2026 ICD-10-CM Diagnosis Code M21.6X9Other acquired deformities of unspecified foot

ICD-10-CM Codes›M00–M99›M20-M25›M21

ICD-10-CM M21.6X9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M21.6X9 is a billable ICD-10-CM diagnosis code for other acquired deformities of unspecified 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
M21.6X9
Billable Status
Yes — Valid for Submission
Code Describes
Other acquired deformities of unspecified foot
Short Description
Other acquired deformities of unspecified foot
Same as the full description in the CMS dataset.
Parent Code
M21.6X
Other acquired deformities of foot

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM21Other acquired deformities of limbs
This CodeM21.6X9Other acquired deformities of unspecified foot

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Abduction deformity of foot
  • Absent bone in foot
  • Acquired abduction deformity of foot
  • Acquired adduction deformity of foot
  • Acquired cavovarus deformity of foot
  • Acquired cavus deformity of foot
  • Acquired dorsiflexed first ray
  • Acquired dorsiflexed forefoot
  • Acquired dorsiflexion deformity of foot
  • Acquired equinus deformity of foot
  • Acquired forefoot abductus
  • Acquired forefoot adductus
  • Acquired metatarsus adductus
  • Acquired plantar-flexed fifth ray
  • Acquired plantar-flexed first ray
  • Acquired plantar-flexed forefoot
  • Adductus deformity of foot
  • Angulation of bone in foot
  • Bowing of foot bone
  • Calcaneovalgus deformity of foot
  • Cavovarus deformity of foot
  • Correction of low arch on tiptoe
  • Defect of articular cartilage
  • Deformity of bone in foot
  • Deformity of metatarsal
  • Dorsiflexion deformity of foot
  • Finding of movement of foot
  • Forefoot adductus
  • Loss of protective sensation of skin
  • Osteochondral defect of talus
  • Peripheral vascular disease of foot with loss of protective sensation and deformity
  • Plantar flexion deformity of midtarsal joint
  • Plantarflexion deformity of foot
  • Postural calcaneovalgus
  • Pronated forefoot
  • Pronation deformity of the foot
  • Pronation of foot
  • Shortening of bone in foot
  • Supination deformity of foot
  • Supination deformity of forefoot
  • Talar tilt
  • Toeing-out

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

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 M21.6X9 to ICD-9-CMHistory

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

ICD-9-CM
736.79 Acq ankle-foot def 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 M21.6X9Overview

Is M21.6X9 (Other acquired deformities of foot) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other acquired deformities of unspecified foot on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M21.6X9 group to?

When other acquired deformities of unspecified 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 M21.6X9?

Under the General Equivalence Mappings, other acquired deformities of unspecified foot converts to ICD-9-CM 736.79 (acq ankle-foot def NEC). 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.