Arthroscopy · Knee

Arthroscopic surgical procedure on the knee performed specifically to treat infection, including joint lavage (washout) and drainage of infected material.

Verified May 8, 2026 · 7 sources ↓

Medicare: $491.33
Total RVUs: 14.71
Global, days: 90
Region: Knee

Drawn from CMSAAPCAetnaElitelearningPriorityhealth

Documentation requirements

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

Source · Editorial brief grounded in 7 cited references ↓

Pre-operative documentation of suspected or confirmed joint infection (e.g., joint aspirate results, elevated ESR/CRP, WBC, or positive culture)
Operative note explicitly stating infection as the indication — not osteoarthritis, not routine lavage
Description of all compartments entered, volume and character of irrigant used, and drainage established
Post-operative culture or intraoperative specimen submission documented if tissue or fluid was sent
Laterality clearly stated (left or right knee) in both the operative note and the order
For repeat procedures within the 90-day global, documentation of clinical reason necessitating return to OR

Applicable modifiers

Modifiers commonly billed with this code.

Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual

22 Increased complexity 50 Bilateral procedure 52 Reduced services 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

What this code covers

Source · Editorial summary grounded in 7 cited references ↓

CPT 29871 describes a surgical knee arthroscopy performed to address an active joint infection. The surgeon introduces an arthroscope through small portals, visualizes the interior of the knee, irrigates the joint space to flush out infected fluid and debris, and establishes drainage. This is a definitive surgical intervention for septic arthritis or post-operative joint infection — not a diagnostic scope, and not a lavage for osteoarthritis.

The code carries a 90-day global period. That matters acutely with this diagnosis: septic joints often require repeat washouts. If the same surgeon performs a second arthroscopic irrigation and drainage during the global window because the infection persists or recurs, bill modifier 78 (return to OR for a related procedure during the global). If an unrelated procedure is performed during that window, use modifier 79. Documentation of the indication — confirmed or suspected infection with supporting labs, cultures, or clinical findings — must be unambiguous to survive payer scrutiny.

CMS NCD 150.9 governs Medicare coverage for arthroscopic lavage. CPT 29871 is the code used to report the covered infection indication under that NCD. Non-covered indications — osteoarthritic lavage alone, debridement for pain-only osteoarthritis, debridement and lavage for severe OA — are explicitly excluded. Some commercial payers, including Aetna, also exclude 29871 when the documented indication is arthroscopic lavage rather than confirmed infection. Lock down the diagnosis and operative note language before billing.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	6.52
Practice expense RVU	6.84
Malpractice RVU	1.35
Total RVU	14.71
Medicare national rate	$491.33
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	$491.33
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 29871 get rejected.

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

Indication documented as osteoarthritis or knee pain rather than confirmed or suspected infection — triggers NCD 150.9 non-coverage
Missing or inconclusive pre-operative infection workup (no aspirate, cultures, or inflammatory markers on record)
Repeat washout billed without modifier 78 during the 90-day global period
Laterality modifier (LT or RT) absent, causing claim rejection or payer edit
Commercial payer (e.g., Aetna) denying when operative note language supports lavage rather than infection treatment

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 7 cited references ↓

01Can 29871 be billed for osteoarthritis lavage under Medicare?

No. NCD 150.9 explicitly excludes arthroscopic lavage alone for the osteoarthritic knee. CPT 29871 is covered under that NCD only when the documented indication is infection. Billing it for OA lavage will result in denial.

02The patient needs a second washout two weeks after the first — how do I bill it?

Use modifier 78. The repeat procedure is a return to the OR for a complication or continuation of the original related condition (the infection) within the 90-day global. Modifier 78 signals an unplanned return for a related procedure and allows separate reimbursement at the intraoperative percentage.

03Does the diagnostic arthroscopy (29870) get billed separately when infection is found and washout is performed?

No. A diagnostic arthroscopy is always included in a surgical arthroscopy. If the scope starts as diagnostic and converts to surgical lavage and drainage, bill only 29871. Billing 29870 alongside 29871 on the same knee same session will be bundled and denied.

04Can 29866 or 29867 be reported with 29871 in the same session?

No. Per CPT guidelines and payer policy (including Priority Health), codes 29866 and 29867 should not be reported in conjunction with 29871 in the same session on the same knee.

05Is prior authorization typically required for 29871?

Yes for most commercial payers. Given that this is a surgical arthroscopy and infection cases may require urgent scheduling, confirm whether the payer has an urgent or emergent auth pathway. Some payers require clinical criteria review through utilization management programs before approval.

06What ICD-10 codes support 29871 billing?

Primary infection diagnoses drive coverage: M00.061–M00.062 (pyogenic arthritis, knee), M00.861–M00.862 (arthritis due to other organisms), and T84.5XXA/D/S series for post-procedural infection involving joint prosthesis if applicable. Avoid osteoarthritis (M17.x) as a primary diagnosis — it triggers NCD 150.9 exclusions.

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 confirmed infection indication, pre-op workup findings (aspirate results, inflammatory markers), intraoperative findings (character and volume of fluid, compartments visualized), irrigation volume, and drainage established — all from dictation. That prevents the most common denial: an operative note that describes lavage without clearly tying the procedure to a documented infectious indication under NCD 150.9.

See how Mira captures CPT 29871 documentation