Open surgical excision of a synovial cyst located in the popliteal space behind the knee, commonly known as a Baker's cyst.

Verified May 8, 2026 · 8 sources ↓

Medicare: $468.28
Total RVUs: 14.02
Global, days: 90
Region: Knee

Drawn from AAPCMdclarityGenhealthPayerpriceAbos

Documentation requirements

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

Source · Editorial brief grounded in 8 cited references ↓

Diagnosis of Baker's cyst confirmed clinically or by imaging, with notation of failed conservative treatment
Operative note specifying the posterior approach, cyst stalk or capsular communication identified and excised
Documentation of neurovascular structure preservation during popliteal dissection
If billed same-day with another knee procedure (e.g., TKA or arthroscopy), explicit notation of separate incision site and independent surgical indication
Post-op note confirming complete excision and closure technique used

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 51 Multiple procedures 58 Staged or related 59 Distinct service 76 Repeat, same physician 77 Repeat, another physician 78 Unplanned return — related 79 Unrelated during global LT Left side RT Right side 50 Bilateral procedure AS PA/NP/CNS assistant

What this code covers

Source · Editorial summary grounded in 8 cited references ↓

CPT 27345 covers the open removal of a synovial cyst from the popliteal space — the Baker's cyst excision most orthopedic surgeons perform after conservative measures (aspiration, physical therapy, intra-articular injection) have failed. The surgeon makes a posterior knee incision, dissects to the cyst, excises it at its stalk or communication point with the joint capsule, and closes in layers. The popliteal location requires careful dissection around neurovascular structures, which distinguishes this from simpler superficial cyst excisions.

The 90-day global period means all routine post-op care through day 90 is bundled — no separate office visits unless you append modifier 24 for a clearly unrelated condition. NCCI edits bundle common knee arthroscopy codes (e.g., 29881) with 27345 when performed on the same knee at the same encounter; overriding that bundle requires solid documentation of a distinct, separately indicated procedure and modifier 59. Billing 27345 alongside 27447 (TKA) on the same day is the highest-scrutiny scenario — payable only when the cyst is excised through a separate capsular incision documented explicitly in the operative note.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	5.94
Practice expense RVU	6.82
Malpractice RVU	1.26
Total RVU	14.02
Medicare national rate	$468.28
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	$468.28
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 27345 get rejected.

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

NCCI bundle with same-day arthroscopic knee codes (29880, 29881) without modifier 59 and supporting documentation
Bundling denial when billed with TKA (27447) and operative note lacks documentation of a separate capsular incision
Lack of documented conservative treatment failure prior to surgical excision
Missing laterality — payers require LT or RT on facility and professional claims to avoid rejection

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 8 cited references ↓

01Can 27345 be billed on the same day as TKA (27447)?

Yes, but only when the operative note explicitly documents that the Baker's cyst was excised through a separate capsular incision — not as an incidental part of the arthroplasty approach. Append modifier 59 to 27345 and expect payer scrutiny. Weak operative note language is the primary reason this combination is denied.

02Are knee arthroscopy codes bundled with 27345?

NCCI bundles 27345 with codes like 29881 when performed on the same knee at the same encounter. To unbundle, document a distinct, separately indicated procedure and append modifier 59. The AAPC forum note on this pairing reflects a real edit — do not assume open vs. arthroscopic means automatically separate.

03Does 27345 carry a global period, and what does that include?

27345 has a 90-day global period. That covers the day before surgery, the surgery itself, and all routine post-op visits through day 90. Separate E/M billing in that window requires modifier 24 (unrelated condition) or modifier 25 (same-day pre-op E/M, if a significant, separately documented problem was addressed).

04When is modifier 22 appropriate for 27345?

Use modifier 22 when the dissection is substantially more complex than typical — for example, a cyst with dense adhesions to popliteal vessels requiring prolonged or unusual dissection. Support it with operative note language quantifying the added time and complexity. Without that documentation, modifier 22 claims are routinely rejected.

05What ICD-10 code maps to this procedure?

M71.20 (Synovial cyst of popliteal space, unspecified knee), M71.21 (right), and M71.22 (left) are the primary diagnoses. Use the laterality-specific code and confirm it matches the LT or RT modifier on the claim.

06Is 27345 performed in the ASC or hospital outpatient setting?

Both settings are common. The procedure is performed in ASCs (POS 24) and on-campus outpatient hospital departments (POS 22). Site of service affects payment — see the Site of Service comparison table on this page for HOPD vs. ASC rates.

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 posterior approach, description of cyst dissection to its capsular origin, confirmation of complete excision, and any separate incision notation when performed alongside another knee procedure. This prevents the most common denial scenario: an operative note that documents cyst removal but fails to specify approach or a distinct incision, triggering automatic bundling with same-day arthroscopic or arthroplasty codes.

See how Mira captures CPT 27345 documentation