Arthroscopy · Knee

Open arthrotomy of the knee for exploration, drainage of infection, or removal of a foreign body or loose material from the joint space.

Verified May 8, 2026 · 5 sources ↓

Medicare: $689.06
Total RVUs: 20.63
Global, days: 90
Region: Knee

Drawn from CMSAAPCCgsmedicareMdclarity

Documentation requirements

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

Source · Editorial brief grounded in 5 cited references ↓

Preoperative imaging or lab values (e.g., joint aspirate WBC, ESR, CRP) supporting the indication for open exploration
Operative note naming the specific surgical approach used to access the joint (e.g., medial parapatellar, lateral)
Intraoperative findings documented explicitly — purulence, foreign body, loose body, or hematoma — not generic 'exploration'
Laterality of the operative knee (left or right) recorded in both the operative note and on the claim
Medical necessity rationale explaining why open arthrotomy was chosen over arthroscopic or percutaneous approach
Post-procedure plan and any cultures, specimens, or materials sent to pathology or microbiology

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 52 Reduced services 58 Staged or related 59 Distinct service 62 Co-surgeons 73 Discontinued pre-anesthesia 74 Discontinued post-anesthesia 76 Repeat, same physician 77 Repeat, another physician 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 5 cited references ↓

CPT 27310 describes an open knee arthrotomy performed to explore the joint cavity — typically to drain septic arthritis, evacuate a hemarthrosis, or retrieve a foreign body or loose osteochondral fragment that cannot be addressed arthroscopically. The surgeon incises through the joint capsule, directly visualizes the intra-articular space, performs the necessary intervention, and closes the wound. This is an open procedure; arthroscopic knee explorations or lavage are coded separately.

The 90-day global period means all routine postoperative care — wound checks, dressing changes, suture removal, and related office visits — is bundled through day 90. Any E/M visit during that window for a new or unrelated problem requires modifier 24. A staged or planned related procedure in the global period uses modifier 58; an unplanned return to the OR for a related complication uses modifier 78; an unrelated OR procedure during the global uses modifier 79.

Medical necessity documentation is the primary audit target for 27310. Payers expect imaging, lab values (ESR, CRP, joint aspirate results), or operative findings that justify open exploration over a less invasive approach. Operative notes must name the specific pathology encountered and addressed — vague notes citing 'joint exploration' without documented findings are the leading reason for post-payment audit recoupment.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	9.75
Practice expense RVU	8.83
Malpractice RVU	2.05
Total RVU	20.63
Medicare national rate	$689.06
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	$689.06
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 27310 get rejected.

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

Operative note lacks specific intraoperative findings — 'joint explored' without naming pathology triggers medical necessity denial
Missing laterality on the claim form; payers require LT or RT modifier for unilateral knee procedures
Upcoding or undercoding confusion with arthroscopic exploration codes; payers flag 27310 if procedure description suggests arthroscopic technique
Insufficient preoperative workup documentation to support medical necessity of open approach over less invasive alternatives
Global period conflicts when a related E/M or procedure is billed without the correct modifier (24, 58, 78, or 79) during the 90-day window

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01Is 27310 ever billed with an arthroscopic knee code on the same day?

Rarely appropriate. If the procedure starts arthroscopically and is converted to open, bill only the open code (27310). Billing both together without a modifier 59 and distinct documentation of separate anatomic sites will trigger an NCCI bundling denial. Verify the specific edit pair in the CGS NCCI PTP lookup before submitting both.

02What modifier do I use if the surgeon returns to the OR within the 90-day global to re-irrigate the same knee for a persistent infection?

Use modifier 78 — unplanned return to the OR for a related procedure during the global period. The return must be unplanned and related to the original procedure. If the return was staged and planned at the time of the first surgery, modifier 58 applies instead.

03Can 27310 be billed bilaterally?

Yes, if both knees are explored during the same operative session. Append modifier 50 for bilateral billing, or submit two line items with LT and RT if your payer requires that format. Document separate indications and findings for each knee in the operative note.

04Does 27310 require prior authorization from most commercial payers?

Most payers require prior authorization for elective open knee procedures. Emergent cases (e.g., septic joint requiring urgent washout) typically qualify for retroactive authorization, but the medical record must clearly document urgency. Check each payer's individual policy — authorization rules vary significantly.

05What ICD-10 diagnoses most commonly support 27310?

Septic arthritis of the knee (M00.061–M00.062), hemarthrosis (M25.061–M25.062), and presence of a foreign body in the knee joint are the primary supporting diagnoses. Payers expect the diagnosis to align with an indication that requires open access — document why arthroscopy was not sufficient or safe given the clinical picture.

06If 27310 is performed in an ASC versus a hospital outpatient department, does the physician fee change?

The physician's professional fee is the same regardless of site — total RVUs under the CMS Physician Fee Schedule 2026 do not change by site. The facility payment differs significantly between ASC and HOPD settings; see the site of service comparison table on this page.

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 surgical approach by name, the specific intraoperative findings (purulence, foreign body, loose body, hematoma volume), laterality, and the medical decision-making rationale for open versus arthroscopic access — all from the surgeon's dictation. That specificity closes the documentation gap that drives medical necessity denials and audit recoupment on 27310.

See how Mira captures CPT 27310 documentation