Traditional Medicare or Medicare Advantage: what the authorization path looks like for prosthetics

Medicare is not one program. It is a set of coverage pathways that go by the same name, and which one you’re in matters for how prosthetic access actually works — not in the abstract, but in the sequencing of steps, the providers available to you, and the days or weeks the process can add.

This is worth understanding before a device is on the table, because the authorization path under traditional Medicare Part B and the path under a Medicare Advantage plan operate by different rules. They produce the same coverage in theory. They produce meaningfully different experiences in practice.

The two versions of Medicare

Traditional Medicare — often called Part A and Part B — is the federal program run directly by CMS. Part A covers inpatient hospital and skilled nursing; Part B covers outpatient services including prosthetics, which are classified as durable medical equipment under the DMEPOS framework.

Medicare Advantage (Part C) is private insurance that contracts with Medicare to deliver your benefits. When you’re enrolled in a Medicare Advantage plan, you receive at minimum everything traditional Medicare covers, but the coverage is administered by the insurer rather than CMS. The insurer can add requirements — prior authorization, network restrictions, additional documentation — as long as those requirements don’t result in less coverage than traditional Medicare provides.

The line on paper (same coverage) and the line in practice (same authorization process) are not the same line.

How traditional Part B handles prosthetics

Under traditional Medicare Part B, prosthetics are covered without a pre-approval step. There is no prior authorization requirement for lower-limb prostheses under traditional Medicare.

What there is, instead, is a documentation requirement that the claim must satisfy at the time it is submitted. The prescribing practitioner writes a clinical order. The prosthetist prepares documentation — functional assessment, medical necessity notes, K-level support, component coding — and submits a claim to the appropriate Medicare Administrative Contractor (Novitas Solutions or CGS Administrators, depending on geography). The contractor reviews the claim and either pays or audits.

This does not mean the process is instant or easy. Documentation that does not satisfy the Lower Limb Prostheses Local Coverage Determination (LCD L33944) or the policy article in effect at the time of the claim can result in a denial. Audits are retrospective, meaning the device may be delivered and then challenged months later. But there is no authorization step between clinical evaluation and fitting — the coverage criteria run alongside the clinical process, not in front of it.

For provider access: under traditional Part B, you can receive care from any DMEPOS supplier enrolled with Medicare who accepts Medicare assignment. There is no network.

How Medicare Advantage handles prosthetics

Medicare Advantage plans are required to cover prosthetics because traditional Medicare covers prosthetics. But the manner of that coverage is the insurer’s to design, within CMS limits.

In practice, most Medicare Advantage plans require prior authorization for prosthetics — particularly for higher-cost components, custom fabricated devices, and microprocessor-controlled systems. This means the request must be submitted and approved before fitting can occur. The plan’s medical director or clinical review team determines whether the requested device meets coverage criteria.

Two additional constraints apply under most MA plans:

Network. You must use an in-network O&P provider. The plan’s network may or may not include the clinic you prefer, may or may not include providers in your area who specialize in your type of amputation or activity level, and can change at the annual plan renewal. A prosthetist who was in-network when you started a fitting process may be out-of-network by the time you need a replacement component.

Coverage criteria. MA plans are required to use coverage criteria that are consistent with traditional Medicare — they cannot impose additional clinical barriers that would result in covering fewer prosthetics than Part B covers. CMS tightened this rule in 2024, requiring MA plans to align prior authorization policies with traditional Medicare coverage criteria and to make those policies publicly available. In practice, “consistent with” is interpreted and applied by individual plan reviewers, and the appeals process for a denied prior authorization is specific to each plan.

What prior authorization adds to the timeline

Under traditional Medicare, the authorization question is not a separate step — it runs in parallel with clinical work and is resolved at the claim submission stage. The prosthetist manages it on the back end.

Under Medicare Advantage, prior authorization is a sequential step. The typical process looks something like this:

1. Clinical evaluation and prescription
2. Prosthetist submits prior authorization request, with supporting documentation
3. Plan reviews and responds (standard review: up to 14 calendar days; expedited review, when medical urgency is established: 72 hours)
4. Authorization granted, modified, or denied
5. Fitting proceeds if authorized; appeal process begins if denied
6. Delivery, follow-up

Federal rules establish the 14-day / 72-hour response windows. In practice, plans sometimes take the full window; peer-to-peer calls between the prosthetist or prescribing practitioner and the plan’s clinical reviewer can speed things along but require provider time and coordination. A denial that goes to appeal extends the timeline further — peer-to-peer requests, internal appeal, then external review if needed.

None of this is unique to prosthetics; prior authorization affects access to all kinds of specialized care under Medicare Advantage. But prosthetic fitting has particular timing sensitivities. Residual limb volume changes throughout recovery. A delayed fitting doesn’t just push back the date — it can mean returning to evaluation and documentation when the clinical picture has shifted.

What changed under the 2022–2024 federal reforms

The Improving Seniors’ Timely Access to Care Act (ISTAICA), enacted in October 2022, directed CMS to address prior authorization practices under Medicare Advantage. CMS implemented rules in 2024 that included:

• Requiring MA plans to make their prior authorization criteria publicly available, so providers and patients can see the basis for decisions before submitting requests
• Requiring plans to accept electronic prior authorization requests, reducing administrative friction
• Requiring that prior authorization decisions align with clinical criteria consistent with traditional Medicare, and that denials identify which coverage criterion was not met
• Strengthening continuity-of-care protections when a patient changes plans or a provider leaves the network mid-course of treatment

These rules reduced some of the opacity in the prior authorization process. They did not eliminate prior authorization requirements from Medicare Advantage plans, and they did not equalize the authorization experience between Part B and Part C. What they did was establish clearer procedural minimums and more enforceable transparency requirements.

If you receive a prior authorization denial from a Medicare Advantage plan, the denial must now tell you specifically which criterion was not met. That matters for appeals: a denial that identifies the documentation gap gives you — and your O&P clinic — something specific to address.

If you’re comparing plans or switching between them

Medicare Advantage open enrollment runs each fall for the following calendar year. For people evaluating plans while already on a device or anticipating care, a few factors are worth checking specifically:

• Does the plan’s network include O&P providers in your area? Network directories change, and they are sometimes out of date. Call the clinic directly to confirm in-network status with a specific plan before enrolling.
• What are the plan’s prior authorization requirements for prosthetics? Since 2024, this information must be publicly posted. If you cannot find it, the plan’s member services line is required to explain it.
• Does the plan have continuity-of-care protections if you are mid-fitting? Mid-year plan switching is limited, but coverage changes at the January 1 renewal date. If you are in a fitting process that runs across a plan year, confirm whether the new plan will honor an in-progress authorization from the prior plan.

People who return to traditional Medicare from Medicare Advantage (switching back is permitted under certain conditions and during open enrollment periods) generally regain the any-licensed-provider access and no-prior-authorization structure for prosthetics under Part B. Medigap supplemental coverage, if available and elected, can cover Part B cost-sharing — the 20 percent coinsurance after the deductible that traditional Medicare does not waive.

Questions to bring to your clinic and your plan

Your O&P clinic’s billing coordinator has almost certainly worked with your specific Medicare Advantage plan before. They know which codes the plan tends to flag for prior authorization, how responsive the plan’s clinical review team is, and what documentation tends to support or undermine an approval. Asking them about the prior authorization process for your plan before the clinical evaluation starts can save time.

Questions worth asking your plan:

• Is prior authorization required for the device or component being requested?
• What clinical documentation does the plan require in the prior authorization submission?
• What is the plan’s response timeline for this type of request?
• If a request is denied, what is the first level of appeal and who initiates it?

Questions worth asking your clinic:

• Has your billing team worked with this plan before, and do you know their prior authorization process?
• What documentation will you need from my prescribing practitioner to support the submission?
• If the authorization is delayed, is there anything the patient can do on our end to help?

The answers vary by plan and by clinic. Getting them early in the process costs nothing and can materially affect how the authorization goes.

---

Amputee News does not provide individualized medical, legal, benefits, or insurance advice. Medicare coverage, prior authorization requirements, and Medicare Advantage plan rules vary by plan, geography, and individual circumstances. Coverage rules can change at open enrollment or when CMS updates program requirements. For questions about your specific coverage or a prior authorization denial, contact your O&P clinic’s billing team, your prescribing practitioner, or your plan’s member services. Medicare.gov maintains current information on coverage and plan comparison tools.