L5631 HCPCS Reimbursement & Policy Benchmarks | OpenPayer

Summary & Overview

HCPCS L5631: Addition to Lower Extremity, Above-Knee Acrylic Socket

HCPCS Level II code L5631 represents an addition to a lower extremity prosthesis for above-knee or knee-disarticulation patients that incorporates an acrylic socket. This durable medical equipment/prosthetic supply code matters nationally because it affects coverage decisions, reimbursement for prosthetic providers, and access to socket modifications that can impact mobility and prosthesis fit. The code is relevant to clinicians, prosthetists, billing staff, and payers managing prosthetic benefits.

Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the clinical service and typical sites of care, payer considerations and coverage patterns where available, common billing modifiers and administrative notes, and related coding context. The publication provides benchmarks for utilization and reimbursement where available and highlights policy and documentation elements that influence medical necessity determinations.

The content provides practical, policy-relevant context about prosthetic socket additions for above-knee and knee-disarticulation amputees, clarifies what this HCPCS Level II code denotes, and outlines administrative and clinical considerations that affect claims processing and beneficiary access.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicareL5631HCPCS Level IIprostheticslower extremityabove-kneeknee disarticulationacrylic socketdurable medical equipmentprosthetic modification

Billing Code Overview

HCPCS Level II code L5631 describes an addition to a lower extremity prosthesis for above knee or knee disarticulation with an acrylic socket. The service is a prosthetic component used to modify or augment an existing above-knee or knee-disarticulation prosthetic socket by adding an acrylic socket element.

Service type: Prosthetic addition/modification for lower extremity amputation
Typical site of service: Outpatient prosthetics clinic, orthotics and prosthetics (O&P) provider office, or specialized rehabilitation facility

Clinical & Coding Specifications

Clinical Context

A 62-year-old patient with a transfemoral (above-knee) amputation presents for prosthetic socket modification to accommodate residual limb volume changes and improve socket fit and comfort. The patient is seen in an outpatient prosthetics clinic staffed by a certified prosthetist-orthotist and a prosthetic technician. During the visit the clinician evaluates the residual limb, reviews prior socket fit, documents areas of pressure or soft-tissue change, and determines that an acrylic socket addition is required to augment an existing above-knee socket (knee disarticulation/above-knee level). The workflow includes: prosthetist evaluation and measurement, mold or digital capture of the socket interface, fabrication of an acrylic addition to the existing socket in a lab or onsite, fitting and modification, and final functional check with gait assessment. Typical site of service is an outpatient prosthetics clinic or prosthetic laboratory associated with an orthopedic or rehabilitation facility. The procedure is billed as an addition to a lower extremity, above knee or knee disarticulation acrylic socket using billing code L5631 with applicable modifiers for laterality, service component, or unusual circumstances.

Coding Specifications

Modifier	Description	When to Use
`LT`	Left side	Use when the addition applies to the left lower extremity socket.

HCPCS L7009: Electric/Myoelectric Adult Prosthetic Hook

HCPCS-L8430-PROSTHETIC-SOCK-MULTIPLE-PLY-ABOVE-KNEE

HCPCS Level II L8430: Prosthetic Sock, Multiple Ply, Above Knee

HCPCS-L8480-PROSTHETIC-SOCK-ABOVE-KNEE-FITTING

HCPCS Level II L8480: Prosthetic Sock, Single Ply, Above-Knee Fitting

HCPCS-L6696-UPPER-EXTREMITY-PROSTHESIS-CUSTOM-SOCKET-INSERT-INITIAL

HCPCS Level II L6696: Custom Upper-Extremity Prosthetic Socket Insert, Initial

HCPCS-L6350-INTERSCAPULAR-THORACIC-SHOULDER-BULKHEAD-PROSTHESIS

HCPCS L6350: Interscapular Thoracic Upper-Extremity Prosthetic Socket

HCPCS-L5816-ENDOSKELETAL-POLYCENTRIC-KNEE-SHIN-MECHANICAL-LOCK

HCPCS L5816: Endoskeletal Knee-Shin Addition, Polycentric Knee with Mechanical Lock

HCPCS-L8694-AUDITORY-OSSEOINTEGRATED-TRANSDUCER-REPLACEMENT

HCPCS L8694: Auditory Osseointegrated Transducer/Actuator Replacement

HCPCS-L6708-PROSTHETIC-TERMINAL-DEVICE-HAND-MECHANICAL-VOLUNTARY-OPENING

HCPCS Level II L6708: Mechanical Voluntary-Opening Hand Terminal Device

HCPCS-L5683-LOWER-EXTREMITY-CUSTOM-SOCKET-INSERT-SILICONE-GEL

HCPCS L5683: Lower Extremity Custom Socket Insert, Silicone Gel

HCPCS-L6640-UPPER-EXTREMITY-SHOULDER-ABDUCTION-JOINT-PAIR

HCPCS Level II L6640: Upper Extremity Shoulder Abduction Joint, Pair

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Taxonomy Code	Specialty	Notes
`332B00000X`	Prosthetics/Orthotics	Certified prosthetist-orthotist who evaluates and fits prosthetic sockets.
`208U00000X`	Physical Medicine & Rehabilitation	Physiatrist involved in prosthetic management and functional assessment.
`207K00000X`	Orthopedic Surgery	Orthopedic surgeons who may perform amputation surgery and coordinate prosthetic care.
`103T00000X`	Physical Therapy	Physical therapists who perform gait training and functional fitting checks.
`363A00000X`	Occupational Therapy	Occupational therapists who assist with ADL training and prosthetic integration.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`Z43.1`	Fitting and adjustment of prosthetic limb	Common encounter diagnosis when performing prosthetic socket additions and adjustments.
`Z89.610`	Acquired absence of left leg above knee	Relevant when the socket addition is for a left transfemoral amputation.
`Z89.611`	Acquired absence of right leg above knee	Relevant when the socket addition is for a right transfemoral amputation.
`Z89.619`	Acquired absence of unspecified leg above knee	Use when laterality is unspecified in documentation.
`T87.89`	Other complications of amputation stump	Used when socket modification is needed due to stump complications such as pressure areas or skin breakdown.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`97760`	Orthotic and prosthetic management and training; initial orthotic/prosthetic evaluation	Performed prior to fabrication to evaluate needs, establish baseline function, and determine socket requirements.
`97763`	Prosthetic training, upper and/or lower extremity, initial encounter	Used for gait training and patient instruction after socket fitting and delivery.
`97750`	Physical performance test or measurement	Utilized for outcome measurement of function and fits following socket addition.
`99070`	Supplies and materials (used with modifier)	May be reported for non-routine supplies used in fabrication when payer allows separate supply billing.
`99080`	(Administrative)	Data not applicable; use administrative codes per payer policy as needed.

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