2026 ICD-10-CM Diagnosis Code M90.561Osteonecrosis in diseases classified elsewhere, right lower leg

ICD-10-CM Codes›M00–M99›M86-M90›M90

ICD-10-CM M90.561
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M90.561 is a billable ICD-10-CM diagnosis code for osteonecrosis in diseases classified elsewhere, right lower leg. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 553 through 554. The code is a manifestation code that cannot be reported as the principal diagnosis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Aseptic necrosis and osteonecrosis.

Code Identity

ICD-10-CM Code
M90.561
Billable Status
Yes — Valid for Submission
Code Describes
Osteonecrosis in diseases classified elsewhere, right lower leg
Short Description
Osteonecrosis in diseases classd elswhr, right lower leg
Parent Code
M90.56
Osteonecrosis in diseases classified elsewhere, lower leg

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM86-M90Other osteopathies
CategoryM90Osteopathies in diseases classified elsewhere
This CodeM90.561Osteonecrosis in diseases classified elsewhere, right lower leg

Code EditsBilling

Medicare Code Editor checks that affect claim validity for M90.561.

Manifestation diagnoses
Manifestation codes describe the manifestation of an underlying disease, not the disease itself, and therefore should not be used as a principal diagnosis.

Clinical ClassificationClinical

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

CCSR MUS030
Aseptic necrosis and osteonecrosis
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Osteonecrosis

Osteonecrosis is a disease caused by reduced blood flow to bones in the joints. In people with healthy bones, new bone is always replacing old bone. In osteonecrosis, the lack of blood causes the bone to break down faster than the body can make enough new bone. The bone starts to die and may break down.

Read the full article at MedlinePlus

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

Convert M90.561 to ICD-9-CMHistory

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

ICD-9-CM
731.8 Bone involv in oth dis
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.
ICD-9-CM
733.49 Asept necrosis bone NEC
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.

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 M90.561Overview

Is M90.561 (Osteonecrosis in diseases classified elsewhere, lower leg) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report osteonecrosis in diseases classified elsewhere, right lower leg on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M90.561 group to?

On inpatient claims, osteonecrosis in diseases classified elsewhere, right lower leg maps to MS-DRG 553, 554, with relative weights from 0.8301 to 1.2963 depending on complications. Higher weights mean higher Medicare reimbursement.

Can M90.561 be a principal diagnosis?

No. This is a manifestation code: osteonecrosis in diseases classified elsewhere, right lower leg describes the manifestation of an underlying disease rather than the disease itself, so the underlying condition is sequenced first.

What is the ICD-9 equivalent of M90.561?

Under the General Equivalence Mappings, osteonecrosis in diseases classified elsewhere, right lower leg converts to ICD-9-CM 731.8 (bone involv in oth dis) and 733.49 (asept necrosis bone 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.