Microprocessor-Controlled Prostheses for the Lower Limb
Customize your policy alerts
Sign up for Blue Cross Blue Shield - Massachusetts Policy 133 alerts
Get alerted when Policy 133 changes without checking for updates manually.
Monitor payer policy activity
Policy governing medical necessity, prior authorization, and coding for microprocessor-controlled knee prostheses and related lower-limb microprocessor or powered components for commercial members of Blue Cross Blue Shield - Massachusetts.
No material clinical or coverage changes in this revision.
Coverage and Medical Necessity Criteria
Medical necessity for microprocessor-controlled knee
Covered when ALL of the following are met
A need for daily ambulation of at least 400 continuous yards, daily and frequent ambulation at variable cadence or on uneven terrain, and/or daily and frequent use of ramps/stairs; typically need 2 or more of these activities to show benefit.
Contraindications / Patient selection limits
Contraindications / not appropriate when ANY of the following are present
Additional selection guidance
Other indications/considerations
Coverage summary by device and amputation level
Coverage stance summarized from evidence sections
Based on within-subject comparisons and systematic reviews
Benefit may be incremental
Insufficient evidence
Insufficient evidence
A microprocessor-controlled knee, a powered knee, and microprocessor-controlled or powered foot are considered investigational when the individual does not meet the selection and identification criteria described in this policy, including functional level, ability to fit a socket, wound stability, and sufficient physical and cognitive capacity to use the device.
There is insufficient evidence to conclude that powered knees or microprocessor-controlled or powered ankle-foot prostheses improve net health outcomes. For transfemoral powered knees, no data are available. For microprocessor-controlled or powered ankle-foot prostheses in tibial (transtibial) amputees, the limited evidence does not show improved functional outcomes compared with standard prostheses (one small study reported some quality-of-life benefit); overall the evidence is inadequate to determine meaningful clinical improvement.
A microprocessor-controlled knee is considered investigational if the individual does not meet the policy’s selection and identification criteria (for example, inadequate functional level, inability to tolerate socket wear, unstable wound, insufficient cardiovascular/pulmonary reserve, or limited cognitive ability). A powered knee is considered investigational irrespective of meeting those criteria given the lack of evidence supporting clinical benefit.
Use of powered knees and of microprocessor-controlled or powered ankle-foot prostheses for transtibial (tibial) amputees is considered to have insufficient evidence to demonstrate improvement in net health outcome and therefore is not supported as proven effective by the evidence summarized in this policy.
Billing Codes and Key Parameters
| L5615 | Addition, endoskeletal knee-shin system, 4 bar linkage or multiaxial, fluid swing and stance phase control |
| L5856 | Addition to lower extremity prosthesis, endoskeletal knee-shin system, microprocessor control feature, swing and stance phase, includes electronic sensor(s), any type |
| L5857 | Addition to lower extremity prosthesis, endoskeletal knee-shin system, microprocessor control feature, swing phase only, includes electronic sensor(s), any type |
| L5858 | Addition to lower extremity prosthesis, endoskeletal knee shin system, microprocessor control feature, stance phase only, includes electronic sensor(s), any type |
| L2221 | Addition to lower extremity orthosis, ankle system, microprocessor-controlled feature plantarflexion and/or dorsiflexion, includes power source |
| L5969 | Addition, endoskeletal ankle-foot or ankle system, power assist, includes any type motor(s) |
| L5973 | Endoskeletal ankle foot system, microprocessor controlled feature, dorsiflexion and/or plantar flexion control, includes power source |
| L5992 | All lower extremity prosthesis, foot shell for modular foot/non-solid ankle cushion heel (sach) replacement only |
| F07Z9CZ | Gait Training/Functional Ambulation Treatment using Mechanical Equipment |
| F07Z9DZ | Gait Training/Functional Ambulation Treatment using Electrotherapeutic Equipment |
| F07Z9EZ | Gait Training/Functional Ambulation Treatment using Electrotherapeutic Equipment Gait Training/Functional Ambulation Treatment using Orthosis |
| F07Z9UZ | Gait Training/Functional Ambulation Treatment using Prosthesis |
| F07Z9YZ | Gait Training/Functional Ambulation Treatment using Other Equipment |
| F07Z9ZZ | Gait Training/Functional Ambulation Treatment |
| F0DZ6EZ | Dynamic Orthosis Device Fitting using Orthosis |
| F0DZ6FZ | Dynamic Orthosis Device Fitting using Assistive, Adaptive, Supportive or Protective Equipment |
| F0DZ6UZ | Dynamic Orthosis Device Fitting using Prosthesis |
| F0DZ6ZZ | Dynamic Orthosis Device Fitting |
| L2221 | Addition to lower extremity orthosis, ankle system, microprocessor-controlled feature plantarflexion and/or dorsiflexion, includes power source. |
| L5969 | Addition, endoskeletal ankle-foot or ankle system, power assist, includes any type motor(s). |
| L5973 | Endoskeletal ankle foot system, microprocessor controlled feature, dorsiflexion and/or plantar flexion control, includes power source. |
| L5992 | All lower extremity prosthesis, foot shell for modular foot/non-solid ankle cushion heel (sach) replacement only |
Authorization, Documentation, and Submission Requirements
Prior authorization required for commercial members (inpatient & outpatient)
Prior authorization (precertification) is required for services described in this policy for commercial members when performed inpatient or outpatient; submit requests via Authorization Manager and ensure requests meet medical policy guidelines.
- Applies to inpatient services: "precertification/preauthorization IS REQUIRED if the procedure is performed inpatient."
- Applies to outpatient commercial PPO: "Prior authorization is required."
- Requests must meet medical policy guidelines when submitted for commercial members.
Prior authorization required for commercial products — updates & coding clarifications
Prior authorization is required for commercial products and coding clarifications have been made in multiple policy updates; providers should submit prior authorization requests per the payer's Authorization Manager/process.
- Policy history documents repeated clarifications to prior authorization and coding (multiple entries noting clarified coding information and prior authorization clarification for PPO plans).
- Authorization Manager is the submission channel for initial requests.
Fit a standard prosthesis first when benefit is uncertain
For individuals with uncertain potential benefit, fit a standard (non-microprocessor) prosthesis first to determine function before providing a microprocessor-controlled knee.
- Policy: "For individuals in whom the potential benefits of the microprocessor knees are uncertain, individuals may first be fitted with a standard prosthesis to determine their level of function with the standard device."
Use Authorization Manager and follow submission requirements
Providers must follow the policy's authorization and documentation requirements when requesting services; use Authorization Manager and include all required identifiers so requests are processed accurately.
- Enter the facility's NPI or provider ID for where services are performed and the servicing provider's NPI/provider ID (servicing provider, not billing group).
- Consult policy history and guidance for submission processes and coding clarifications.
Submit initial authorization requests via Authorization Manager with facility and servicing provider NPIs
Submit initial authorization requests using Authorization Manager and include the facility NPI/provider ID and the servicing provider's NPI/provider ID to ensure accurate processing.
- Authorization Manager is available 24/7 and is the recommended method to request authorizations, submit clinical documentation, and check case status.
- Enter the servicing surgeon's NPI or provider ID as the servicing provider (not the billing group).
Where to find submission and documentation guidance
Consult the policy's referenced guidance for details on managed care submission rules, indemnity/PPO guidelines, clinical exception processes, and medical technology assessment requirements when preparing documentation.
- Policy history and "Information Pertaining to All Blue Cross Blue Shield Medical Policies" list Managed Care Guidelines, Indemnity/PPO Guidelines, Clinical Exception Process, and Medical Technology Assessment Guidelines as resources.
Denial risk if precertification/prior authorization is not obtained
Failure to obtain precertification/preauthorization for services described in this policy when required for commercial members may result in denial of the claim or reduction of benefits.
- Inpatient services: precertification/preauthorization is required and lack of it may lead to denial.
- Outpatient commercial PPO: prior authorization is required; failure to obtain it risks denial.
Prior authorization requirement history — in place since at least 2009
Prior authorization for commercial products has been required since at least 2009 and the policy history documents multiple updates clarifying prior authorization and coding information.
- Policy history entries span from 2015 through 4/2026 and note repeated clarifications to prior authorization procedures and coding information.
- Explicit statement: prior authorization information clarified for PPO plans (effective 6/1/2022) and earlier entries referencing prior authorization requirements.
Background and Rationale
Microprocessor-controlled knees are prosthetic knee joints that use sensors and a microprocessor to modulate swing and/or stance phase mechanics in real time with the intention of improving gait stability, reducing falls, enabling variable-cadence ambulation (including ramp and hill negotiation), and improving overall function. The evidence shows objective functional improvements and strong patient preference for microprocessor knees in K3 and K4 transfemoral amputees, and a potential incremental benefit for some K2 ambulators when stance stability permits advancement. Candidate selection depends on functional level and on sufficient cardiovascular/pulmonary reserve, strength, balance, cognitive ability, and the ability to fit and tolerate a socket.
Key Definitions and Terms
Policy Revision History
Policy updated with literature review through January 20, 2026; references added and coding information clarified; policy statements unchanged.
Clarified coding information; annual policy review with references updated; policy statements unchanged.
Annual policy review; references updated; policy statements unchanged.
Annual policy review; references updated and coding information clarified; policy statements unchanged.
Policy clarified to include prior authorization requests using Authorization Manager.
Annual policy review with minor editorial refinements to policy statements; intent clarified.
Prior authorization information clarified for PPO plans; effective 6/1/2022.
Annual policy review; description, summary, and references updated; policy statements unchanged.
Annual policy review; policy statements unchanged.
Clarified coding information.
Local and national coverage determination references added; annual policy review with description, summary, and references updated; policy statements unchanged.
Annual policy review; description, summary, and references updated; policy statements unchanged.
Annual policy review; background and summary clarified; policy statements unchanged.
Coding information clarified.
Annual policy review; patient selection and identification guidelines aligned with national policy, effective 11/1/2016.
Clarified coding information and aligned guideline with national policy, effective 11/1/2016.
OpenPayer is powered by Trek Health's payer performance platform. Trek continuously ingests, validates, and normalizes Transparency in Coverage data alongside payer policies and other commercial payer data to create a structured payer intelligence foundation. OpenPayer uses this foundation to deliver personalized search results, dynamically generated policy pages, and tailored policy monitoring based on each user's payers, specialties, billing codes, and areas of interest. The same intelligence powers broader payer performance workflows, including reimbursement benchmarking, contract evaluation, payer negotiations, and financial decision-making.