HCPCS Code L1845: Knee orthosis double upright billing guide

Key Takeaways

HCPCS Code L1845 describes a prefabricated knee orthosis with double uprights, condylar pads, and an adjustable flexion and extension joint providing medial-lateral and rotation control.

Medicare covers L1845 through one of two paths under LCD L33318: a recent knee injury or surgery, or an ambulatory beneficiary with documented knee instability – the KX modifier attests the criteria are met and on file.

Documentation updated August 12, 2024 must include beneficiary authorization, proof of delivery, continued need records, and treating practitioner notes.

Pabau’s claims management software and digital forms help DME suppliers and orthotists maintain compliant documentation and streamline L1845 billing workflows.

The full official description of HCPCS Code L1845 is: Knee orthosis (KO), double upright, thigh and calf, with adjustable flexion and extension joint (unicentric or polycentric), medial-lateral and rotation control, with or without varus/valgus adjustment, prefabricated item that has been trimmed, bent, molded, assembled, or otherwise customized to fit a specific patient by an individual with expertise.

The short description used in billing systems is “KO DOUBLE UPRIGHT PRE CST.”

This code has been effective for Medicare claims with dates of service on or after July 1, 2008, per CMS Policy Article A52465. It sits within the HCPCS Level II L-code range, which covers orthotic procedures for the lower limb.

Key device components for L1845

For a device to correctly bill under HCPCS Code L1845, it must include all of the following structural components as verified by PDAC and Palmetto GBA DMECS:

• Double uprights on both the medial and lateral sides of the knee
• Thigh and calf cuffs extending above and below the joint
• Condylar pads for additional medial-lateral stabilization
• Adjustable flexion and extension joint that is either unicentric or polycentric in design
• Medial-lateral and rotation control as a functional feature of the orthosis
• Varus/valgus adjustment capability (optional but may be present)
• Prefabricated construction customized to fit the specific patient by an individual with expertise

The customization requirement is what separates L1845 from off-the-shelf prefabricated codes. The device must be trimmed, bent, molded, assembled, or otherwise modified by a qualified individual before being dispensed. This is not an over-the-counter brace handed to a patient in a box.

Medicare coverage criteria for HCPCS Code L1845

Coverage under LCD L33318 (Knee Orthoses) groups L1845 with L1843, L1851, and L1852 as adjustable-joint knee orthoses. These codes share the same coverage criteria set. Maintaining thorough patient compliance documentation from the treating practitioner is essential to supporting these criteria at audit.

Medicare covers HCPCS Code L1845 when the medical record supports one of the following two coverage paths. Documentation of pain alone, or a subjective report of the knee giving way, does not meet either path.

Path 1: Recent injury or knee surgery

The beneficiary has had a recent injury to, or a surgical procedure on, the knee. Operative reports, discharge summaries, or orthopedic notes documenting the injury or procedure and the need for orthotic support satisfy this path. The claim must carry a supporting ICD-10-CM diagnosis from Group 2 or Group 4 of the LCD-related Policy Article (A52465).

Path 2: Ambulatory with knee instability

The beneficiary is ambulatory and has knee instability. The record must include the treating practitioner’s examination and an objective description of joint laxity, such as varus/valgus instability or an anterior/posterior Drawer test result. The claim must carry a supporting ICD-10-CM diagnosis from Group 4 of the Policy Article (A52465).

For physical therapy practices involved in post-surgical rehabilitation, coordinating with the prescribing physician to ensure LCD-aligned documentation is captured before the orthosis is ordered prevents most downstream denials.

Documentation requirements for HCPCS Code L1845

Documentation requirements for L1845 were updated effective August 12, 2024, per the Noridian Medicare Documentation Checklist (last updated September 20, 2024). Every DME supplier billing this code needs current documentation practices in place. Using medical forms at your healthcare practice that capture all required data points from the start reduces rework at the time of audit or appeal.

The required documentation set for HCPCS Code L1845 claims includes:

• Beneficiary authorization – signed by the patient or their authorized representative
• Proof of delivery (POD) – must show the item was delivered to the beneficiary, with date and beneficiary signature
• Continued need documentation – records demonstrating the ongoing medical necessity at each re-evaluation
• Continued use documentation – confirmation the beneficiary is actively using the device
• Medical records from the treating practitioner – including examination findings, diagnosis, and the clinical rationale for prescribing the orthosis

Maintaining compliant clinical records management for each L1845 patient means every document above is timestamped, retrievable, and associated with the correct claim. Pabau’s client record system supports this level of documentation organization across a multi-provider DME practice.

Beyond the core set, the treating practitioner’s notes must include objective clinical findings that map to one of the two LCD L33318 coverage paths. A note that says only “patient has knee pain” is not sufficient. HIPAA compliance for medical offices also requires that any documentation shared between the DME supplier and the treating clinician follows appropriate authorization and disclosure protocols.

HCPCS Code L1845 chart: Related knee orthosis codes

L1845 is one of several knee orthosis codes covered under LCD L33318. Choosing the wrong code in this family is a common billing error that triggers audits. The table below compares the codes most frequently confused with L1845.

The critical distinction among the double-upright codes is the level of fitting. L1845 is a prefabricated device custom-fitted to the patient by a qualified individual who trims, bends, or molds it. L1852 is the off-the-shelf version, requiring minimal or no fitting. L1846 is the custom-fabricated version, built from a patient-specific model or template.

Billing L1845 when only an off-the-shelf device (L1852) was dispensed, or billing the custom-fabricated L1846 without fabrication records on file, is a compliance risk that can trigger recoupment. Keeping client records up to date with device delivery records and fabrication documentation is the first line of defense against this type of error.

PDAC verification and HCPCS Code L1845 compliance

The PDAC (Pricing, Data Analysis and Coding) contractor, administered by Palmetto GBA, verifies whether specific DME products meet the requirements of HCPCS codes including L1845. Suppliers should confirm that any prefabricated knee orthosis they plan to bill under this code has received PDAC verification before dispensing to Medicare beneficiaries.

PDAC publishes a DMECS (Durable Medical Equipment Coding System) database at the Palmetto GBA website where suppliers can look up whether a specific product model has been verified for L1845.

The original PDAC advisory article on L1845 (SADMERC archived) confirms the device must have double uprights, condylar pads, and an adjustable flexion and extension joint, with the joint being either unicentric or polycentric. Good compliance management practices include maintaining a product verification log tied to each HCPCS code used in your billing workflow.

Products not verified by PDAC for L1845 that are billed under this code will be denied or subject to recoupment on audit. The CGS Medicare Coding Verification process outlines how MACs handle PDAC coding questions for DMEPOS suppliers. Suppliers operating across multiple MAC jurisdictions should note that L1845, L1843, L1851, and L1852 are all included in CMS Required programs as confirmed by CGS Medicare.

Modifiers used with HCPCS Code L1845

Modifier selection for L1845 directly determines whether Medicare pays, holds, or denies the claim. Using the wrong modifier, or omitting a required modifier, is one of the most correctable billing errors in DME orthotic coding.

Reviewing a HIPAA compliance checklist alongside your modifier usage protocols helps ensure consistent, audit-ready claims.

The KX modifier is the most important modifier for routine L1845 billing. Without it, the MAC will deny the claim or apply a medical review flag. It is the supplier’s attestation that documentation supporting LCD L33318 coverage criteria is on file.

Never add KX if the documentation does not actually support coverage, as this constitutes a false claim. When documentation is borderline, use GA after obtaining a signed Advance Beneficiary Notice (ABN) from the patient before dispensing the orthosis.

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ICD-10 diagnosis codes that support L1845 medical necessity

Every L1845 claim needs at least one ICD-10-CM diagnosis code that establishes medical necessity. The diagnosis must be consistent with one of the two LCD L33318 coverage paths. Mismatching the diagnosis to the coverage path leads to denial, even when the device itself is appropriate.

Pabau’s digital intake forms can be configured to capture the treating clinician’s diagnosis at the point of referral, reducing transcription errors on claims.

Commonly used ICD-10 codes with HCPCS Code L1845 include:

• M23.619 – Other spontaneous disruption of anterior cruciate ligament of unspecified knee (instability)
• M25.361 – Other instability, right knee
• M25.362 – Other instability, left knee
• M17.11 – Primary osteoarthritis, right knee
• M17.12 – Primary osteoarthritis, left knee
• Z96.641 – Presence of right artificial knee joint (post-surgical criterion)
• Z96.642 – Presence of left artificial knee joint (post-surgical criterion)
• S82.001A – Fracture of patella, initial encounter for closed fracture (post-fracture criterion)

This list is not exhaustive. The diagnosis code must be selected based on the individual patient’s documented clinical condition, not from a generic list. For laterality, always use the specific left (2) or right (1) code when available rather than the unspecified (9) version. Specificity reduces audit risk and improves claim adjudication speed.

Billing guidelines and reimbursement for HCPCS Code L1845

Reimbursement for L1845 is based on the Medicare DMEPOS Fee Schedule, which varies by MAC jurisdiction and is updated annually. Current fee schedule amounts can be looked up using the CMS Physician Fee Schedule lookup tool, or for DMEPOS-specific rates via the CMS DMEPOS fee schedule files.

Rates also vary depending on whether the supplier is in a Competitive Bidding Area (CBA). Maintaining paperless practice workflows that pull fee schedule data directly into the billing system reduces manual rate errors.

Key billing rules for HCPCS Code L1845 claims:

• Modifier NU, RR, or UE is required to indicate whether the item is being purchased new, rented, or sold as used equipment
• Modifier KX must accompany every covered claim to attest that LCD coverage criteria are met and on file
• Prior authorization is required nationally – L1845 is on CMS’s Required Prior Authorization List, so a provisional affirmation from the DME MAC is a condition of payment before delivery
• Face-to-face encounter and Written Order Prior to Delivery (WOPD) are required – L1845 is on CMS’s Required Face-to-Face and WOPD List; the supplier must obtain both records before dispensing the orthosis
• DMEPOS Competitive Bidding Program affects rates in designated CBAs – suppliers must be contracted to receive Medicare payment in those areas
• One orthosis per claim episode is standard; replacement claims require documentation of medical necessity for replacement and must follow Medicare’s replacement frequency guidelines
• Continued need re-evaluations are required for long-term use; document that the patient still meets coverage criteria and is actively using the device

Practices managing high volumes of L1845 claims benefit from integrating this code family into a systematic audit workflow that checks modifier accuracy, diagnosis-to-criterion alignment, and POD completeness before submission.

The value of building a compliant billing workflow around L1845 cannot be overstated. Practices that invest in front-end documentation review, from the treating clinician’s order through POD capture, consistently achieve higher clean claim rates and lower denial write-offs.

Exploring features that save private practices time on administrative tasks frees clinical staff to focus on the documentation quality that drives successful reimbursement.

Conclusion

HCPCS Code L1845 is a well-defined but frequently misapplied code. Denials almost always trace back to one of three gaps: a device that does not meet all structural requirements, documentation that does not align with LCD L33318 coverage criteria, or incorrect modifier usage. Practices that close these gaps with systematic pre-billing review and well-maintained client records consistently bill L1845 cleanly.

Pabau’s practice management platform gives DME suppliers and multi-discipline practices the tools to keep every L1845 claim audit-ready, from configuring digital forms that capture LCD-aligned documentation to tracking claim status through adjudication. Book a demo to see how Pabau supports compliant orthotic billing documentation at scale.

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