2026 ICD-10-CM Diagnosis Code M85.071Fibrous dysplasia (monostotic), right ankle and foot

ICD-10-CM Codes›M00–M99›M80-M85›M85

ICD-10-CM M85.071
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M85.071 is a billable ICD-10-CM diagnosis code for fibrous dysplasia (monostotic), right 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 553 through 554. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified bone disease and musculoskeletal deformities.

Code Identity

ICD-10-CM Code
M85.071
Billable Status
Yes — Valid for Submission
Code Describes
Fibrous dysplasia (monostotic), right ankle and foot
Short Description
Fibrous dysplasia (monostotic), right ankle and foot
Same as the full description in the CMS dataset.
Parent Code
M85.07
Fibrous dysplasia (monostotic), ankle and foot

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM80-M85Disorders of bone density and structure
CategoryM85Other disorders of bone density and structure
This CodeM85.071Fibrous dysplasia (monostotic), right ankle and foot

Clinical ClassificationClinical

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

CCSR MUS028
Other specified bone disease and musculoskeletal deformities
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Ankle Injuries and Disorders

Your ankle bone and the ends of your two lower leg bones make up the ankle joint. Your ligaments, which connect bones to one another, stabilize and support it. Your muscles and tendons move it.

Read the full article at MedlinePlus

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

Convert M85.071 to ICD-9-CMHistory

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

ICD-9-CM
733.29 Bone cyst 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 M85.071Overview

Is M85.071 (Fibrous dysplasia (monostotic), ankle and foot) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report fibrous dysplasia (monostotic), right ankle and foot on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M85.071 group to?

When fibrous dysplasia (monostotic), right ankle and foot is the principal diagnosis on an inpatient stay, it groups to MS-DRG 553, 554, with relative weights from 0.8301 to 1.2963 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M85.071?

Under the General Equivalence Mappings, fibrous dysplasia (monostotic), right ankle and foot converts to ICD-9-CM 733.29 (bone cyst NEC). 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.