2026 ICD-10-CM Diagnosis Code M86.279Subacute osteomyelitis, unspecified ankle and foot

ICD-10-CM Codes›M00–M99›M86-M90›M86

ICD-10-CM M86.279
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M86.279 is a billable ICD-10-CM diagnosis code for subacute osteomyelitis, unspecified ankle and foot. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 539 through 541. The code is flagged as an unspecified code, since codes identifying laterality exist in the same family. Coders also document this condition as subacute osteomyelitis of ankle. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Osteomyelitis.

Code Identity

ICD-10-CM Code
M86.279
Billable Status
Yes — Valid for Submission
Code Describes
Subacute osteomyelitis, unspecified ankle and foot
Short Description
Subacute osteomyelitis, unspecified ankle and foot
Same as the full description in the CMS dataset.
Parent Code
M86.27
Subacute osteomyelitis, ankle and foot

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM86-M90Other osteopathies
CategoryM86Osteomyelitis
This CodeM86.279Subacute osteomyelitis, unspecified ankle and foot

Code EditsBilling

Medicare Code Editor checks that affect claim validity for M86.279.

Unspecified codes
Unspecified codes exist in the ICD-10-CM classification for circumstances when documentation in the medical record does not provide the level of detail needed to support reporting a more specific code. However, in the inpatient setting, there should generally be very limited and rare circumstances for which the laterality (right, left, bilateral) of a condition is unable to be documented and reported. The following pages contain the list of unspecified ICD-10-CM diagnosis codes for which there is a more specific code to identify laterality (right, left, bilateral) within that code family.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Subacute osteomyelitis of ankle

Clinical ClassificationClinical

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

CCSR MUS002
Osteomyelitis
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Bone Infections

Like other parts of the body, bones can get infected. The infections are usually bacterial, but can also be fungal. They may spread to the bone from nearby skin or muscles, or from another part of the body through the bloodstream.

Read the full article at MedlinePlus

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

Convert M86.279 to ICD-9-CMHistory

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

ICD-9-CM
730.07 Ac osteomyelitis-ankle
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 M86.279Overview

Is M86.279 (Subacute osteomyelitis, ankle and foot) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report subacute osteomyelitis, unspecified ankle and foot on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M86.279 group to?

When subacute osteomyelitis, unspecified ankle and foot is the principal diagnosis on an inpatient stay, it groups to MS-DRG 539, 540, 541, with relative weights from 0.7715 to 1.9697 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M86.279?

Under the General Equivalence Mappings, subacute osteomyelitis, unspecified ankle and foot converts to ICD-9-CM 730.07 (ac osteomyelitis-ankle). 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.