2026 ICD-10-CM Diagnosis Code M86.359Chronic multifocal osteomyelitis, unspecified femur

ICD-10-CM Codes›M00–M99›M86-M90›M86

ICD-10-CM M86.359
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M86.359 is a billable ICD-10-CM diagnosis code for chronic multifocal osteomyelitis, unspecified femur. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Osteomyelitis.

Code Identity

ICD-10-CM Code
M86.359
Billable Status
Yes — Valid for Submission
Code Describes
Chronic multifocal osteomyelitis, unspecified femur
Short Description
Chronic multifocal osteomyelitis, unspecified femur
Same as the full description in the CMS dataset.
Parent Code
M86.35
Chronic multifocal osteomyelitis, femur

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM86-M90Other osteopathies
CategoryM86Osteomyelitis
This CodeM86.359Chronic multifocal osteomyelitis, unspecified femur

Code EditsBilling

Medicare Code Editor checks that affect claim validity for M86.359.

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.

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 M86.359 to ICD-9-CMHistory

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

ICD-9-CM
730.15 Chr osteomyelit-pelvis
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 M86.359Overview

Is M86.359 (Chronic multifocal osteomyelitis, femur) a billable code?

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

What MS-DRG does M86.359 group to?

When chronic multifocal osteomyelitis, unspecified femur 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 M86.359?

Under the General Equivalence Mappings, chronic multifocal osteomyelitis, unspecified femur converts to ICD-9-CM 730.15 (chr osteomyelit-pelvis). 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.