CPT code 01382: Anesthesia for diagnostic knee arthroscopy

Key Takeaways

CPT code 01382 covers anesthesia for diagnostic arthroscopic procedures of the knee joint only; therapeutic knee arthroscopy is billed under a different code, CPT 01400

The ASA assigns 01382 three base units, the figure that anchors the billing formula, not five

Modifier selection, AA, QZ, QX, or QK, determines how much Medicare pays and whether CRNA billing is independent or physician-directed

Pabau’s unified clinical record keeps the anesthesia note, physical status, and procedure documentation together, so a diagnostic-to-therapeutic conversion or a missing timestamp is easier to catch before the claim goes out

CPT code 01382 covers anesthesia for diagnostic arthroscopic procedures of the knee joint, three base units, nothing therapeutic folded in. Get that boundary wrong on the claim, and the payer usually notices before your billing team does.

The sections below work through what 01382 covers, how those three base units turn into a payment, and where the modifier and documentation mistakes actually happen.

CPT code 01382: what it covers, and what it doesn’t

CPT code 01382 is the anesthesia billing code for diagnostic arthroscopic procedures of the knee joint.

That’s the full official descriptor, word for word: anesthesia for diagnostic arthroscopic procedures of knee joint. It sits inside the CPT anesthesia section for Procedures on the Knee and Popliteal Area, the same family that includes closed knee-joint work (CPT 01380) and the open or surgical arthroscopic knee codes (CPT 01400, CPT 01402).

The word that matters most in that descriptor is diagnostic. CPT 01382 covers a scope done to look, not to fix. If the surgeon goes in to investigate a suspected meniscal tear, a ligament injury, or unexplained knee pain, and the procedure stays purely exploratory, that’s 01382.

The moment the surgeon does something therapeutic in the same session, a meniscectomy, a debridement, a chondroplasty, a ligament repair, the anesthesia code changes too. That case moves to CPT 01400, not 01382. This is the single most common coding error in this code family: 01382 does not cover therapeutic arthroscopy, no matter how many older references say otherwise.

Practice management software like Pabau keeps the operative note, the anesthesia record, and billing prep inside one unified clinical record, which makes it easier to catch a diagnostic-to-therapeutic conversion, or a missing timestamp, before the claim goes out rather than after a denial comes back.

Base units and the billing formula for 01382

The ASA Relative Value Guide assigns CPT code 01382 three base units, the same as CPT 01380 (closed knee-joint procedures), and one fewer than CPT 01400, the code for therapeutic and open knee-joint work.

Three base units puts diagnostic knee arthroscopy toward the lower end of anesthesia complexity, which tracks: it’s usually a short, low-risk case with a clean start and stop point.

Anesthesia’s billing structure is unlike most other CPT categories. Rather than a flat fee per procedure, a case like a therapeutic meniscectomy, billed under surgical CPT 29881, anesthesia CPT 01400, is paid using a formula built from base units, time, and a payer-specific conversion factor.

Diagnostic knee arthroscopy under 01382 uses the same formula, just with a different base-unit starting point.

The anesthesia billing formula

The standard formula is: (Base units + time units + qualifying units) x conversion factor = reimbursement

• Base units: 3 (ASA-assigned for 01382, fixed per procedure)
• Time units: 1 unit per 15 minutes of anesthesia time, start to finish. Some payers use 10-minute increments; verify with each payer.
• Qualifying units: added by physical status modifiers (P3 typically adds 1 unit, P4 adds 2, P5 adds 3; P1 and P2 add 0). Not every payer reimburses qualifying units.
• Conversion factor: a dollar-per-unit figure set by each Medicare Administrative Contractor (MAC) by locality. Rates vary by region and update annually.

Worked billing example: diagnostic knee arthroscopy

A patient classified as P2 undergoes a diagnostic knee arthroscopy (surgical CPT 29870). Anesthesia runs 45 minutes, start to finish.

Using an example locality conversion factor of $22.27 (the CY2026 national anesthesia conversion factor is $20.4976; actual locality rates vary, so verify against the CMS Physician Fee Schedule for your specific MAC):

Start and stop times are the most defensible line item in that formula. Shave two minutes off the record, or add two minutes that didn’t happen, and the time-unit count moves, which moves the reimbursement. It’s a small number that’s easy to get sloppy about, and just as easy for an auditor to catch.

Modifiers for CPT code 01382

Modifier selection isn’t optional on an anesthesia claim. Medicare requires a modifier on every anesthesia line to identify who provided the service and under what supervision model, and submitting 01382 without one is one of the more reliable ways to get it kicked back.

Provider-type modifiers

Physical status modifiers (P1-P6)

Physical status modifiers are appended to CPT 01382 alongside the provider-type modifier. They reflect patient acuity and, for P3 and above, may add qualifying units to the billing formula.

Confirm which payers reimburse qualifying units before billing; Medicare generally treats these modifiers as documentation only, but many commercial contracts pay extra for them. The pre-anesthesia evaluation form is where the physical status classification is first documented.

CRNA billing under CPT 01382

Whether a CRNA bills independently or under medical direction comes down to two things: state scope-of-practice law, and whether the facility has opted out of the Medicare physician supervision requirement.

In opt-out states, a CRNA performing anesthesia for a diagnostic knee arthroscopy uses modifier QZ and bills 100% of the allowed amount under their own NPI. In opt-in states, the CRNA submits with QX (directed) while the supervising anesthesiologist submits with QK, each receiving 50%.

Confirm the facility’s opt-out status with the MAC before billing; using QZ in an opt-in state is a compliance exposure, not just a billing one. Scope-of-practice rules vary by state, so always verify with current MAC guidance.

Keep anesthesia documentation and billing prep in one place

Pabau keeps the anesthesia record, physical status documentation, and procedure notes inside a single clinical record, so your billing team has what it needs before the claim goes out, not after a denial comes back.

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Documentation that keeps a 01382 claim clean: a before-you-submit checklist

Clean 01382 claims come from documentation built during the encounter, not reconstructed afterward. CMS’s anesthesia documentation requirements spell out what has to be in the record, and missing any one item is enough to turn a payable claim into a denial or an audit flag.

• Confirm the procedure actually stayed diagnostic. If the operative note documents any therapeutic step, a meniscectomy, debridement, or repair, the anesthesia code isn’t 01382 anymore.
• Pre-anesthesia evaluation: documented before the procedure; includes patient history, airway assessment, medication review, and ASA physical status classification.
• Anesthesia record (intraoperative): continuous monitoring data, drugs administered with doses and times, anesthesia technique (general, regional, MAC), and start/stop time.
• Start and stop times: the exact times anesthesia was induced and when patient care was transferred; these determine the time-unit count.
• Patient physical status: ASA P1 through P6 classification, documented with clinical rationale for P3 and above.
• Post-anesthesia note: patient condition at time of transfer from recovery, signed by the anesthesia provider.
• Provider identity and role: clear documentation of whether the anesthesiologist personally performed, medically directed, or medically supervised, since this determines modifier eligibility.

Practices documenting anesthesia encounters across disconnected systems, paper here, a separate EHR there, then a billing platform, carry the highest risk of a mismatch between what the record says and what the claim says. Connecting EHR and billing workflows inside one system removes a manual transcription step, and the errors that tend to ride along with it.

Common billing errors and claim denial reasons

Fee schedule pages and code lookups are everywhere. Denial-pattern analysis specific to 01382 is not, so here are the five reasons these claims actually get kicked back.

• Missing or wrong modifier: submitting 01382 with no modifier, or one that doesn’t match the provider’s actual role, is the single biggest cause of rejection. Medicare won’t process an anesthesia claim without a recognized modifier.
• Time unit miscalculation: rounding to the nearest 15-minute block when the payer actually uses 10-minute increments creates a small, systematic error on every claim. Check the increment per payer before submitting.
• Physical status mismatch: documenting P3 in the anesthesia record but billing P2 on the claim, or the reverse, creates a discrepancy that tends to trigger a review.
• Billing 01382 for a case that turned therapeutic: the surgeon starts a diagnostic scope, finds a tear, and fixes it in the same session, but the claim still goes out as 01382. It should have moved to 01400. This is the coding error that shows up most often in this code family, and it’s an easy one for a payer to catch by cross-checking the surgical CPT.
• Documentation that doesn’t support the claim: no pre-anesthesia evaluation, missing start/stop times, an unsigned post-anesthesia note. Any one gap can trigger a denial or an audit. Structured digital documentation that has to be completed before the encounter closes is the most reliable way to prevent these gaps at scale.

A secondary risk comes from NCCI edits. Build an NCCI edit check into the billing workflow before submission, to catch bundling conflicts between 01382 and the surgical procedure code on the same claim. CMS maintains the NCCI edit tables and updates them quarterly.

01382 reimbursement: Medicare, Medicaid, and commercial payers

Reimbursement for CPT code 01382 isn’t a single national number. Medicare Administrative Contractors (MACs) set locality-specific conversion factors, so a practice in San Francisco is paid a different amount per unit than one in rural Mississippi for the exact same claim.

Always pull the current figure from the CMS Physician Fee Schedule lookup for your specific MAC rather than relying on a prior year’s rate.

Commercial contracts negotiated as a percentage above Medicare mean the actual dollar-per-unit rate varies by contract, so tracking procedure-level reimbursement against expected rates, across payers, is how a practice catches an underpayment pattern before it becomes a real revenue problem.

Related CPT codes: 01380, 01400, and neighboring knee anesthesia codes

The boundary that actually matters in this code family is diagnostic versus therapeutic, not arthroscopic versus open, and getting it wrong is one of the cleaner billing errors to audit because the code descriptions are specific enough to check directly against the operative report.

The AAPC CPT code lookup is a useful reference for comparing the exact wording of neighboring codes side by side.

The most common crossover error in this family isn’t open versus arthroscopic, it’s diagnostic versus therapeutic. When the surgical CPT is 29870 (diagnostic knee arthroscopy), the anesthesia code is 01382.

When the surgical CPT falls in the 29871-29889 range, meniscectomy, debridement, chondroplasty, ligament work performed arthroscopically, the anesthesia code is 01400, even though the technique is still arthroscopic. Open knee surgery not otherwise specified also bills 01400. Total knee arthroplasty bills 01402 regardless of technique.

Review the surgical CPT on every claim before assigning the anesthesia code; it’s a two-second check that prevents a rework cycle with the payer. It’s also worth not confusing 01380 with the anatomically distinct CPT 01462, which covers closed procedures on the lower leg, ankle, and foot, a different part of the limb entirely.

How Pabau supports anesthesia billing documentation

Standalone code lookup tools, AAPC, FindACode, MDClarity, are useful for reference after the fact. The gap they leave is between the clinical record and the actual billing submission. Pabau keeps the anesthesia note, physical status documentation, and procedure details inside the same unified clinical record used for the encounter itself, so a diagnostic-to-therapeutic conversion, or a missing start time, is visible before the claim goes out, not after a denial comes back.

For practices running high volumes of knee arthroscopy, digital pre-anesthesia evaluation forms that require every mandatory field before the encounter closes make an incomplete record structurally harder to create in the first place. That’s a smaller thing than it sounds: most of the documentation gaps that trigger a denial are gaps a required field would have caught.

Conclusion

CPT code 01382 is one of the more straightforward anesthesia codes to bill correctly once the documentation holds up. Three base units, a well-understood time formula, and a defined modifier set mean the variables are manageable, as long as the case actually stayed diagnostic.

Where practices lose money is in time-unit errors, modifier mismatches, and a diagnostic case that quietly became therapeutic without the code changing to match.

If your practice bills knee arthroscopy anesthesia regularly, keeping the anesthesia record, physical status documentation, and procedure notes inside one clinical record, rather than split across paper, a separate EHR, and a billing platform, is the single change that catches the most preventable errors before they become denials.

See how Pabau’s clinical record works for anesthesia documentation if that gap sounds familiar.

Continue your research

Billing anesthesia for a therapeutic knee arthroscopy instead of a diagnostic one? CPT code 01400 covers the 4-base-unit code that applies once the procedure moves past diagnostic, meniscectomy, debridement, and similar work.

Coding anesthesia for a knee amputation instead? CPT 01404 walks through the 5-base-unit code for knee disarticulation, along with its own modifier and documentation rules.

Need the surgical side of a therapeutic knee arthroscopy? CPT code 29881 covers the meniscectomy code that pairs with anesthesia CPT 01400.

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