CPT® Code 97024

Quick Reference

• Code definition: CPT 97024 reports the application of diathermy (shortwave or microwave electromagnetic heating) to one or more body areas as a supervised physical medicine modality.
• Key billing rule: Untimed and unsupervised (no constant attendance required); bill exactly one unit per date of service regardless of duration, number of body areas treated, or frequency of application within the session. MUE = 1 [4].
• Modifier essentials: Append GP for outpatient physical therapy plans of care, GO for occupational therapy, GN for speech-language pathology. Above the annual financial limitation threshold, KX is mandatory to attest continued medical necessity; omitting KX causes automatic denial [1][2].
• Documentation must-have: A certified physician or NPP plan of care (POC) must exist before billing. Each session note must identify the modality, body area treated, and patient response tied to a POC goal.
• Top confusion point: Do not use 97024 for therapeutic ultrasound. Ultrasound is coded 97035 (constant attendance, timed). The parenthetical "eg, microwave" in the descriptor identifies the electromagnetic heating category, not acoustic energy.
• Payer alert: Medicare Part B reimburses approximately $7.35 nationally in 2026 (total RVU 0.22, conversion factor 33.4009) [1]. Under OPPS, 97024 carries a $0.00 payment; hospital outpatient settings receive no separate reimbursement for this code [1].

When to Use This Code

97024 captures diathermy applied as a standalone therapeutic intervention. Appropriate clinical scenarios include:

• Subacute or chronic musculoskeletal conditions where deep tissue heating supports increased circulation and tissue extensibility: osteoarthritis, rheumatoid arthritis, joint contractures, bursitis, tendinitis, muscle strains and sprains
• Pre-exercise warm-up using diathermy to improve soft tissue pliability before therapeutic exercise or manual therapy
• Sinusitis where heat application to facial structures is part of a supervised therapy plan
• Shortwave diathermy (27.12 MHz radiofrequency) is the modality most commonly applied in current clinical practice; microwave diathermy (~915 or 2,456 MHz) heats more superficially and is largely obsolete

Setting context: 97024 is appropriate for outpatient PT and OT clinics (non-facility setting) under a certified POC. It is valid for professional billing in the SNF setting but is not separately payable to Medicare Part B when the patient is in a Medicare-covered SNF stay (included in the SNF PPS rate). For home health episodes, 97024 bundles into home health PT codes per NCCI [3].

What falls outside this code: Therapeutic ultrasound (97035), infrared lamp (97026), and paraffin bath (97018) are each separately coded despite being superficially similar heat-based modalities. If the therapist applies a constant-attendance electrical stimulation technique, that is 97032, not 97024.

Code Differentiation Table

The most consequential distinction is 97024 versus 97035. Despite both being "diathermy" in the broad clinical sense, CPT assigns them to entirely different billing categories: 97024 is supervised and untimed; 97035 is constant-attendance and timed. Using 97024 to report therapeutic ultrasound is incorrect regardless of the equipment used.

flowchart TD
    A[Heat/Energy Modality Applied] --> B{Energy type?}
    B -->|Acoustic: ultrasound transducer| C[97035 - Ultrasound, timed]
    B -->|Electromagnetic: shortwave or microwave| D{Attendance?}
    D -->|Supervised, no constant attendance| E[97024 - Diathermy]
    D -->|Constant attendance, 1:1 contact| F[Consider 97032 or 97039]
    B -->|Infrared lamp| G[97026 - Infrared]
    B -->|Superficial heat/cold packs| H[97010 - Hot or cold packs]
    B -->|Paraffin wax| I[97018 - Paraffin bath]

Billing and Modifier Rules

Units: One unit per date of service, hard stop. Treating bilateral knees, lumbar paraspinals, and a shoulder in the same session still equals one unit. MUE = 1 with MAI 3 (clinical data basis), meaning CMS considers >1 unit per day clinically impossible [4].

Therapy discipline modifiers (Medicare Part B outpatient):

KX modifier threshold: CMS requires KX on all therapy claims once the beneficiary's combined PT+SLP charges for the year exceed the annual financial limitation threshold ($2,330 for PT+SLP combined in 2025; verify current 2026 amount at the CMS therapy services page) [2]. KX attests that documentation supports continued medical necessity per a current, compliant POC.

NCCI bundling for 97024 [3]:

97024 bundles as Column 2 into: Radiation hyperthermia codes 77600 to 77620 and home health PT codes G0151, G0157, G0159 [3].

PCTC Indicator 7: Modifiers 26 (professional component) and TC (technical component) do not apply. This is classified as a physical therapy service, not a split-billing procedure.

CPT guideline note: CPT instructs that codes 97010 to 97763 report each distinct procedure performed; modifier 51 should not be appended to codes in this range.

Documentation Essentials

Required elements per session:

• Modality identified as diathermy (shortwave or microwave, as applicable)
• Body area(s) treated and laterality
• Duration of application (documents clinical decision even though units are not time-based)
• Patient's response and tolerance
• Connection to a current POC goal (e.g., "diathermy applied to right knee to reduce joint stiffness prior to therapeutic exercise targeting ambulation distance goal")

Plan of care requirements [5]: A certified POC must be in place before the first treatment. The POC must include: diagnosis, treatment goals (long-term functional), type of treatment, frequency, duration, therapist signature, and physician/NPP certification. CMS may recover all claims from a date of service if no valid POC existed.

Progress notes: At minimum every 10 treatment visits or 30 days, whichever comes first, documenting measurable functional progress toward POC goals.

Audit red flags:

• Treatment notes that say only "diathermy applied" with no body area, goal connection, or patient response
• Identical notes across sessions ("cloned documentation") with no indication of patient progress or clinical decision-making
• POC that lists only impairment-based goals (pain 3/10) without functional correlates (return to work, ambulation distance)
• Diathermy billed every session as a standard protocol add-on without individualized justification
• No documentation of contraindication screening (pacemaker, metal implants, pregnancy) in the initial evaluation when those risks are plausible

Medicare, Commercial and Medicaid Payer Rules

Medicare

97024 is an active code under the Medicare Physician Fee Schedule [1]:

• 2026 total RVU: 0.22; national payment approximately $7.35 (conversion factor 33.4009)
• OPPS: Payment = $0.00. The code is paid under the fee schedule or other payment system, not under OPPS (APC Status Indicator: Service Paid under Fee Schedule or Payment System other than OPPS). Hospital outpatient facilities should not expect a separate reimbursement line for 97024 under a UB-04 claim
• SNF Consolidated Billing: 97024 is included in the SNF PPS consolidated billing rate; not separately billable to Medicare Part B for a beneficiary in a covered SNF stay
• No NCD exists specific to diathermy or 97024; coverage is governed by the Part B therapy benefit (42 CFR §410.60) and any applicable MAC LCD. No MAC-specific LCD for 97024 alone was identified; therapy modalities are typically addressed under broader physical therapy LCDs. Verify active LCDs at the CMS Medicare Coverage Database [7]
• BETOS category: P6C (Minor procedures, other, Medicare fee schedule)

Commercial Payers

Commercial coverage for 97024 broadly follows CPT conventions but payer-specific rules vary:

• Some commercial plans follow the Medicare bundling pattern for supervised modalities; others allow separate billing of 97010 and 97024 on the same day without a modifier. Verify each plan's modality bundling policy before unbundling
• Prior authorization is not commonly required for individual modality codes, but therapy visit limits and diagnosis-driven restrictions vary by plan
• Therapy discipline modifiers GP/GO are generally not required for commercial claims but some payers request them for internal routing; confirm by payer

Medicaid

No state-specific coverage details for 97024 were identified in the research. Managed Medicaid plans frequently impose visit frequency caps and may require prior authorization for extended therapy episodes. Verify individual state fee schedules and managed Medicaid plan policies before billing.

Common Denials and Prevention

Denial: Units exceed MUE Medicare or clearinghouse auto-denies when more than one unit of 97024 is submitted per date of service. Root cause is typically a billing entry error or a misunderstanding that treating multiple body areas increases units. Prevention: configure billing software to enforce a hard cap of one unit per day for 97024. MUE = 1, no exception [4].

Denial: Missing therapy discipline modifier CMS requires GP or GO on all Part B outpatient therapy claims; omission results in denial without remittance explanation. Prevention: set a claim scrubbing rule that flags 97024 on Part B outpatient claims without GP or GO appended.

Denial: KX modifier absent above threshold Once cumulative PT+SLP charges exceed the annual financial limitation threshold, 97024 claims without KX are automatically denied. Prevention: implement a threshold tracker in the billing system; apply KX to all therapy codes including 97024 when the threshold is crossed. Documentation must be in compliance before KX is appended [2].

Denial: Lack of medical necessity or missing plan of care Post-payment audit recoveries and pre-payment reviews cite absence of a certified POC or treatment notes that do not connect diathermy to a functional goal. Prevention: audit a sample of therapy records monthly to confirm POC certification dates precede dates of service, and that daily notes explicitly link each modality to a POC objective.

Denial: NCCI bundling with 97026 or 97018 When 97024 and 97026 or 97018 are billed same day without a modifier, the bundled code is denied. Prevention: when both modalities are genuinely medically necessary and applied to distinct body areas or at separate times for distinct therapeutic purposes, append modifier 59 (or XS for distinct anatomical site) and ensure the session note documents the separate clinical rationale for each [3].

Coding Scenarios

Scenario 1: Knee osteoarthritis in outpatient PT clinic

A patient with right knee osteoarthritis presents for a routine PT session. The therapist applies shortwave diathermy to the right knee for 20 minutes to reduce joint stiffness, then transitions to therapeutic exercises.

Correct coding: 97024-GP + therapeutic exercise codes with GP; one diagnosis code supporting knee OA (e.g., ICD-10-CM M17.11)

Why: 97024 is untimed; 20 minutes still equals one unit. GP is mandatory on the outpatient PT claim. Therapeutic exercises are coded separately under the timed rules applicable to those codes.

Scenario 2: Same-day diathermy and hot packs, Medicare patient

A PT applies moist hot packs to the lumbar region for 10 minutes followed by shortwave diathermy to the lumbar paraspinals in the same session.

Correct coding: 97024-GP only

Why: 97010 (hot/cold packs) is both NCCI-bundled with 97024 and carries Medicare Bundled status with $0.00 separate payment. Appending modifier 59 to 97010 does not generate additional revenue under Medicare. For commercial payers, verify the plan's modality bundling policy before billing 97010 separately [3].

Scenario 3: Diathermy billed under OPPS at a hospital outpatient department

A hospital-employed PT applies shortwave diathermy during an outpatient PT session. The billing team includes 97024-GP as a line item on the UB-04.

Correct coding: 97024 may appear on the claim but will generate $0.00 reimbursement under OPPS

Why: 97024 is not separately payable under OPPS (APC Status Indicator: paid under fee schedule or other payment system, not OPPS). Hospital billing staff should not expect a separate payment line; the service is packaged. This is not a billing error but a payment system characteristic that revenue cycle teams must understand to set accurate expectations [1].

Scenario 4: Diathermy on the same day as a PT re-evaluation

A physical therapist performs a formal re-evaluation (97164) to update the POC and then provides diathermy (97024) in the same visit.

Correct coding: 97164-GP + 97024-59-GP (or 97024-XS-GP if a distinct anatomical site is documented)

Why: NCCI bundles 97024 as Column 2 to 97164 Column 1. Modifier 59/XS is allowed per the edit table. The session note must document the re-evaluation as a distinct, separately identifiable service from the modality treatment, with separate clinical rationale for each [3].

Related Codes

• 97010: Hot or cold packs; supervised superficial thermal modality; NCCI-bundled with 97024 and Medicare-bundled (no separate payment)
• 97018: Paraffin bath; supervised superficial heat; NCCI bundles with 97024 same day; modifier 59/XS required for separate billing
• 97026: Infrared; supervised radiant heat; NCCI Column 1 to 97024 Column 2; modifier required when both are medically necessary same day
• 97032: Electrical stimulation (attended); constant attendance, timed modality; often confused with supervised modalities when deciding attendance requirements
• 97035: Ultrasound; constant attendance, timed; the code to use for therapeutic ultrasound, never 97024
• 97164: Re-evaluation of PT plan of care; NCCI bundles with 97024 same day; modifier 59/XS required
• 97168: Re-evaluation of OT plan of care; same NCCI bundling pattern as 97164

Sources

1. CMS 2026 Physician Fee Schedule RVU Files (RVU26A) — CMS, released 12/29/2025. 2026 RVUs, status indicators, conversion factor, OPPS payment indicators for 97024.
2. CMS Outpatient Therapy Services — KX Modifier / Financial Limitation Threshold — CMS. Annual therapy financial limitation thresholds; verify 2026 amounts at source.
3. CMS NCCI PTP Edits — Physician/Practitioner Table v32.1r0 — CMS, 2026. All Column 1/Column 2 NCCI edit pairs for 97024 verified.
4. CMS Medically Unlikely Edits (MUE) — Practitioner Services Q2 2026 — CMS, effective 04/01/2026. MUE = 1, MAI 3 for CPT 97024.
5. CMS Medicare Benefit Policy Manual (IOM Pub. 100-02, Chapter 15) — CMS. Therapy documentation requirements, plan of care, and medical necessity criteria.
6. CMS Medicare Claims Processing Manual (IOM Pub. 100-04, Chapter 5 and Chapter 15) — CMS. Billing rules for therapy services and modifier requirements.
7. CMS Medicare Coverage Database — CMS. Source for verifying MAC LCDs; search "physical therapy modalities" for applicable local coverage articles.