2026 ICD-10-CM Diagnosis Code M20.42Other hammer toe(s) (acquired), left foot

ICD-10-CM Codes›M00–M99›M20-M25›M20

ICD-10-CM M20.42
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M20.42 is a billable ICD-10-CM diagnosis code for other hammer toe(s) (acquired), left 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. Coders also document this condition as acquired hammer toe of lesser toe of left foot. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acquired foot deformities.

Code Identity

ICD-10-CM Code
M20.42
Billable Status
Yes — Valid for Submission
Code Describes
Other hammer toe(s) (acquired), left foot
Short Description
Other hammer toe(s) (acquired), left foot
Same as the full description in the CMS dataset.
Parent Code
M20.4
Other hammer toe(s) (acquired)

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM20Acquired deformities of fingers and toes
This CodeM20.42Other hammer toe(s) (acquired), left foot

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acquired hammer toe of lesser toe of left foot
  • Acquired hammer toe of lesser toe of right foot
  • Acquired hammer toes of bilateral feet
  • Bilateral acquired hammer toe of lesser toe of feet
  • Bilateral flexion deformity of feet
  • Hammer 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

Patient EducationClinical

Toe Injuries and Disorders

Fourteen of the 26 bones in your feet are in your toes. The toes, particularly your big toe, help you move and keep your balance. Playing sports, running, stubbing your toe, and dropping something on your foot can damage your toes. Wearing shoes that are too loose or too tight can also cause toe problems.

Read the full article at MedlinePlus

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

Convert M20.42 to ICD-9-CMHistory

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

ICD-9-CM
735.4 Other hammer toe
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 M20.42Overview

Is M20.42 (Other hammer toe(s) (acquired)) a billable code?

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

What MS-DRG does M20.42 group to?

When other hammer toe(s) (acquired), left 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 M20.42?

Under the General Equivalence Mappings, other hammer toe(s) (acquired), left foot converts to ICD-9-CM 735.4 (other hammer toe). 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.