Surgical · Knee

Deep incision through the bone cortex of the femur or knee to drain an abscess or address osteomyelitis at that site.

Verified May 8, 2026 · 6 sources ↓

Medicare: $603.89
Work RVU: 8.41
Global, days: 90
Region: Knee

Drawn from AAPCGenhealthMdclarityFastrvuAbos

Documentation requirements

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

Source · Editorial brief grounded in 6 cited references ↓

Confirm cortical penetration explicitly — state that the bone cortex was opened with drill, osteotome, or equivalent instrument
Identify the anatomic site: femur (specify proximal, shaft, or distal) or knee (specify tibial plateau, distal femur, patella if applicable)
Document the underlying indication by name (osteomyelitis, bone abscess) with supporting culture, imaging, or clinical findings
Describe drainage volume and character (purulent, serous) and whether debridement of necrotic bone was performed
Record irrigation method and solution used (e.g., saline lavage volume) to support medical necessity
Note anesthesia type (general vs. regional) and that the procedure was performed in an operating room setting

Applicable modifiers

Modifiers commonly billed with this code.

Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual

22 Increased complexity 51 Multiple procedures 58 Staged or related 59 Distinct service LT Left side RT Right side 78 Unplanned return — related 79 Unrelated during global 80 Assistant surgeon AS PA/NP/CNS assistant

What this code covers

Source · Editorial summary grounded in 6 cited references ↓

CPT 27303 covers a deep surgical incision that penetrates the bone cortex of the femur or knee — performed to drain a bone abscess, decompress infected medullary space, or debride osteomyelitic bone that hasn't responded to antibiotics alone. The surgeon retracts soft tissue, opens the cortex with a drill or osteotome, drains purulent material, irrigates the cavity, and closes in layers. This is not a soft-tissue I&D — the cortex must be violated for the code to apply.

Distinguish 27303 from adjacent codes: 27301 covers deep soft-tissue abscess or hematoma drainage in the thigh or knee region without entering bone; 27310 is an arthrotomy for joint-space infection. If the procedure extends to partial bone excision (craterization or saucerization), 27360 may be more appropriate. Code selection hinges on operative note specificity about cortical entry.

The 90-day global period applies. Postoperative wound checks, dressing changes, and management of expected sequalae (including staged irrigation/debridement) within that window are bundled. A return to the OR for a related procedure — such as repeat debridement of the same osteomyelitic site — bills with modifier 78. An unrelated procedure in the global window uses modifier 79.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU vs. total RVU

The work RVU (8.41) is the surgeon's own effort — the figure physician pay and productivity targets are built on. The total RVU (18.08) adds practice overhead and malpractice, and is what drives the Medicare payment below.

Work RVU	8.41
Practice expense RVU	7.93
Malpractice RVU	1.74
Total RVU	18.08
Medicare national rate	$603.89
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	$603.89
HOPD (APC 5113) Hospital outpatient department	$3,342.87
ASC (PI J8) Ambulatory surgical center (freestanding)	$2,084.06

Common denial reasons

The recurring reasons claims for CPT 27303 get rejected.

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

Operative note describes soft-tissue I&D only — no documentation of cortical entry, so payer downcodes to 27301
ICD-10 diagnosis code does not support bone-level pathology (e.g., using a cellulitis code instead of osteomyelitis M86.x or bone abscess)
Procedure billed as outpatient office setting when clinical documentation and code description require OR-level facility
Missing or inadequate imaging or microbiology to establish medical necessity for surgical bone drainage over antibiotic therapy alone
Unbundling error: 27303 billed same-day as 27301 for the same anatomic site without modifier 59 or XS to distinguish the services

Frequently asked questions

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

01What separates 27303 from 27301?

27301 is drainage of a deep soft-tissue abscess, bursa, or hematoma in the thigh or knee region — bone is never entered. 27303 requires opening the bone cortex. If your operative note doesn't document cortical penetration, payers will downcode to 27301.

02Can 27303 and 27310 be billed together on the same day?

Generally no without a distinct-service modifier. 27310 is an arthrotomy for joint exploration and drainage; 27303 is cortical bone drainage. If both are genuinely performed at separate anatomic sites (e.g., bone abscess of distal femur and separate septic joint), append modifier 59 or XS to the secondary code and document each site distinctly in the operative note.

03A patient returns 3 weeks post-op for repeat debridement of the same osteomyelitic femur site — what modifier applies?

Modifier 78 — unplanned return to the OR for a procedure related to the original surgery within the 90-day global. Document that the return was unplanned and directly related to the index osteomyelitis. A planned staged debridement would use modifier 58 instead.

04Does the 90-day global include IV antibiotic management postoperatively?

No. The global period bundles routine post-op visits and wound care, not separately identifiable E/M services for medical management of osteomyelitis (e.g., infectious disease follow-up or IV antibiotic monitoring). Those visits bill with modifier 24 if provided by the operating surgeon.

05What ICD-10 codes are typically paired with 27303?

Osteomyelitis codes (M86.x series — specify acute, subacute, chronic, and laterality) and bone abscess are the primary pairings. Avoid non-specific infection or cellulitis codes; payers expect a diagnosis that clinically justifies opening bone cortex.

06Is modifier 50 appropriate if osteomyelitis affects both femurs?

Yes, if the procedure is performed bilaterally in the same operative session, modifier 50 applies. Document each site in the operative note. Alternatively, some payers prefer LT and RT on separate line items — confirm payer preference before submitting.

Sources & references

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

Mira Scribe

Mira's AI scribe captures the cortical entry method (drill vs. osteotome), anatomic site on the femur or knee, description of drained material, debridement extent, and irrigation details from dictation. That specificity prevents downcoding to 27301 — the most common denial trigger — by distinguishing a bone-cortex procedure from a soft-tissue-only drainage in the audit record.

See how Mira captures CPT 27303 documentation