ICD-10-CM · Other

M67.28

Synovial membrane thickening or overgrowth at an anatomical site not captured by any other specific M67.2x subcode — used when the affected joint or tendon sheath falls outside the shoulder, elbow, wrist, hand, hip, knee, ankle, or foot designations.

Verified May 8, 2026 · 4 sources ↓

Status: Billable
Chapter: 13
Related CPT: 5
Region: Other

Drawn from CDCAAPCICD10DataCdek

Documentation tips

What should appear in the chart to support M67.28.

Source · Editorial brief grounded in 4 cited references ↓

Name the exact joint or tendon sheath affected (e.g., 'sternoclavicular joint synovial hypertrophy') so reviewers can confirm no site-specific subcode applies.
State laterality explicitly (right vs. left) in the assessment — M67.28 carries no built-in laterality character, and the claim may be pulled for medical review.
Record imaging findings that support synovial thickening: MRI signal change, ultrasound-confirmed synovial proliferation, or arthroscopic description of hypertrophied synovium.
Document that PVNS has been ruled out or is not suspected; if it hasn't, a pathology or MRI note to that effect protects against an Excludes1 conflict with M12.2–.
If conservative management preceded the encounter, note what was tried (NSAIDs, corticosteroid injection, physical therapy) and duration — supports medical necessity for any surgical or procedural intervention.

Related CPT procedures

Procedure codes commonly billed with M67.28. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

20600 $56.11

Needle aspiration and/or injection of a small joint or bursa — such as a finger or toe joint — performed without ultrasound guidance.

20605 $57.12

Aspiration and/or injection of an intermediate joint or bursa — such as the wrist, elbow, ankle, acromioclavicular joint, or olecranon bursa — performed without ultrasound guidance.

20610 $68.81

Aspiration and/or injection of a major joint or bursa (shoulder, hip, knee, or subacromial bursa) performed without ultrasound guidance.

27310 $689.06

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

29999 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M67.28 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

Assigning M67.28 when a site-specific M67.21–M67.27 code exists — always check the full subcategory before defaulting to 'other site.'
Using M67.28 when the pathology is actually pigmented villonodular synovitis (PVNS) — the Excludes1 note at M67.2 prohibits this combination; PVNS maps to M12.2–.
Selecting M67.29 (unspecified site) when the site is documented — payers treat unspecified codes as insufficiently specific and may deny or downcode.
Failing to append a laterality modifier or document side in the note, which can trigger medical review requests for joint-based procedure claims.
Confusing synovial hypertrophy with tendinitis NOS (M77.9–) — the M67 category Excludes1 makes these mutually exclusive; ensure the clinical finding is synovial membrane enlargement, not isolated tendon inflammation.

Clinical context

Source · Editorial summary grounded in 4 cited references ↓

M67.28 is the residual 'other site' code within the M67.2 synovial hypertrophy subcategory. Use it when the provider documents synovial hypertrophy or synovial thickening at a site for which no site-specific subcode exists — for example, the sacroiliac joint, sternoclavicular joint, acromioclavicular joint, or costovertebral joint. If the affected site maps to any of M67.21 through M67.27, use that more specific code instead.

The parent category M67.2 carries an Excludes1 note for villonodular synovitis (pigmented), coded under M12.2–. If imaging or pathology identifies pigmented villonodular synovitis (PVNS), do not assign M67.28 — pivot to the appropriate M12.2 code. The broader M67 category also excludes palmar fascial fibromatosis (M72.0), tendinitis NOS (M77.9–), and xanthomatosis localized to tendons (E78.2).

In orthopedic practice, M67.28 most commonly appears alongside procedure codes for joint aspiration, synovial biopsy, or arthroscopic synovectomy at less-common joint sites. Because the code has no laterality built into the 7th character, document side clearly in the note — payers may request the operative report to confirm site. If the site is genuinely unspecified, M67.29 (unspecified site) is available, but site should be documented whenever possible.

Sibling codes

Other billable codes under M67.2 (laterality / anatomic variants).

M67.20

Synovial hypertrophy, not elsewhere classified, unsp site

M67.29

Synovial hypertrophy, NEC, multiple sites

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 4 cited references ↓

01When does M67.28 apply instead of M67.29?

Use M67.28 when the provider names a specific joint or tendon sheath that falls outside the joints covered by M67.21–M67.27 (shoulder through foot). Use M67.29 only when the site is genuinely undocumented — that should be rare in an orthopedic setting.

02Can I use M67.28 for synovial hypertrophy of the sacroiliac joint?

Yes. The sacroiliac joint has no dedicated M67.2 subcode, so M67.28 is the correct assignment when the provider documents SI joint synovial hypertrophy or thickening.

03Does M67.28 cover pigmented villonodular synovitis at an 'other' site?

No. The Excludes1 note at M67.2 explicitly bars PVNS from this subcategory. If PVNS is confirmed or suspected, code from M12.2– regardless of site.

04Is M67.28 valid as a primary diagnosis for joint aspiration (CPT 20605 or 20610)?

It can support the procedure when the aspiration is performed to manage symptomatic synovial hypertrophy. Ensure the note documents the site, the clinical indication (pain, swelling, restricted motion), and that the joint size matches the aspiration CPT selected.

05Does M67.28 require a 7th character?

No. M67.28 is a 5-character code and is billable as written. Seventh-character extensions apply to injury codes (S-codes), not to M-category synovial disorder codes.

06Can M67.28 be coded alongside an inflammatory arthritis code?

Potentially, if the synovial hypertrophy is documented as a distinct finding separate from the underlying inflammatory condition. However, many inflammatory arthritis codes (e.g., rheumatoid arthritis) already encompass synovial involvement — check whether a combination code covers both before adding M67.28.

07What imaging language in the report best supports M67.28?

MRI reports describing 'synovial thickening,' 'synovial proliferation,' or 'pannus formation' at a joint not covered by M67.21–M67.27 directly support M67.28. Ultrasound findings of hypoechoic synovial tissue with increased vascularity on Doppler also support the diagnosis.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

01CDC ICD-10-CM Tabular List 2026 (FY2026, effective Oct 1, 2025)
02
aapc.com
https://www.aapc.com/codes/icd-10-codes/M67.28
03
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M65-M67/M67-/M67.28
04
cdek.pharmacy.purdue.edu
https://cdek.pharmacy.purdue.edu/icd10/M67.28/

Mira AI Scribe

Mira's AI scribe captures the specific joint or tendon sheath involved, laterality, and supporting imaging descriptors (MRI synovial thickening, ultrasound synovial proliferation, arthroscopic hypertrophied synovium) directly from the encounter note. This prevents a fallback to M67.29 (unspecified site), blocks an inadvertent Excludes1 clash with PVNS codes, and supplies the site documentation payers need when reviewing joint procedure claims.

See how Mira captures M67.28 documentation