Surgical reconstruction of a chronically dislocating patella, typically involving transfer of the patellar tendon insertion as a bone block to restore stable tracking.

Verified May 8, 2026 · 7 sources ↓

Medicare: $705.09
Total RVUs: 21.11
Global, days: 90
Region: Knee

Drawn from CMSAAPCFindacodeMdclarityAAOS

Documentation requirements

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

Source · Editorial brief grounded in 7 cited references ↓

Operative note must name the specific technique — tibial tubercle osteotomy with bone block transfer, not 'patellar stabilization procedure'
Document history of recurrent patellar dislocation with episode frequency and prior conservative management attempted
Specify laterality (left or right knee) in both the operative note and the diagnosis codes
Record intraoperative findings including patellar tracking assessment before and after tubercle transfer
If MPFL reconstruction is performed concurrently, document it explicitly — it is bundled under 27420 and must not be billed separately
Imaging (MRI or CT) supporting bony and soft-tissue pathology should be in the record before prior authorization is submitted

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 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

What this code covers

Source · Editorial summary grounded in 7 cited references ↓

CPT 27420 covers open reconstruction of a dislocating patella where the patellar tendon insertion is transferred as a bone block — a tibial tubercle transfer — to correct pathologic lateral tracking or recurrent dislocation. This is not a soft-tissue-only stabilization; the defining element is osseous transfer of the insertion site. When MPFL reconstruction is performed concurrently as part of the same patellar stabilization surgery, it is encompassed within 27420 and not separately billable.

The 90-day global period governs all routine post-op management. Any unrelated E/M service in that window needs modifier 24. A staged secondary procedure — for example, a planned return for contralateral knee reconstruction — requires modifier 58, which resets the global clock. An unplanned return to the OR for a related complication uses modifier 78; for an unrelated procedure, modifier 79.

Site of service matters here. HOPD and ASC facility payments differ substantially (see the Site of Service comparison on this page). Most payers require documented failure of conservative management and evidence of recurrent dislocation before authorizing the procedure. ICD-10 diagnosis code precision — distinguishing initial dislocation from recurrent, and laterality — directly affects authorization and clean-claim rates.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	10
Practice expense RVU	8.98
Malpractice RVU	2.13
Total RVU	21.11
Medicare national rate	$705.09
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	$705.09
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 27420 get rejected.

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

Medical necessity denial when conservative management (PT, bracing) is not documented as having failed prior to surgery
Unbundling denial if MPFL reconstruction is billed separately on the same date — it is included in 27420
ICD-10 mismatch: billing M22.0x (recurrent dislocation) when the claim reflects an acute or initial event code
Missing laterality modifier (LT or RT) triggering claim suspension or return-to-provider
Incorrect modifier use during the 90-day global — E/M services without modifier 24 denied as included in global

Frequently asked questions

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

01Is MPFL reconstruction separately billable when performed with 27420?

No. When MPFL reconstruction is performed as part of the same patellar stabilization surgery that includes a tibial tubercle transfer, it is bundled within 27420. Billing it separately will trigger an NCCI bundling denial.

02Can 27420 be billed bilaterally?

Yes. Append modifier 50 for bilateral same-session tibial tubercle transfer. Some payers require two line items with LT and RT instead — verify payer preference before submitting.

03What modifier applies if this is a staged second-side reconstruction during the global period of a prior knee procedure?

Use modifier 58. It signals a staged or related procedure planned at the time of the original surgery, resets the global period, and avoids the global-period bundling edit. Document the staged intent in the original operative note.

04What ICD-10 codes support medical necessity for 27420?

Recurrent dislocation of the patella (M22.0–) with correct laterality is the strongest primary diagnosis. Confirm the episode descriptor — recurrent versus initial dislocation — matches the clinical record. Payers routinely deny claims where the diagnosis code reflects an acute initial event rather than a recurrent or chronic instability pattern.

05Does the 90-day global period affect post-op PT or injection billing?

PT billed under a separate therapy provider is outside the global and not restricted. However, if the operating surgeon or their group bills an E/M visit for a post-op complaint related to the surgery, it is included in the global. Use modifier 24 only for a documented unrelated E/M service. Injections for an unrelated diagnosis during the global need modifier 79.

06When is modifier 22 appropriate for 27420?

Use modifier 22 when the procedure is substantially more complex than typical — for example, revision of a prior failed tibial tubercle transfer with hardware removal, significant scarring, or malalignment requiring additional osteotomy work. The operative note must quantify the added complexity and time. Expect a supporting letter request from the payer.

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 specific technique (tibial tubercle osteotomy, bone block dimensions, fixation method), laterality, intraoperative patellar tracking findings, and concurrent soft-tissue work from dictation. This prevents the two most common audit flags: an operative note that omits the osseous transfer detail — which auditors use to downcode or deny the reconstruction — and unbundling of a separately dictated MPFL repair that is included in 27420.

See how Mira captures CPT 27420 documentation