Open knee arthrotomy with removal of synovial tissue from either the anterior or posterior compartment — not both.

Verified May 8, 2026 · 6 sources ↓

Medicare: $649.98
Total RVUs: 19.46
Global, days: 90
Region: Knee

Drawn from CMSAbosAAPCAAOS

Documentation requirements

What must appear in the operative or office note to support the claim.

Source · Editorial brief grounded in 6 cited references ↓

Specify compartment treated — anterior OR posterior; bilateral or combined anterior/posterior justifies a different code
Operative note must name the surgical approach (e.g., medial parapatellar, subvastus); 'standard approach' is insufficient for audit
Document the extent of synovial tissue excised and the clinical indication (e.g., inflammatory arthritis, pigmented villonodular synovitis, post-traumatic synovitis)
Confirm open arthrotomy technique; arthroscopic synovectomy maps to a different CPT family and must not be coded as 27334
If billing same-day with a separately payable procedure, document the distinct nature and medical necessity of each service in the operative report

Applicable modifiers

Modifiers commonly billed with this code.

Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual

22 Increased complexity 24 Unrelated E/M during global 25 Significant separate E/M 50 Bilateral procedure 51 Multiple procedures 58 Staged or related 59 Distinct service 62 Co-surgeons 78 Unplanned return — related 79 Unrelated during global 80 Assistant surgeon LT Left side RT Right side XS Separate structure

What this code covers

Source · Editorial summary grounded in 6 cited references ↓

CPT 27334 covers an open arthrotomy of the knee with synovectomy limited to either the anterior or the posterior compartment. The surgeon makes a direct incision, opens the joint capsule, and excises diseased or inflamed synovial membrane. When both compartments require synovectomy in the same session, report 27335 instead — that code explicitly covers anterior and posterior including the popliteal area.

The 90-day global period means all routine post-op care through day 90 is bundled. Unrelated E/M visits in that window need modifier 24; related E/M visits on the day of surgery need modifier 25 if a separately identifiable service was provided pre-operatively. If a same-day procedure triggers a CCI edit — as it does with 27488 — a modifier (59 or XS) is required, and you must document that the procedures were distinct.

This is an open procedure, not arthroscopic. If the surgeon performs a synovectomy arthroscopically, the correct code family is 29875 or 29876, not 27334. Conflating open and arthroscopic approaches is a common audit flag.

RVU & reimbursement

Component RVUs and Medicare national rate. Actual payment varies by GPCI locality.

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	8.96
Practice expense RVU	8.6
Malpractice RVU	1.9
Total RVU	19.46
Medicare national rate	$649.98
Global period	90 days

Payment by site of service

Medicare pays different rates by setting. HOPD typically pays substantially more than ASC for the same procedure.

Source · CMS OPPS Addendum B·ASC HCPCS payment rates·2026

Setting	Medicare rate (national)
Office (PFS non-facility) Procedure performed in physician's office	$649.98
HOPD (APC 5113) Hospital outpatient department	$3,342.87
ASC (PI A2) Ambulatory surgical center (freestanding)	$1,644.87

Common denial reasons

The recurring reasons claims for CPT 27334 get rejected.

Source · Editorial brief grounded in CMS NCCI edits, AAOS coding appeals, and cited references ↓

Wrong code selected when both anterior and posterior compartments were treated — should be 27335, not 27334
Arthroscopic synovectomy billed under 27334 instead of the appropriate arthroscopy code (29875/29876)
CCI bundling conflict when billed same-day with 27488 without a modifier to override the edit
Insufficient documentation of compartment treated or surgical approach flagged on post-payment audit
Global period violation — related E/M or procedure billed within the 90-day window without required modifier 24 or 78/79

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 6 cited references ↓

01What is the difference between 27334 and 27335?

27334 covers synovectomy of either the anterior or posterior compartment only. 27335 is used when both the anterior and posterior compartments — including the popliteal area — are addressed in the same session. Don't report both codes together for a single knee.

02Can 27334 be billed with 27488 on the same day?

These codes hit a CCI edit together. A modifier (59 or XS) is required to override the bundling edit, and your operative note must clearly document that the procedures were distinct and separately indicated.

03Is 27334 the right code for arthroscopic synovectomy?

No. 27334 is an open arthrotomy procedure. Arthroscopic synovectomy of the knee maps to 29875 (limited) or 29876 (major, two or more compartments). Using 27334 for an arthroscopic case is a miscode and an audit risk.

04What modifiers apply if this is performed bilaterally?

For professional claims, bill one line with modifier 50. For ASC facility claims, bill two lines — one with LT and one with RT, each with one unit of service, per CMS NCCI bilateral billing requirements.

05How does the 90-day global period affect post-op billing?

All routine post-operative care through day 90 is bundled into 27334's payment. Bill unrelated E/M visits in the global window with modifier 24. A return to the OR for a related complication uses modifier 78; an unrelated procedure uses modifier 79.

06What ICD-10 diagnoses are commonly paired with 27334?

Common diagnoses include rheumatoid arthritis of the knee (M05.861/M05.862), pigmented villonodular synovitis (M12.261/M12.262), and post-traumatic synovitis (M67.361/M67.362). The diagnosis must support the medical necessity of open synovectomy specifically.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

Mira AI Scribe

Mira's AI scribe captures the compartment treated (anterior vs. posterior), the surgical approach by name, the extent of synovial excision, and the clinical indication from dictation — preventing the most common audit flag of an operative note that fails to distinguish 27334 from 27335 or from arthroscopic alternatives.

See how Mira captures CPT 27334 documentation