevier, 2016: 191-223.

Government Agency, Medical Society, and Other Authoritative Publications:

1. Balk EM, Gazula A, Markozannes G, et al. Comparative Effectiveness Review Number 213. Lower limb prostheses: measurement instruments, comparison of component effects by subgroups, and long-term outcomes. Agency for Healthcare Research and Quality. 2018 September. Available at: https://effectivehealthcare.ahrq.gov/sites/default/files/related_files/cer-213-lower-limb-protheses-report.pdf. . Accessed on August 4, 2026. 
2. Centers for Medicare & Medicaid Services. Activities of Daily Living. 2008. Available at: https://www.cms.gov/research-statistics-data-and-systems/research/mcbs/downloads/2008_appendix_b.pdf. Accessed on August 4, 2026.
3. Centers for Medicare & Medicaid Services. Health Technology Assessment. Lower Limb Prosthetic Workgroup. Consensus Document. September 2017. Available at: https://www.cms.gov/Medicare/
   Coverage/DeterminationProcess/downloads/LLP_Consensus_Document.pdf. Accessed August 4, 2026.
4. Veteran’s Affairs/ Department of Defense. VA/DoD Clinical Practice Guideline for Rehabilitation of Individuals with Lower Limb Amputation. 2025. Available at: https://www.healthquality.va.gov/guidelines/rehab/amp/. Accessed on August 4, 2026.

Lower Leg
Prosthesi
SACH Foot

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