ICD-10-CM · Other

M65.08

Abscess of tendon sheath occurring at a site not individually classified elsewhere in the M65.0 subcategory — a pyogenic or septic infection of the tendon sheath at anatomical locations other than finger, thumb, or foot.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 10
Region: Other

Drawn from CDCICD10DataCMSAAPC

Documentation tips

What should appear in the chart to support M65.08.

Source · Editorial brief grounded in 5 cited references ↓

Specify the exact anatomical site of the abscess (e.g., 'tendon sheath abscess of the extensor carpi radialis at the wrist') — M65.08 requires the site to fall outside finger, thumb, and foot; ambiguous documentation may trigger audit queries.
Document laterality explicitly (right vs. left) in the provider note; M65.08 does not carry a laterality character, but payers and surgical CPT codes require side-specific documentation and modifiers.
Record the mechanism or presumed etiology — puncture wound, hematogenous spread, post-injection — because this drives additional diagnosis codes and justifies the level of care.
Include imaging findings (ultrasound showing fluid-filled tendon sheath, MRI confirming abscess loculation) or OR/aspiration findings that confirm abscess versus simple tenosynovitis, since the two carry different codes.
Document organism identification from wound culture or blood culture to support secondary organism codes (B95–B96 range) required for complete coding.

Related CPT procedures

Procedure codes commonly billed with M65.08. 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.

20610 $68.81

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

73070 $29.39

Radiographic examination of the elbow joint using a minimum of 2 views to evaluate bone structure and surrounding tissues.

73080 $33.07

Radiologic examination of the elbow, complete, requiring a minimum of three views.

73100 $34.40

Radiologic examination of the wrist with a minimum of two views.

73110 $42.75

Radiologic examination of the wrist, complete, requiring a minimum of three views

73130 $38.08

Radiographic examination of the hand requiring a minimum of three views.

20000 View procedure details

20005 View procedure details

27370 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M65.08 and adjacent codes.

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

Defaulting to M65.08 when a more specific M65.0x site code actually exists — verify finger (M65.04x), thumb (M65.02x), and foot (M65.07x) before assigning the 'other site' residual code.
Confusing abscess of tendon sheath (M65.08) with non-infectious tenosynovitis (M65.8x or M65.9) — the provider must explicitly document infection or abscess; 'swelling around tendon' alone does not support M65.08.
Omitting the causative organism code when culture results are in the chart — incomplete coding leaves reimbursement and clinical specificity on the table.
Assigning M65.08 for a post-procedural tendon sheath infection without first considering a procedure-complication code (T80–T88 range), which may be required as the principal diagnosis.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

M65.08 is the catch-all billable code for tendon sheath abscesses arising at sites outside the specifically enumerated locations in the M65.0 subcategory (which breaks out finger, thumb, and foot individually). Common anatomical targets captured here include the wrist, forearm, elbow, upper arm, shoulder girdle, and popliteal/posterior knee region. The condition typically presents as a fluctuant, tender, erythematous swelling along a tendon sheath with systemic or local signs of infection, and is often caused by direct inoculation from a puncture wound, hematogenous spread, or contiguous extension from adjacent osteomyelitis or septic arthritis.

Because M65.08 is a residual 'other site' code, its use is appropriate only after confirming no more specific M65.0x code applies to the documented location. If the abscess is at the finger (non-thumb), use M65.04x; if at the thumb, M65.02x; if at the foot, M65.07x. For abscess at the shoulder specifically, M65.08 is correct unless your encoder has an updated site-specific expansion — always verify against the current FY2026 tabular list.

Code additional causative organism when identified (e.g., B95.x for Staphylococcus, B96.x for other bacteria) per ICD-10-CM coding guidelines. If the abscess is a complication of a prior procedure, assign the appropriate complication code from T80–T88 as principal and link M65.08 as an additional descriptor only when instructed by guidelines. Surgical drainage (e.g., CPT 26020 for finger/palm tendon sheath; 20000/20005 for other soft-tissue abscess incision) and culture-directed antibiotic therapy are the standard treatment drivers for this encounter.

Sibling codes

Other billable codes under M65.0 (laterality / anatomic variants).

M65.00

Abscess of tendon sheath, unspecified site

Frequently asked questions

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

01What sites does M65.08 cover?

M65.08 covers tendon sheath abscesses at any anatomical site not individually classified in M65.0 — in practice, this most often means wrist, forearm, elbow, upper arm, shoulder, and knee/popliteal area. If the abscess is at the finger (non-thumb), thumb, or foot, use the corresponding site-specific M65.0x code instead.

02Does M65.08 require a laterality character?

No. M65.08 is a 5-character code with no 6th-character laterality extension in the current ICD-10-CM tabular list. However, document laterality in the clinical note because the paired CPT procedure code will require a RT or LT modifier for correct claim processing.

03Should I code the causative organism separately with M65.08?

Yes. ICD-10-CM instructs coders to assign an additional code from B95–B96 to identify the bacterial organism when it is documented. If culture identifies MRSA, add B95.62; for MSSA, add B95.61. Do not skip the organism code when it is available in the chart.

04How does M65.08 differ from M65.9 (synovitis and tenosynovitis, unspecified)?

M65.08 is specific to an infectious abscess of the tendon sheath — a pyogenic or septic process. M65.9 is a non-specific residual for inflammatory tenosynovitis without a documented infectious or abscess component. Using M65.9 when an abscess is documented is under-coding and may trigger a payer audit.

05Can M65.08 be used as a secondary code after a post-procedural infection code?

It depends on the clinical scenario. If a tendon sheath abscess arose as a direct complication of a procedure, the appropriate T-code complication code from T80–T88 should generally be sequenced first, with M65.08 potentially added for specificity if guidelines and your encoder support it. Follow ICD-10-CM Official Guidelines Section I.C.19 on complications of care.

06Which CPT codes most commonly pair with M65.08?

For soft-tissue abscess incision and drainage at sites captured by M65.08, CPT 20000 (superficial) and 20005 (deep) are common pairings. If joint aspiration or injection is also performed, 20600 or 20610 may apply. Imaging to confirm the abscess (ultrasound-guided drainage) may support additional radiology codes depending on payer policy.

07Is M65.08 valid for FY2026 billing?

Yes. M65.08 is a valid, billable diagnosis code in the FY2026 ICD-10-CM code set effective October 1, 2025, per the CDC ICD-10-CM Tabular List 2026. No deletion or revision is noted for this code in the FY2026 update cycle.

Sources & references

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

01CDC ICD-10-CM Tabular List 2026 (effective Oct 1, 2025)
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M65-M67/M65-/M65.08
03
cms.gov
https://www.cms.gov/Medicare/Coding/ICD10/Downloads/2019-ICD10-Coding-Guidelines-.pdf
04
cdc.gov
https://www.cdc.gov/nchs/icd/icd-10-cm/index.html
05
aapc.com
https://www.aapc.com/codes/icd-10-codes/M65

Mira AI Scribe

Mira's AI scribe captures the anatomical site of the tendon sheath abscess, laterality, mechanism of infection, relevant imaging or OR findings (e.g., ultrasound-confirmed fluid collection, purulent drainage at incision), and culture/organism data from the encounter note — ensuring M65.08 is supported by documented clinical criteria and that secondary organism codes are flagged automatically, preventing downcoding to a non-infectious tenosynovitis code or an audit flag for missing specificity.

See how Mira captures M65.08 documentation