Glossary · Billing

Prior authorization

Prior authorization (PA) is a payer requirement that a provider obtain approval before delivering a specific service, procedure, or item—otherwise the claim will be denied regardless of medical necessity. Approval is granted when submitted clinical documentation meets the payer's coverage criteria.

Verified May 8, 2026 · 7 sources ↓

Drawn from CMSRacmonitorMedicotechllcAdsc

Definition

Source · Editorial summary grounded in 7 cited references ↓

Prior authorization is a utilization-management tool used by Medicare Advantage plans, Medicaid managed care organizations, CHIP plans, Qualified Health Plans, and most commercial insurers to evaluate whether a proposed service meets coverage criteria before it is rendered. The provider submits clinical documentation—diagnosis codes, treatment history, functional status, imaging findings, and failed-conservative-therapy records—and the payer issues a provisional decision to approve, deny, or request additional information. Approval does not guarantee payment; the submitted claim must still match the authorized service in procedure code, date of service, place of service, and performing provider.

In orthopedics, prior authorization is routinely required for high-cost elective procedures (total joint arthroplasty, spinal fusion, arthroscopy), advanced imaging (MRI, CT), durable medical equipment (custom knee and spinal braces under HCPCS codes L0648, L0650, L1833, L1851), and certain hospital outpatient department services under CMS's mandatory PA program. CMS also runs a separate PA program for specific DMEPOS items and selected hospital outpatient department procedures, requiring prospective approval before a Medicare fee-for-service claim can be paid.

As of January 1, 2026, the CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F) shortened decision timelines for Medicare Advantage, Medicaid, CHIP, and exchange plans: standard decisions must be issued within 7 calendar days, expedited (urgent) decisions within 72 hours, and denials must include a specific reason rather than a generic rejection code. These changes apply to non-drug services; drug PA is governed separately under a pending rule. Electronic PA infrastructure via FHIR APIs is required but compliance dates were extended to January 2027 for most payers.

Why it matters

A missing or mismatched prior authorization is one of the leading causes of orthopedic claim denials and post-payment recoupment. If the approved CPT code, place of service, or performing provider differs from what was billed, the payer can deny or claw back the entire payment even when care was clinically appropriate. Inadequate documentation at the time of PA submission—such as recording 'knee pain' without documenting failed physical therapy, conservative medication use, and functional limitation—triggers auto-denials from payer machine-learning algorithms before a human reviewer ever sees the case. Because the 2026 CMS rule now requires payers to cite a specific denial reason, providers who lose a PA appeal on documentation grounds have a clear and documented gap they must fix before resubmitting.

Common mistakes

Where people most often go wrong with this concept.

Source · Editorial brief grounded in cited references ↓

Submitting a PA for a CPT code that does not match the CPT code ultimately billed—approval for 27447 (total knee arthroplasty) does not cover 27446 (hemiarthroplasty) if the intraoperative plan changes.
Failing to document failed conservative therapy before requesting PA for joint arthroplasty, spinal injections, or hyaluronic acid injections—payers require evidence of prior treatment failure, not just a diagnosis.
Treating PA approval as a guarantee of payment without verifying that the approved service, date of service, and performing provider match the submitted claim exactly.
Using a generic diagnosis such as 'lumbar pain' (M54.50) on the PA request instead of the specific, highest-specificity ICD-10-CM code that reflects severity and laterality—algorithmic reviewers score specificity.
Missing the authorization expiration date and rendering the authorized service after the approval window closes, which voids the authorization and results in denial.
Assuming that Original Medicare fee-for-service does not require PA—CMS does require PA for specific hospital outpatient department services and certain DMEPOS items including select spinal and knee braces.
Not requesting expedited review when clinical urgency warrants it—using the standard 7-day window when the patient's condition could deteriorate delays care and may result in a worse clinical outcome.
Omitting modifier ST on DMEPOS claims when a brace is furnished urgently during an office visit, which routes the claim into the wrong review pathway and increases prepayment review scrutiny.

Related codes

Codes commonly involved when this concept appears in practice.

CPT

ICD-10

M17.11 M17.12 M16.11 M16.12 M54.50

Modifiers

KX Medical-policy requirements met 59 Distinct procedural service

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 7 cited references ↓

01Does Original Medicare (fee-for-service) require prior authorization for orthopedic surgery?

Original Medicare fee-for-service does not require PA for most orthopedic surgeries, but CMS does require PA for specific hospital outpatient department services and certain DMEPOS items—including select spinal and knee braces under HCPCS codes L0648, L0650, L1833, and L1851. Medicare Advantage plans set their own PA requirements and frequently require PA for joint arthroplasty, spinal procedures, and advanced imaging.

02What happens if I render a service after the prior authorization expires?

The payer will deny the claim. Authorization windows are date-specific; a service rendered even one day after the expiration date is treated as unauthorized. You must request a new authorization or an extension before delivering the service.

03How did the 2026 CMS rule change the prior authorization process?

The CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F), effective January 1, 2026, requires Medicare Advantage, Medicaid managed care, CHIP managed care, and exchange plans to issue standard PA decisions within 7 calendar days and expedited decisions within 72 hours. Denials must now include a specific reason. These requirements do not apply to drugs, which are governed under a separate proposed rule.

04If the payer approves my PA request but the intraoperative findings require a different procedure, do I need a new authorization?

Yes. The authorization is specific to the approved CPT code. If intraoperative findings require a procedure that maps to a different CPT code—even a closely related one—you should contact the payer as soon as possible. Billing a CPT code that was not authorized results in denial and potential recoupment.

05What documentation most commonly causes PA denials in orthopedics?

The most common documentation gap is failure to establish failed conservative therapy. Payers—particularly those using algorithmic review—require explicit documentation that specific conservative treatments (physical therapy, NSAIDs, injections) were tried for an adequate duration and failed. A diagnosis alone, without this history, is insufficient.

06Is a prior authorization the same as a predetermination?

No. A predetermination is a voluntary, non-binding estimate of whether a service would be covered if rendered; it does not authorize care. A prior authorization is a required payer approval that must be obtained before the service is rendered for the claim to be paid.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

Mira AI Scribe

Mira flags procedures and DMEPOS items that commonly require prior authorization based on the payer, CPT code, and place of service identified in the encounter. When a PA-required service is detected, Mira prompts the clinician to document the elements payers most frequently cite as the basis for auto-denial: (1) specific diagnosis with laterality and severity at the highest ICD-10-CM specificity available; (2) duration and type of conservative treatments attempted; (3) objective evidence of treatment failure or functional decline (e.g., validated outcome scores, imaging findings, range-of-motion measurements); and (4) clinical rationale explaining why the proposed procedure is the appropriate next step. For total joint arthroplasty, Mira surfaces a structured PA documentation checklist aligned with common payer criteria—including documented failure of physical therapy, anti-inflammatory medications, and corticosteroid injections, plus functional limitation language tied to activities of daily living. For DMEPOS items such as custom knee braces (L1833, L1851) or spinal orthoses (L0648, L0650), Mira flags whether the ST modifier is appropriate based on the clinical context recorded in the note. Mira also cross-checks the CPT code selected at charge capture against the CPT code submitted on the PA request and alerts the coder to any mismatch before claim submission. PA expiration dates captured during intake are surfaced as alerts if the date of service approaches or exceeds the authorization window.

See Mira's approach

Related terms

Medical necessity Compliance

Medical necessity is the standard requiring that a service or item be reasonable and appropriate for diagnosing or treating a patient's condition according to accepted clinical practice. Payers—including Medicare—use this standard to determine whether a claim will be covered and paid.

Predetermination of benefits Billing

Predetermination of benefits is a voluntary, pre-service review in which a provider submits procedure and diagnosis information to a payer before treatment so the payer can estimate coverage and patient liability—without guaranteeing payment. It is not the same as prior authorization, and approval at this stage does not obligate the payer to pay the final claim.

Place of service (POS) Coding

A two-digit code reported on every line of a professional claim (CMS-1500 / 837P) that identifies where the patient physically received the service. POS directly controls whether CMS pays the facility or non-facility rate and is required under HIPAA's standard transaction rules.

Advance Beneficiary Notice (ABN) Billing

An Advance Beneficiary Notice of Noncoverage (ABN) is a written notice providers and suppliers must deliver to Original Medicare (Part B) beneficiaries before furnishing an item or service that Medicare is expected to deny, transferring potential financial liability to the patient when properly executed.