2026 ICD-10-CM Diagnosis Code M21.231Flexion deformity, right wrist

ICD-10-CM Codes›M00–M99›M20-M25›M21

ICD-10-CM M21.231
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M21.231 is a billable ICD-10-CM diagnosis code for flexion deformity, right wrist. 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 bilateral flexion deformity of wrists. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acquired deformities (excluding foot).

Code Identity

ICD-10-CM Code
M21.231
Billable Status
Yes — Valid for Submission
Code Describes
Flexion deformity, right wrist
Short Description
Flexion deformity, right wrist
Same as the full description in the CMS dataset.
Parent Code
M21.23
Flexion deformity, wrist

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM21Other acquired deformities of limbs
This CodeM21.231Flexion deformity, right wrist

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Bilateral flexion deformity of wrists
  • Flexion deformity of joint of right wrist

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

Wrist Injuries and Disorders

Your wrist connects your hand to your forearm. It is not one big joint; it has several small joints. This makes it flexible and allows you to move your hand in different ways. The wrist has two big forearm bones and eight small bones known as carpals. It also has tendons and ligaments, which are connective tissues.

The full article covers:

  • What are the types of wrist injuries and disorders?
  • Who is at risk for wrist injuries and disorders?
  • What are the symptoms of wrist injuries and disorders?
  • How are wrist injuries and disorders diagnosed?
  • What are the treatments for wrist injuries and disorders?
  • Can wrist injuries and disorders be prevented?

Read the full article at MedlinePlus

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

Convert M21.231 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 M21.231Overview

Is M21.231 (Flexion deformity, wrist) a billable code?

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

What MS-DRG does M21.231 group to?

When flexion deformity, right wrist 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 M21.231?

Under the General Equivalence Mappings, flexion deformity, right wrist 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.