Synovectomy of the extensor tendon sheath of the foot — surgical removal of the inflamed or diseased synovial lining surrounding an extensor tendon.

Verified May 8, 2026 · 6 sources ↓

Medicare: $481.64
Total RVUs: 14.42
Global, days: 90
Region: Foot & ankle

Drawn from MdclarityAAPCFindacodeGenhealthEmedny

Documentation requirements

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

Source · Editorial brief grounded in 6 cited references ↓

Specify which extensor tendon sheath was excised (e.g., extensor hallucis longus, extensor digitorum longus) — 'extensor tendon sheath' alone is insufficient for audit purposes.
Document the pathology driving the procedure: tenosynovitis, rheumatoid synovitis, infection, or other inflammatory diagnosis, with supporting pre-op imaging or prior conservative treatment.
Record the surgical approach: incision location, method of sheath exposure, extent of synovial membrane excised, and confirmation that the tendon itself was preserved.
Note anesthesia type (local, regional, or general) and patient positioning, as these support medical necessity and anesthesia coding accuracy.
Include failure of conservative treatment (e.g., corticosteroid injections, NSAIDs, physical therapy) to establish medical necessity, particularly for payers requiring stepwise documentation.

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 25 Significant separate E/M 51 Multiple procedures 52 Reduced services 58 Staged or related 59 Distinct service 78 Unplanned return — related 79 Unrelated during global 80 Assistant surgeon LT Left side RT Right side XS Separate structure

What this code covers

Source · Editorial summary grounded in 6 cited references ↓

CPT 28088 describes a synovectomy of the extensor tendon sheath in the foot. The surgeon opens the skin over the affected extensor tendon, excises the inflamed or pathologic synovial membrane from the tendon sheath, and closes the wound. The procedure addresses chronic inflammatory conditions — rheumatoid arthritis, tenosynovitis, or infectious synovitis — that have failed conservative management. It is the extensor-specific counterpart to 28086, which covers the flexor tendon sheath.

The 90-day global period means all routine post-op visits, wound checks, and suture removals through day 90 are bundled. Unrelated E/M services during that window require modifier 24; new problems addressed on the same day as a pre-op visit require modifier 25. If a concurrent procedure is performed and not subject to NCCI bundling, append modifier 59 or an X-modifier to establish distinct procedural identity.

Choosing between 28088 and adjacent codes is the most common coding decision here. Use 28086 for flexor sheath synovectomy. Use 28090 when excising a discrete lesion (ganglion, cyst) from the tendon, sheath, or capsule of the foot — 28090 is lesion-excision, 28088 is synovectomy of the sheath itself. Document which tendon is involved and confirm extensor involvement; operative notes that don't specify flexor vs. extensor create audit exposure.

RVU & reimbursement

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

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	3.88
Practice expense RVU	10.04
Malpractice RVU	0.5
Total RVU	14.42
Medicare national rate	$481.64
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	$481.64
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 28088 get rejected.

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

Wrong tendon sheath laterality — billing 28088 (extensor) when the operative note describes a flexor tendon sheath procedure that should be 28086.
Insufficient medical necessity documentation: payers deny when there's no documented failure of conservative therapy prior to surgical intervention.
Unbundling conflict when 28088 is billed same-day with 28090 without a modifier — coders must establish that a synovectomy and a separate lesion excision were truly distinct procedures on different structures.
Missing or non-specific ICD-10 diagnosis: claims paired with unspecified foot pain codes (M79.671/M79.672) instead of a specific inflammatory or synovial diagnosis draw scrutiny.
Global period violations: post-op E/M visits billed without modifier 24 during the 90-day global are auto-denied.

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 6 cited references ↓

01What's the difference between CPT 28088 and 28086?

28086 is synovectomy of the flexor tendon sheath; 28088 is synovectomy of the extensor tendon sheath. The operative note must specify which compartment was addressed — billing the wrong code based on an ambiguous note is a common audit finding.

02When should I use 28090 instead of 28088?

Use 28090 when the surgeon excised a discrete lesion (ganglion cyst, fibroma) from the tendon, tendon sheath, or capsule of the foot. Use 28088 when the procedure was a synovectomy — removal of the inflamed synovial lining of the extensor sheath — not excision of a focal mass.

03Can 28088 and 28086 be billed together on the same operative session?

Yes, if both flexor and extensor sheaths were independently addressed in the same foot during the same session. Append modifier 51 to the lower-valued code and document each synovectomy separately in the operative note with distinct anatomical descriptions.

04What ICD-10 codes pair well with 28088 for medical necessity?

Strong pairings include M65.271–M65.279 (calcific tendinitis of ankle and foot), M65.871–M65.879 (other synovitis and tenosynovitis, ankle and foot), and rheumatoid arthritis codes (M06.071–M06.079 for foot/ankle). Avoid defaulting to unspecified foot pain — payers flag that pairing.

05How does the 90-day global period affect post-op billing for 28088?

All routine follow-up through day 90 is bundled — no separate E/M codes. If you treat an unrelated condition during that window, use modifier 24 on the E/M. If a new unrelated procedure is performed, use modifier 79. A related return to the OR for a complication uses modifier 78.

06Is 28088 typically performed in an ASC or hospital outpatient setting?

Both are common. The procedure is appropriate for outpatient surgical centers, and the site of service affects reimbursement — see the Site of Service comparison on this page. The facility payment differential between HOPD and ASC is meaningful for case-costing decisions.

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 specific extensor tendon involved, the extent of synovial resection, the approach and incision location, and documented failure of prior conservative treatment — all from dictation. That prevents the two most common denials: wrong-sheath code selection (28086 vs. 28088) and missing medical necessity supporting the surgical decision.

See how Mira captures CPT 28088 documentation