2026 ICD-10-CM Diagnosis Code M65.00Abscess of tendon sheath, unspecified site

ICD-10-CM Codes›M00–M99›M65-M67›M65

ICD-10-CM M65.00
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M65.00 is a billable ICD-10-CM diagnosis code for abscess of tendon sheath, unspecified site. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 557 through 558. Coders also document this condition as abscess of tendon. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Musculoskeletal abscess and Tendon and synovial disorders.

Code Identity

ICD-10-CM Code
M65.00
Billable Status
Yes — Valid for Submission
Code Describes
Abscess of tendon sheath, unspecified site
Short Description
Abscess of tendon sheath, unspecified site
Same as the full description in the CMS dataset.
Parent Code
M65.0
Abscess of tendon sheath

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM65-M67Disorders of synovium and tendon
CategoryM65Synovitis and tenosynovitis
This CodeM65.00Abscess of tendon sheath, unspecified site

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Abscess of tendon
  • Abscess of tendon of lower limb
  • Abscess of tendon of upper limb
  • Abscess of tendon sheath

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Abscess(connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic)
      • tendon (sheath)

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MUS027
Musculoskeletal abscess
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR MUS009
Tendon and synovial disorders
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Abscess

An abscess is a pocket of pus. You can get an abscess almost anywhere in your body. When an area of your body becomes infected, your body's immune system tries to fight the infection. White blood cells go to the infected area, collect within the damaged tissue, and cause inflammation. During this process, pus forms.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert M65.00 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
727.89 Synov/tend/bursa dis NEC
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About M65.00Overview

Is M65.00 (Abscess of tendon sheath) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report abscess of tendon sheath, unspecified site on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M65.00 group to?

When abscess of tendon sheath, unspecified site is the principal diagnosis on an inpatient stay, it groups to MS-DRG 557, 558, with relative weights from 0.8932 to 1.4869 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M65.00?

Under the General Equivalence Mappings, abscess of tendon sheath, unspecified site converts to ICD-9-CM 727.89 (synov/tend/bursa dis NEC). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.