2026 ICD-10-CM Diagnosis Code M61.559Other ossification of muscle, unspecified thigh

ICD-10-CM Codes›M00–M99›M60-M63›M61

ICD-10-CM M61.559
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M61.559 is a billable ICD-10-CM diagnosis code for other ossification of muscle, unspecified thigh. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Muscle disorders.

Code Identity

ICD-10-CM Code
M61.559
Billable Status
Yes — Valid for Submission
Code Describes
Other ossification of muscle, unspecified thigh
Short Description
Other ossification of muscle, unspecified thigh
Same as the full description in the CMS dataset.
Parent Code
M61.55
Other ossification of muscle, thigh

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM60-M63Disorders of muscles
CategoryM61Calcification and ossification of muscle
This CodeM61.559Other ossification of muscle, unspecified thigh

Clinical ClassificationClinical

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

CCSR MUS026
Muscle disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Bone Diseases

Your bones help you move, give you shape and support your body. They are living tissues that rebuild constantly throughout your life. During childhood and your teens, your body adds new bone faster than it removes old bone. After about age 20, you can lose bone faster than you make bone.

Read the full article at MedlinePlus

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

Convert M61.559 to ICD-9-CMHistory

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

ICD-9-CM
728.19 Muscular calcificat 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 M61.559Overview

Is M61.559 (Other ossification of muscle, thigh) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other ossification of muscle, unspecified thigh on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M61.559 group to?

When other ossification of muscle, unspecified thigh 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 M61.559?

Under the General Equivalence Mappings, other ossification of muscle, unspecified thigh converts to ICD-9-CM 728.19 (muscular calcificat 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.