HCPCS Code L4397: Static or Dynamic Ankle Foot Orthosis Guide

Key Takeaways

HCPCS Code L4397 describes a prefabricated, off-the-shelf static or dynamic ankle-foot orthosis with soft interface material, adjustable for fit and positioning.

L4396 and L4397 share the same long descriptor (including the phrase “adjustable for fit”). The only differentiator is fitting method: L4396 = custom fitted by a qualified individual; L4397 = off-the-shelf, requiring only minimal self-adjustment.

Medicare covers L4396/L4397 under LCD L33686 only when criteria 1-4 are all met (nonfixed plantar flexion contracture with at least 10 degrees of dorsiflexion on goniometer testing) OR criterion 5 (plantar fasciitis) is met.

Modifier KX is required when all LCD coverage criteria are documented; append GA when criteria are not met and an ABN has been issued. Medicare does not reimburse L4398, the foot drop recumbent positioning splint.

HCPCS Code L4397: Definition and Clinical Description

DME suppliers billing ankle-foot orthoses to Medicare face one of the most documentation-intensive HCPCS categories in musculoskeletal billing. A single missing modifier or an unsupported diagnosis code is enough to trigger a denial that can take months to appeal. HCPCS Code L4397 covers one specific product category within this family, and understanding exactly what it does and does not cover is the starting point for clean claims.

The official descriptor for HCPCS Code L4397 reads: Static or dynamic ankle foot orthosis, including soft interface material, adjustable for fit, for positioning, may be used for minimal ambulation, prefabricated, off-the-shelf. According to the Centers for Medicare and Medicaid Services (CMS) HCPCS Level II coding system, this code applies only to prefabricated, off-the-shelf (OTS) devices. Custom-fabricated AFOs are classified under different L-codes entirely.

Three product characteristics must all be present for L4397 to apply correctly. First, the device must be prefabricated, meaning it is produced in bulk and not constructed from a cast or direct model of the patient’s limb. Second, it must be off-the-shelf, meaning it can be dispensed directly from existing stock with only minimal self-adjustment that does not require a qualified practitioner’s expertise. Third, it must include soft interface material and be adjustable for fit. A rigid non-padded night splint without adjustable strapping components would fall outside this descriptor.

Positioning Use vs. Ambulatory Use

The phrase “for positioning, may be used for minimal ambulation” is central to correct code selection. CMS LCD L33686 classifies L4396 and L4397 together under the heading “AFOs NOT USED DURING AMBULATION.” This means the primary clinical purpose is positioning the ankle and foot while the patient is non-weight-bearing, typically during rest or sleep. Minimal ambulation (such as walking to the bathroom) is permitted but is not the therapeutic goal.

Ambulatory-use AFOs, worn during walking or standing to correct gait, fall under a separate set of HCPCS codes. Billing an ambulatory-use AFO under L4397 misrepresents the product and constitutes a coding error. Claims management software that flags code-to-product mismatches at the time of order entry can prevent this error before the claim is submitted.

Medicare Coverage Criteria for HCPCS Code L4397 Under LCD L33686

Medicare covers HCPCS Code L4397 only when coverage criteria under CMS Local Coverage Determination (LCD) L33686 are satisfied. Coverage requires that either all of criteria 1-4 are met, or criterion 5 alone is met. Supplying the device before these criteria are confirmed and documented is the most common reason for post-payment audit recoupment.

Criteria 1-4 (All Must Be Met)

• Criterion 1: The beneficiary has a plantar flexion contracture of the ankle with dorsiflexion on passive range of motion testing of at least 10 degrees (i.e., a nonfixed contracture).
• Criterion 2: There is reasonable expectation of the ability to correct the contracture.
• Criterion 3: The contracture is interfering or expected to interfere significantly with the beneficiary’s functional abilities.
• Criterion 4: The orthosis is used as a component of a therapy program which includes active stretching of the involved muscles and/or tendons.

Pre-treatment passive range of motion must be measured with a goniometer and the value documented in the medical record. Without a goniometric measurement on file, the supplier cannot demonstrate that criterion 1 is satisfied, and DME MAC reviewers will deny the claim on documentation grounds.

Criterion 5 (Standalone)

Criterion 5 is met when the beneficiary has plantar fasciitis. The covered diagnoses for this pathway are listed in Group 1 of CMS Policy Article A52457. When criterion 5 applies, suppliers do not need to document criteria 1-4; the plantar fasciitis diagnosis itself supports medical necessity for a positioning AFO under LCD L33686. For physical therapy practices and orthotists working with podiatry referrals, criterion 5 is the most common pathway for night splint billing.

Two denial scenarios are explicit in the policy. L4396/L4397 will be denied as not reasonable and necessary if the contracture is fixed (no measurable dorsiflexion on passive range of motion testing). They will also be denied for a beneficiary with foot drop in the absence of an ankle plantar flexion contracture; foot drop alone, without a documented contracture, does not meet LCD L33686 criteria.

ICD-10 Diagnosis Codes That Support HCPCS Code L4397

CMS Policy Article A52457 requires suppliers to include diagnosis codes on the claim line for HCPCS codes L4396, L4397, L4392, and L4631. The ICD-10 codes below represent the most commonly used diagnoses for L4397 billing. Always cross-reference the current policy article, as the code list is updated with each annual CMS revision cycle.

Laterality matters. When billing for a right-foot device, use right-laterality ICD-10 codes where available (e.g., M77.31 for right calcaneal spur). When both feet are treated simultaneously, two separate claim lines may be required with RT and LT modifiers applied. Accurate ICD-10 code documentation at the time of order, not retrospectively added at billing, is what DME MAC reviewers look for during audits.

Modifier Usage for HCPCS Code L4397 Claims

Modifiers are not optional extras for HCPCS Code L4397 Medicare claims. Missing or incorrect modifiers are among the top reasons DME claims are denied or flagged for review. The four modifiers most relevant to L4397 billing each serve a distinct function, and confusing them creates significant compliance exposure.

• Modifier KX: Appended when all coverage criteria in LCD L33686 are fully documented in the medical record. This modifier is a supplier’s attestation that the required documentation exists. It must never be added speculatively. If the documentation does not exist at the time of claim submission, KX is inappropriate.
• Modifier GA: Used when the supplier expects Medicare to deny the claim as not medically necessary, and an Advance Beneficiary Notice (ABN) has been issued and signed by the beneficiary. Without a valid ABN on file, billing GA exposes the supplier to liability for the denied charges.
• Modifier GZ: Appended when the item is expected to be denied as not medically necessary and no ABN has been issued. This signals to Medicare that the supplier expects denial and will not bill the beneficiary for the item. GZ and GA are mutually exclusive.
• Modifier RT / LT: Identifies which foot received the orthosis. RT (right side) or LT (left side) must be appended when bilateral devices are billed. Each foot is billed on a separate claim line.

Staying current with modifier policies is part of broader compliance requirements for orthotic and prosthetic suppliers. DME MAC contractors periodically update their guidance on modifier sequencing and documentation standards, so periodic policy reviews are essential for practices that bill L-codes regularly.

L4396 vs L4397: Key Differences and Code Selection

L4396 and L4397 share the same long descriptor and are grouped together under the same LCD coverage criteria. Both codes describe a “static or dynamic ankle foot orthosis, including soft interface material, adjustable for fit, for positioning, may be used for minimal ambulation, prefabricated.” The phrase “adjustable for fit” applies to both codes; it is not what differentiates them.

Per CMS coding guidelines, the differentiator is solely the fitting method, not any physical difference in the device itself:

• L4396 (prefabricated, custom fitted): The device requires substantial modification at the time of fitting. The supplier trims, bends, molds, assembles, or otherwise customizes the device to fit a specific patient, and that work requires the expertise of a certified orthotist or an individual who has equivalent training in customizing the item.
• L4397 (prefabricated, off-the-shelf): The device requires only minimal self-adjustment at the time of fitting. The adjustments needed (such as straps, hook-and-loop closures, or dial tensioning) do not require the expertise of a qualified practitioner and can be performed by the patient, caregiver, or any non-certified individual.

There is no physical difference between an L4396 and an L4397 device. The same product model can be billed under either code; the determining factor is the level of expertise required at the time of fitting. PDAC verification letters confirm which code applies to a particular product when dispensed under each fitting scenario. When in doubt, match the product’s PDAC verification letter to the HCPCS code used.

L4397 vs L4398

L4398 is a separate product type, not a replacement of L4397. The official descriptor for L4398 is Foot drop splint, recumbent positioning device, prefabricated, off-the-shelf. It is a recumbent (non-ambulatory) positioning splint designed specifically for foot drop, distinct from the static or dynamic AFO covered by L4396 and L4397.

Critically for billers: Medicare does not reimburse L4398. Per LCD L33686, foot drop splints (L4398) are denied as not reasonable and necessary. Suppliers should not bill Medicare for L4398 expecting reimbursement, and patients should be issued an ABN before dispensing if the device is provided. As the AAPC Codify HCPCS reference notes, the product description and billing code must reflect the actual transaction, and Medicare’s non-coverage of L4398 must be communicated to the beneficiary in advance.

PDAC Verification and Documentation Requirements

PDAC (Pricing, Data Analysis and Coding) product verification is a critical step for DME suppliers billing L4397 to Medicare. The PDAC is a CMS contractor that reviews orthotic products and assigns the appropriate HCPCS code for each model. When a supplier bills L4397, Medicare expects the product dispensed to be one that the PDAC has verified as appropriately coded under L4397. Billing a product that has been assigned a different HCPCS code by the PDAC is a billing error regardless of how similar the product may appear to an L4397 device.

Suppliers can verify PDAC coding assignments through the CGS Medicare coding verification resource, which provides current coding decisions for DMEPOS products. Maintaining a current list of PDAC-verified products stocked by the supplier, and cross-referencing it at dispensing, is a standard compliance practice.

Documentation Requirements per CMS Policy Article A52457

Per Social Security Act §1834(h)(5), documentation created by an orthotist or prosthetist is considered part of the patient’s medical record for purposes of determining medical necessity. This statutory provision means that orthotist fitting notes, evaluation reports, and follow-up documentation carry the same weight as physician records during a DME MAC audit. The complete documentation file for an L4397 claim should include the following elements.

• Written order from the treating physician specifying the type of AFO, the diagnosis, and the clinical need
• Face-to-face clinical evaluation by the treating practitioner documenting the criteria met under LCD L33686, including goniometric pre-treatment passive range of motion measurement when criteria 1-4 apply
• Orthotist or supplier dispensing notes confirming the product dispensed, the HCPCS code selected, and the fitting method used (custom fitted vs. off-the-shelf)
• PDAC verification documentation for the specific product model dispensed
• Signed delivery confirmation from the beneficiary acknowledging receipt
• ABN (if applicable) signed by the beneficiary before service when criteria may not be met

Using digital documentation workflows that capture all these elements at the point of care reduces the risk of incomplete records at the time of a retrospective audit. Paper-based systems make it difficult to verify completeness without manually reviewing each patient file.

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Bundling Considerations: L4397 and L1902 for Plantar Fasciitis

When a patient presents with plantar fasciitis and a supplier provides both a night splint (L4397) and an air heel cushion (HCPCS code L1902), a bundling issue arises for Medicare billing. According to guidance from the New York State Podiatric Medical Association, when both items are billed for the same foot in the same claim period, Medicare will deny L1902 as inclusive to the more expensive DME item. Only L4397 should be billed to Medicare in this scenario.

This bundling rule does not necessarily prohibit billing both items to non-Medicare payers with different coverage policies. Commercial insurers may reimburse both products separately. The key practice management implication is that billing staff must apply different claim logic depending on payer type, making payer-specific billing rules a necessary part of revenue cycle management for orthotic suppliers. A compliance management system that applies payer-specific edits at the claim level can flag this bundling scenario automatically before submission.

Fee Schedule and Reimbursement Rates for HCPCS Code L4397

Medicare reimbursement rates for HCPCS Code L4397 are set under the Medicare DMEPOS fee schedule, which is updated annually by CMS and varies by geographic locality. The fee schedule amount represents the maximum Medicare reimbursement; actual payment equals 80% of the fee schedule after the Part B deductible is met, with the remaining 20% payable by the beneficiary or a supplemental insurer.

Rates differ between rural and non-rural areas and are adjusted by a competitive bidding framework in applicable competitive bidding areas (CBAs). Suppliers operating within CBAs must be accredited contract suppliers to bill Medicare for items covered under competitive bidding. L4397 has historically been included in competitive bidding program rounds, though CMS adjusts the product categories included in each round. For current locality-specific rates, suppliers should query the CMS DMEPOS fee schedule lookup tool directly, as published rates can differ from what billing software systems carry if those systems are not updated promptly at the start of each calendar year.

Noridian Healthcare Solutions, which administers DME MAC Jurisdictions A and D, made significant policy article revisions in December 2023. Among the changes, Noridian removed prior language specifying that certain HCPCS code narratives applied regardless of whether the product was provided as custom-fit or OTS. The net effect is that the custom-fit vs. OTS distinction now carries more weight in code selection than it did before March 2021. Suppliers should review their internal policies to confirm L4397 is being applied only to products that are genuinely dispensed as off-the-shelf items. Billing workflows supported by HIPAA-compliant clinic software that captures the dispensing method at the product level can help enforce this distinction consistently.

Billing Tips and Common Denial Patterns for L4397

Most L4397 denials fall into a small number of predictable categories. Understanding the denial pattern before it occurs is more cost-effective than managing appeal workflows after the fact.

• Missing or incorrect modifier: KX appended without supporting documentation, or GA submitted without a valid signed ABN. Review documentation completeness before appending KX.
• Unsupported diagnosis code: ICD-10 code not listed in Policy Article A52457’s approved diagnosis list for L4397. Cross-reference the current policy article at the time of billing, not an older version.
• Wrong code for ambulatory device: An AFO intended for walking dispensed and billed as L4397. The product’s intended use and the patient’s ambulatory status must both support the positioning-use classification.
• PDAC code mismatch: Product dispensed has a PDAC coding assignment different from L4397. Verify PDAC status for every product model in stock before billing.
• Wrong fitting code: A device that required substantial customization at fitting billed as L4397 (off-the-shelf) instead of L4396 (custom fitted). Match the code to the actual level of expertise required at fitting.
• Laterality error: Bilateral devices billed on a single line without RT/LT modifiers, or modifiers applied to the wrong foot.
• Missing face-to-face documentation: Claim submitted before the treating practitioner’s evaluation note, including goniometric range of motion measurement when applicable, has been received by the supplier and placed in the file.

Tracking denial reasons by code and modifier at the practice level, and reviewing that data monthly, is one of the most reliable ways to identify systemic billing problems before they compound. Coding documentation practices that align diagnosis selection with policy article requirements at the time of order entry reduce reliance on retrospective correction and rework cycles.

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Conclusion

HCPCS Code L4397 is a narrow but heavily audited billing code. The most common mistakes, missing KX documentation, incorrect diagnosis codes, miscoded fitting method, and PDAC mismatches, all stem from gaps between clinical decision-making and billing workflow. Closing those gaps requires documented processes, not just coding knowledge.

Pabau’s claims management software helps orthotic suppliers and billing teams build those processes into their daily workflows, from order entry through claim submission and denial management. To see how Pabau handles HCPCS L-code billing workflows in practice, book a demo with the team.

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