2026 ICD-10-CM Diagnosis Code M21.271Flexion deformity, right ankle and toes

ICD-10-CM Codes›M00–M99›M20-M25›M21

ICD-10-CM M21.271
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M21.271 is a billable ICD-10-CM diagnosis code for flexion deformity, right ankle and toes. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 564 through 566. Coders also document this condition as ankle joint deformity. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acquired deformities (excluding foot).

Code Identity

ICD-10-CM Code
M21.271
Billable Status
Yes — Valid for Submission
Code Describes
Flexion deformity, right ankle and toes
Short Description
Flexion deformity, right ankle and toes
Same as the full description in the CMS dataset.
Parent Code
M21.27
Flexion deformity, ankle and toes

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM21Other acquired deformities of limbs
This CodeM21.271Flexion deformity, right ankle and toes

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Ankle joint deformity
  • Bilateral flexion deformity of ankle joints
  • Bilateral flexion deformity of feet
  • Flexion deformity of joint of left ankle
  • Flexion deformity of joint of right ankle
  • Flexion deformity of joint of right foot

Clinical ClassificationClinical

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

CCSR MUS023
Acquired deformities (excluding foot)
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 M21.271 to ICD-9-CMHistory

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

ICD-9-CM
736.89 Oth acq limb deformity
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 M21.271Overview

Is M21.271 (Flexion deformity, ankle and toes) a billable code?

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

What MS-DRG does M21.271 group to?

When flexion deformity, right ankle and toes is the principal diagnosis on an inpatient stay, it groups to MS-DRG 564, 565, 566, with relative weights from 0.7493 to 1.5436 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M21.271?

Under the General Equivalence Mappings, flexion deformity, right ankle and toes converts to ICD-9-CM 736.89 (oth acq limb deformity). 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.