CPT code 01390: Anesthesia for Tibia, Fibula & Patella Procedures

Key Takeaways

CPT code 01390 covers anesthesia for all closed procedures on the upper ends of the tibia, fibula, and/or patella

The code carries 3 base units, consistently verified across CMS, VA, DOL, and multiple state Medicaid fee schedules

Billing uses the anesthesia formula: (Base Units + Time Units + Modifying Units) x Conversion Factor; modifier selection depends on provider type and supervision ratio

Pabau’s claims management software helps anesthesia practices track modifiers, time units, and payer-specific rules in one place

Closed procedures on the upper knee region are among the most frequently miscoded anesthesia encounters in orthopedic billing. In fact, the difference between a closed and an open approach changes the CPT code, the base unit value, and the reimbursement outcome. Getting it wrong means denied claims, delayed payment, or compliance exposure.

CPT code 01390 is the correct code for anesthesia provided during closed procedures on the upper ends of the tibia, fibula, and/or patella. This reference covers the official descriptor, base units, time-unit billing formula, qualifying modifiers, common ICD-10 pairings, payer policies, and how 01390 compares to adjacent codes in the knee and popliteal area range. Practices working through physical therapy practices or orthopedic settings will find this guide directly applicable to their workflows.

CPT code 01390: Anesthesia for closed procedures on tibia, fibula, and patella

The American Medical Association (AMA) maintains CPT code 01390 within the anesthesia section. Its official full descriptor is:

Anesthesia for all closed procedures on upper ends of tibia, fibula, and/or patella

Specifically, this code belongs to the broader subsection “Anesthesia for Procedures on the Knee and Popliteal Area.” The “closed” designation is the critical clinical qualifier. It means the surgical approach does not open the joint or bone with an incision exposing the cortex. Typical encounters billed under 01390 include:

• Closed reduction of proximal tibia fractures
• Closed reduction of fibula fractures at or near the knee
• Closed reduction of patella fractures
• Application of external fixator without open incision
• Manipulation under anesthesia involving the proximal tibia or patella

When the surgeon opens the bone or joint with an incision, the correct code shifts to CPT 01392. Therefore, coders should confirm the operative note’s approach language before assigning 01390, as “closed” must be documented explicitly.

Base units and anesthesia billing formula for CPT code 01390

CPT 01390 carries 3 base units. Notably, this value is consistently verified across multiple government payer sources: the VA Community Care Table H, the Pennsylvania DHS Physician Procedure Codes schedule, Massachusetts MassHealth, and the Department of Labor OWCP anesthesia fee schedule all list 3 base units for this code.

By contrast, anesthesia reimbursement does not follow the RVU-based formula used for surgical CPT codes. Instead, it uses the standard anesthesia billing formula:

Time units are typically calculated at 1 unit per 15 minutes, though some payers use different intervals. As a result, always verify the conversion factor with the specific payer for the applicable fee schedule year, as this figure changes annually and varies significantly between Medicare, Medicaid programs, and commercial carriers. Additionally, use the FastRVU 2026 RVU lookup tool to cross-reference Medicare base unit values and confirm the current conversion factor for your locality.

Practices managing multiple anesthesia providers or high-volume orthopedic caseloads can reduce calculation errors by centralizing time-unit tracking. For example, Pabau’s claims management software helps practices flag modifier and formula discrepancies before claim submission, reducing rework at the clearinghouse level.

Anesthesia modifiers that apply to CPT code 01390

Modifier selection for 01390 depends on who is providing and supervising the anesthesia. Medicare and most commercial payers require one of the following qualifying modifiers on every anesthesia claim. Specifically, using the wrong modifier, or omitting it entirely, is one of the most common denial triggers for this code range.

In addition, physical status modifiers (P1 through P6) add modifying units to the formula. P3 (patient with severe systemic disease) adds 1 unit; P4 adds 2; P5 adds 3. P6 (brain-dead patient for organ donation) is not separately reimbursed by most payers. Therefore, always attach the correct physical status modifier in addition to the qualifying modifier.

Review AAPC Codify for current modifier pairing guidelines and payer-specific modifier requirements that may differ from the Medicare default rules shown above.

ICD-10 diagnosis codes that pair with CPT code 01390

CPT 01390 does not stand alone. Every anesthesia claim requires a diagnosis code that supports medical necessity for the procedure performed. The ICD-10-CM codes most commonly paired with 01390 reflect the fracture, injury, or condition at the upper ends of the tibia, fibula, or patella. Accurate paired ICD-10 diagnosis codes are essential for claim adjudication. Furthermore, using a non-specific or mismatched diagnosis is a leading cause of medical necessity denials in anesthesia billing.

Use the seventh-character extension correctly: “A” for the initial encounter, “D” for subsequent encounter, and “S” for sequela. For instance, payers routinely audit extension inconsistencies, particularly when a subsequent encounter code appears on what should be an initial claim. As a result, verify code specificity using the CDC/NCHS ICD-10-CM web tool for the applicable fiscal year’s code set.

CPT code 01390 vs. adjacent codes in the knee and popliteal area

Selecting the wrong adjacent code is the most costly coding error in the 01380-01404 range. The distinction between closed and open approaches, and between joint-level vs. bone-level procedures, drives code selection. Similarly, understanding ICD-10 coding accuracy principles applies equally when cross-walking to adjacent CPT anesthesia codes.

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The most consequential distinction is between 01390 and 01392. Both codes cover the same anatomical region (upper tibia, fibula, and/or patella), but 01392 applies when the approach is open. Consequently, billing 01390 when the operative report describes an open approach is a coding error that may constitute underbilling. Similarly, the reverse (billing 01392 for a closed procedure) is overbilling. Both expose the practice to audit risk.

For additional context, review the anesthesia-specific guidelines in the AMA CPT codebook’s introductory anesthesia section for more detailed CPT coding guidance for allied health and outpatient anesthesia billing workflows.

Payer policies and documentation requirements for CPT code 01390

Medicare

Medicare reimburses anesthesia using the base unit value established in the CMS Physician Fee Schedule. The conversion factor changes annually. Therefore, verify the current year’s conversion factor via the CMS Physician Fee Schedule lookup tool. Additionally, Medicare requires the AA, QK, QX, QY, QZ, or AD qualifier modifier on every claim.

Medicare also applies Medically Unlikely Edits (MUEs) to anesthesia codes. Similarly, for 01390, time units must reflect actual documented anesthesia time, verified against the anesthesia record. As a result, inflated time units without documentation are a common target in anesthesia audits.

Medicaid

In contrast, Medicaid anesthesia policies vary by state. New York eMedNY lists 01390 with place of service codes 21 (inpatient facility) and 24 (ambulatory surgery center). Pennsylvania DHS confirms the same POS options with PVR types 31 and 32. However, always consult the applicable state Medicaid provider manual for current coverage rules, prior authorization requirements, and conversion factors. Some state Medicaid programs use a fixed conversion factor that differs from Medicare.

Workers’ compensation

The Department of Labor OWCP fee schedule lists 01390 at 3 base units, consistent with other government payers. Similarly, workers’ compensation billing rules vary by state jurisdiction. Some states follow the DOL schedule; others use state-specific fee schedules. As a result, practices handling sports medicine billing under workers’ compensation should verify the applicable jurisdiction’s anesthesia conversion factor before finalizing claims.

Documentation requirements

Every claim for CPT code 01390 requires supporting documentation that establishes medical necessity and confirms the anesthesia was appropriate for the encounter. Specifically, required elements typically include:

• Anesthesia record: start and stop times, anesthetic agents used, patient monitoring data
• Operative note: confirms closed approach, named procedure, anatomical site (tibia, fibula, and/or patella)
• Pre-anesthesia evaluation: documents ASA physical status classification
• Post-anesthesia note: patient status at transfer to recovery
• Diagnosis linkage: ICD-10 code(s) clearly supported by clinical documentation

The anesthesia record is the primary audit target. In particular, missing start/stop times, or times that conflict with the OR log, are among the most frequent findings in anesthesia compliance reviews.

Place of service and billing context for CPT code 01390

CPT code 01390 is billed in facility settings. Specifically, the two valid place of service codes confirmed by multiple state Medicaid manuals are:

• POS 21: Inpatient hospital
• POS 24: Ambulatory surgery center (ASC)

01390 is not typically billed in an office setting (POS 11). Closed reductions of proximal tibia, fibula, or patella fractures require controlled anesthetic environments. As a result, payers will flag office-based billing for this code as a potential error.

For practices using CPT code documentation requirements as a model for other specialties, the anesthesia documentation standard is comparable: every billed service needs a complete record with timed entries and a linking diagnosis. For example, use the PGM Billing CPT search tool to cross-reference 01390 with payer-specific coverage indicators before submitting claims across multiple carriers.

Practices handling high volumes of musculoskeletal anesthesia cases can benefit from structured claim review workflows. Similarly, Pabau’s specialized CPT code billing resources illustrate how consistent documentation templates reduce the error rate across complex code sets. Furthermore, for centralized billing workflows, anesthesia fee schedule references from multiple payer sources help practices maintain current conversion factors without manual lookups before each submission.

Conclusion

In summary, CPT code 01390 is a precise code with clear clinical boundaries: closed approach, upper ends of the tibia, fibula, and/or patella, 3 base units. The most common errors are approach misclassification (billing 01390 for an open case or 01392 for a closed case), furthermore, missing or incorrect qualifier modifiers, and inadequate anesthesia record documentation for time units.

As a result, practices that standardize their claim review process, including modifier verification, time-unit calculation, and ICD-10 linkage checks, see fewer denials and faster adjudication. Specifically, Pabau’s claims management software is built to support exactly this kind of pre-submission workflow for orthopedic and anesthesia billing teams. To see how Pabau handles anesthesia and procedure code billing in practice, book a demo.

Continue your research

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