2026 ICD-10-CM Diagnosis Code M61.171Myositis ossificans progressiva, right ankle

ICD-10-CM Codes›M00–M99›M60-M63›M61

ICD-10-CM M61.171
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M61.171 is a billable ICD-10-CM diagnosis code for myositis ossificans progressiva, right ankle. 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
M61.171
Billable Status
Yes — Valid for Submission
Code Describes
Myositis ossificans progressiva, right ankle
Short Description
Myositis ossificans progressiva, right ankle
Same as the full description in the CMS dataset.
Parent Code
M61.17
Myositis ossificans progressiva, ankle, foot and toe(s)

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM60-M63Disorders of muscles
CategoryM61Calcification and ossification of muscle
This CodeM61.171Myositis ossificans progressiva, right ankle

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 M61.171 to ICD-9-CMHistory

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

ICD-9-CM
728.11 Prog myositis ossificans
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 M61.171Overview

Is M61.171 (Myositis ossificans progressiva, ankle, foot and toe(s)) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report myositis ossificans progressiva, right ankle on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M61.171 group to?

When myositis ossificans progressiva, right ankle 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 M61.171?

Under the General Equivalence Mappings, myositis ossificans progressiva, right ankle converts to ICD-9-CM 728.11 (prog myositis ossificans). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.