Surgical revision of the patella (kneecap) without implantation of a prosthetic component — addressing misalignment, instability, or prior surgical complications through repositioning or structural correction.

Verified May 8, 2026 · 7 sources ↓

Medicare: $624.93
Total RVUs: 18.71
Global, days: 90
Region: Knee

Drawn from CMSAAPCMdclarityPayerpriceZimmerbiomet

Documentation requirements

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

Source · Editorial brief grounded in 7 cited references ↓

Specific patellar pathology documented (e.g., maltracking, instability, post-surgical complication) with clinical rationale for revision rather than initial procedure
Prior surgical history for the affected knee, including any previous patellar procedures that necessitate the revision
Intraoperative description of technique — name the approach and the corrective steps taken; 'standard revision' is not sufficient for audit
Confirmation that no prosthetic patellar component was implanted, distinguishing 27437 from patellar resurfacing codes
If billed with 27446 or other same-day knee codes, operative note must clearly delineate the distinct work supporting each separately reported code

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 50 Bilateral procedure 58 Staged or related 59 Distinct service 78 Unplanned return — related 79 Unrelated during global LT Left side RT Right side XS Separate structure

What this code covers

Source · Editorial summary grounded in 7 cited references ↓

CPT 27437 covers open surgical revision of the patella without prosthetic replacement. The procedure targets mechanical or structural failure of the kneecap — including malalignment, instability, or complications from a prior patellar procedure — and corrects the problem through repositioning or bony/soft-tissue work without placing an implant. It sits within the knee arthroplasty family but is distinct from patellar resurfacing or total knee arthroplasty.

The 90-day global period applies. That window covers the day-before visit, the procedure itself, and all routine follow-up through day 90. Unrelated E/M visits or procedures within that window require modifier 24 or 79 respectively. When 27437 is billed same-day with 27446 (unicompartmental arthroplasty), NCCI bundles the pair — modifier 59 or XS is required only when documentation clearly establishes distinct, separately identifiable work.

Most payers place this procedure in outpatient or ASC settings. Commercial rates vary materially by contract; see the Site of Service comparison for HOPD vs. ASC payment figures rendered on this page. Documentation of the specific patellar pathology, the prior surgical history, and the intraoperative technique used is essential for medical necessity review.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	8.71
Practice expense RVU	8.16
Malpractice RVU	1.84
Total RVU	18.71
Medicare national rate	$624.93
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	$624.93
HOPD (APC 5114) Hospital outpatient department	$7,413.38
ASC (PI A2) Ambulatory surgical center (freestanding)	$3,695.53

Common denial reasons

The recurring reasons claims for CPT 27437 get rejected.

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

NCCI bundle conflict when 27437 is billed with 27446 without modifier 59 or XS and supporting documentation of distinct procedural work
Medical necessity denial when operative note fails to document the specific patellar pathology or why conservative management was exhausted
Global period violation when a related post-op visit or same-surgeon procedure is billed within the 90-day window without the correct modifier (24, 78, or 79)
Incorrect site modifier (LT/RT missing or reversed) causing automated claim rejection at payers that require laterality on unilateral knee procedures
Upcoding flag when 27437 is billed alongside resurfacing or implant codes without clear documentation that no prosthesis was placed

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 7 cited references ↓

01What distinguishes 27437 from patellar resurfacing performed as part of a total knee arthroplasty?

27437 is a standalone patellar revision without a prosthetic implant. Patellar resurfacing during TKA is included in 27447 and is not separately reportable. If you placed a patellar component, 27437 is the wrong code.

02Can 27437 and 27446 be billed together on the same date?

NCCI bundles 27437 with 27446. You can append modifier 59 or XS to 27437 — but only when the operative note documents clearly distinct, separately identifiable work. Modifier 51 alone will not break the bundle edit.

03What modifier is required when 27437 is performed during the global period of a prior knee procedure for a related complication?

Use modifier 78 (unplanned return to the OR for a complication related to the original procedure). Do not use modifier 79 — that is for unrelated procedures during a global period.

04Is 27437 typically performed in an ASC or HOPD setting?

Both settings are used. PayerPrice data identifies place of service 22 (on-campus outpatient hospital) and 24 (ASC) as most common. The HOPD and ASC facility payments differ significantly — see the Site of Service comparison on this page.

05Does the 90-day global period affect billing for post-op physical therapy or unrelated visits?

PT billed by a separate provider is not subject to the surgeon's global. For the operating surgeon, unrelated E/M visits within the 90-day window need modifier 24 with documentation confirming the visit was unrelated to the surgery.

06When is modifier 22 appropriate on 27437?

When the procedure required substantially more physician work than typical — for example, severe adhesions from multiple prior surgeries, complex anatomy, or significantly prolonged operative time. The operative note must quantify the added complexity; a boilerplate 'increased difficulty' note will not support the modifier.

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 patellar pathology diagnosis, the prior surgical history driving the revision, the intraoperative technique including approach and corrective steps performed, and the explicit confirmation that no prosthetic component was implanted. That last point directly prevents downcoding disputes and payer requests to clarify whether resurfacing was performed — a frequent audit flag when 27437 is billed in proximity to arthroplasty codes.

See how Mira captures CPT 27437 documentation