2026 ICD-10-CM Diagnosis Code M20.31Hallux varus (acquired), right foot

ICD-10-CM Codes›M00–M99›M20-M25›M20

ICD-10-CM M20.31
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M20.31 is a billable ICD-10-CM diagnosis code for hallux varus (acquired), right foot. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acquired foot deformities.

Code Identity

ICD-10-CM Code
M20.31
Billable Status
Yes — Valid for Submission
Code Describes
Hallux varus (acquired), right foot
Short Description
Hallux varus (acquired), right foot
Same as the full description in the CMS dataset.
Parent Code
M20.3
Hallux varus (acquired)

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM20Acquired deformities of fingers and toes
This CodeM20.31Hallux varus (acquired), right foot

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acquired forefoot adductus
  • Acquired hallux malleus
  • Acquired hallux malleus of left great toe
  • Acquired hallux malleus of right great toe
  • Acquired hallux varus
  • Acquired left hallux varus
  • Acquired right hallux varus
  • Acquired varus deformity of toe
  • Bilateral acquired hallux limitus of great toes
  • Bilateral acquired hallux malleus of great toes
  • Bilateral acquired hallux varus of great toes
  • Bilateral flexion deformity of feet
  • Varus deformities of feet
  • Varus deformity of great toe

Clinical ClassificationClinical

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

CCSR MUS021
Acquired foot deformities
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Hallux Varus

    displacement of the great toe (hallux) towards the midline or away from the other toes. it can be congenital or acquired.

Patient EducationClinical

Foot Injuries and Disorders

Each of your feet has 26 bones, 33 joints, and more than 100 tendons, muscles, and ligaments. No wonder a lot of things can go wrong. Here are a few common problems:

Read the full article at MedlinePlus

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

Convert M20.31 to ICD-9-CMHistory

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

ICD-9-CM
735.1 Hallux varus
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 M20.31Overview

Is M20.31 (Hallux varus (acquired)) a billable code?

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

What MS-DRG does M20.31 group to?

When hallux varus (acquired), right foot 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 M20.31?

Under the General Equivalence Mappings, hallux varus (acquired), right foot converts to ICD-9-CM 735.1 (hallux varus). 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.