CPT code 27330: Knee biopsy, open synovial tissue sampling2026 Medicare rate & RVUs in California
Open knee-joint biopsy code for obtaining synovial lining tissue when persistent synovitis or another intra-articular abnormality requires tissue diagnosis.
CMS doesn’t publish an office rate for 27330 in California.
Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.
Your location
On this page 9 sections
What 27330 covers
27330 represents open entry into the knee joint to obtain a sample of the synovial lining for diagnostic evaluation. An orthopedic surgeon may perform it when persistent, unexplained synovitis or another abnormal joint-lining change requires tissue examination, including evaluation for inflammatory or infectious disease. The specimen may be sent for histology or other laboratory analysis. This is an open biopsy, not an arthroscopic sampling procedure or removal of the joint lining.
Report the code when the operative service includes an arthrotomy to take a biopsy; the operative note should identify the knee, the abnormal tissue sampled, and the biopsy performed. The 90-day global period includes the day-before preoperative visit and 90 days of related postoperative care. When multiple procedures are performed in one session, the highest-valued procedure is paid in full and other procedures receive the standard multiple-procedure reduction. For bilateral procedures, modifier 50 is paid at 150%. Assistant-at-surgery payment is restricted, co-surgeon payment requires supporting documentation, and team surgery is not permitted.
This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.
Where 27330 pays more and less in California
The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.
29 of 29 payment localities
| Payment locality | Office | Facility |
|---|---|---|
| Bakersfield, CA | Unavailable | $422.25 |
| Chico, CA | Unavailable | $419.31 |
| El Centro, CA | Unavailable | $419.49 |
| Fresno, CA | Unavailable | $419.31 |
| Hanford, CA | Unavailable | $419.31 |
| Los Angeles, CA | Unavailable | $446.22 |
| Madera, CA | Unavailable | $419.31 |
| Marin County, CA | Unavailable | $495.71 |
| Merced, CA | Unavailable | $419.31 |
| Modesto, CA | Unavailable | $419.31 |
| Napa, CA | Unavailable | $472.75 |
| Oxnard, CA | Unavailable | $442.38 |
| Redding, CA | Unavailable | $419.31 |
| Rest of California | Unavailable | $419.31 |
| Riverside, CA | Unavailable | $430.81 |
| Sacramento, CA | Unavailable | $436.59 |
| Salinas, CA | Unavailable | $434.92 |
| San Benito County, CA | Unavailable | $507.71 |
| San Diego, CA | Unavailable | $442.77 |
| San Francisco, CA | Unavailable | $494.50 |
| San Luis Obispo, CA | Unavailable | $428.38 |
| Santa Clara County, CA | Unavailable | $502.74 |
| Santa Cruz, CA | Unavailable | $445.06 |
| Santa Maria, CA | Unavailable | $435.90 |
| Santa Rosa, CA | Unavailable | $449.30 |
| Stockton, CA | Unavailable | $419.31 |
| Vallejo, CA | Unavailable | $471.00 |
| Visalia, CA | Unavailable | $419.31 |
| Yuba City, CA | Unavailable | $419.31 |
How the 27330 rate is calculated
Each of 27330’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.
How the rate is built · 27330
RVUs × geographic indexes × conversion factor
Work4.98
4.98 RVUs× 1.000 GPCI
Practice expense6.31
6.31 RVUs× 1.000 GPCI
Malpractice1.07
1.07 RVUs× 1.000 GPCI
Adjusted RVUs
12.3600
Conversion factor
$33.4009
Medicare rate
$412.84
Every GPCI starts at 1.000, the national rate. Enter a ZIP or drag a slider.
Payment rules and modifiers for 27330
27330 has a 90-day global period: related visits in that window are included in the surgery payment.
CMS payment indicators · 27330
Knee biopsy, open synovial tissue sampling
| Rule | CMS value | What it means |
|---|---|---|
| Global period | 090 | Major surgery: the day before, the day of, and 90 days after are included. |
| Multiple procedures | 2 | Standard reduction: highest-valued procedure at 100%, others at 50%. |
| Bilateral (modifier 50) | 1 | Bilateral with modifier 50 pays 150% of the fee schedule amount. |
| Assistant at surgery (80/81/82/AS) | 1 | Not paid (statutory restriction). |
| Co-surgeons (62) | 1 | Permitted with supporting documentation. |
| Team surgery (66) | 0 | Not permitted. |
| Professional/technical | 0 | Physician service: no professional/technical split. |
| Split (54/55/56) | 0.10/0.69/0.21 | Share of the payment for pre-op, the procedure itself, and post-op care. |
Global surgery period · 27330
Knee biopsy, open synovial tissue sampling
90-day global period ends
Dec 30, 2026
Covers Sep 30, 2026 through Dec 30, 2026 (92 days, including the day before surgery).
Visit on Oct 31, 2026
Day 30 of the 90-day post-op period: related follow-up care is included in the surgical payment.
Pre-op dayGlobal period
What modifiers do to the payment
Modifier 50 · payment effect
With and without the modifier
27330 without 50 · national facility
$412.84
Knee biopsy, open synovial tissue sampling
27330-50 · Bilateral: 150%
$619.26
Both sides on one line with modifier 50 are paid at 150% of the fee schedule amount (subject to multiple-procedure rules with other procedures).
27330 compared with similar codes
Compare codes · National
4 codes, side by side
How to choose
- 29870Knee arthroscopyDiagnostic, with or without biopsy
- 27330 describes an open arthrotomy biopsy. Use the arthroscopy code when the surgeon obtains the synovial sample through an arthroscope.
- 27331Knee arthrotomyAnterior or posterior synovectomy
- 27330 is reported for open tissue sampling. 27331 describes an open knee procedure directed to exploration, drainage, or foreign-body removal.
- 27334Knee synovectomyAnterior or posterior approach
- 27330 removes a sample for diagnosis; 27334 is for open synovectomy, in which synovial tissue is removed therapeutically.
27330 billing questions
When should 27330 be chosen instead of an arthroscopic knee biopsy?
Use 27330 for an open arthrotomy performed to sample the knee lining. When the biopsy is obtained arthroscopically, consider the applicable arthroscopy code, such as 29870.
Does 27330 include the pathology examination?
The code represents obtaining the tissue through the open procedure. Histologic examination is a separate laboratory service when performed and reportable by the pathology provider.
What documentation supports reporting 27330?
Document the knee side, the reason tissue diagnosis was needed, the synovial or other intra-articular tissue sampled, and the open biopsy performed.
Can 27330 be reported bilaterally?
For a bilateral procedure, CMS pays 150% when modifier 50 is reported. The operative documentation should support biopsy of both knees.
How does the global period affect postoperative visits?
27330 has a 90-day global period. The day-before preoperative visit and 90 days of related postoperative care are included.
Where these rates come from
FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.
CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027
Show the CMS file lines behind this rate
Fee sheets
Put 27330 and the rest of your codes on one sheet
Your codes at your locality, with payer contracts beside Medicare.
Build my fee sheet