Unlisted code for an open procedure on the femur or knee that has no specific CPT code.
- Medicare
- $0.00
- Work RVU
- 0
- Global, days
- Region
- Knee
Documentation requirements
What must appear in the operative or office note to support the claim.
Source · Editorial brief grounded in 2 cited references ↓
- Operative note with approach and structures treated
- Graft, implant, or biologic used, with lot or sticker
- Why no listed or Category III code applies
- Comparison code and reasoning
- Laterality and supporting imaging
- Prior authorization and payer policy reference
Applicable modifiers
Modifiers commonly billed with this code.
Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual
What this code covers
Source · Editorial summary grounded in 2 cited references ↓
27599 is the unlisted code for the femur and knee. It covers open or percutaneous procedures on the thigh and knee joint, including the patella and surrounding soft tissue, when nothing in the listed knee and femur codes fits. Knee arthroscopy procedures without a code go to 29999.
It gets used for newer cartilage restoration techniques, some osteotomy and ligament combinations, and procedures that are investigational for many payers. Before using it, check Category III codes and confirm the procedure is not a listed code with a different graft or fixation. A total knee done with robotic assistance is still 27447. The robot does not make it unlisted.
Medicare has no fee and a YYY global. Send the op note, cover letter, and a comparison code with similar work. Many commercial payers have specific policies on cartilage and biologic procedures and will deny 27599 as investigational unless the case fits their criteria. Get the authorization and the policy number in writing before scheduling.
RVU & reimbursement
Component RVUs and Medicare national rate. Actual payment varies by GPCI locality.
Source · CMS Physician Fee Schedule, RVU26A · January 2026
| Work RVU | 0 |
| Practice expense RVU | 0 |
| Malpractice RVU | 0 |
| Total RVU | 0 |
| Medicare national rate | $0.00 |
| Global period | 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 | $0.00 |
HOPD (APC 5111) Hospital outpatient department | $252.01 |
Common denial reasons
The recurring reasons claims for CPT 27599 get rejected.
Source · Editorial brief grounded in CMS NCCI edits, AAOS coding appeals, and cited references ↓
- Payer policy treats the procedure as investigational
- Arthroscopic procedure billed under open unlisted code
- Robotic or navigated listed procedure billed as unlisted
- No prior authorization
- Missing comparison code
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 2 cited references ↓
01When do I use CPT 27599?
02Is robotic knee replacement billed with 27599?
03Why are 27599 claims denied as investigational?
Sources & references
Editorial content was developed using the following public sources.
- 01CMS Physician Fee Schedule 2026
- 02cms.govhttps://www.cms.gov/regulations-and-guidance/guidance/manuals/downloads/clm104c12.pdf
Mira Scribe
Mira Scribe documents the graft or implant, side, and each step of the knee procedure, which supports payer review on cartilage and other unlisted cases.
See how Mira captures CPT 27599 documentation