2026 ICD-10-CM Diagnosis Code M21Other acquired deformities of limbs

ICD-10-CM Codes›M00–M99›M20-M25›M21

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

M21 is a non-billable ICD-10-CM category code for other acquired deformities of limbs, so it cannot be submitted on claims. Use a more specific code from this category instead, such as M21.00, M21.021, M21.022, and M21.029.

Code Identity

ICD-10-CM Code
M21
Billable Status
No — Non-Billable Category
Code Describes
Other acquired deformities of limbs
Chapter
M20-M25
Other joint disorders

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM21Other acquired deformities of limbs
This CodeM21Other acquired deformities of limbs

Specific Coding for Other acquired deformities of limbsOverview

Non-specific codes like M21 require more characters. Use one of these billable codes instead:

  • M21.0 for Valgus deformity, not elsewhere classified

  • Use M21.00 for Valgus deformity, not elsewhere classified, unspecified site

  • M21.02 for Valgus deformity, not elsewhere classified, elbow

  • M21.05 for Valgus deformity, not elsewhere classified, hip

  • M21.06 for Valgus deformity, not elsewhere classified, knee

  • M21.07 for Valgus deformity, not elsewhere classified, ankle

  • M21.1 for Varus deformity, not elsewhere classified

  • Use M21.10 for Varus deformity, not elsewhere classified, unspecified site

  • M21.12 for Varus deformity, not elsewhere classified, elbow

  • M21.15 for Varus deformity, not elsewhere classified, hip

  • M21.16 for Varus deformity, not elsewhere classified, knee

  • M21.17 for Varus deformity, not elsewhere classified, ankle

  • M21.2 for Flexion deformity

  • Use M21.20 for Flexion deformity, unspecified site

  • M21.21 for Flexion deformity, shoulder

  • M21.22 for Flexion deformity, elbow

  • M21.23 for Flexion deformity, wrist

  • M21.24 for Flexion deformity, finger joints

  • M21.25 for Flexion deformity, hip

  • M21.26 for Flexion deformity, knee

  • M21.27 for Flexion deformity, ankle and toes

  • M21.3 for Wrist or foot drop (acquired)

  • M21.33 for Wrist drop (acquired)

  • M21.37 for Foot drop (acquired)

  • M21.4 for Flat foot [pes planus] (acquired)

  • Use M21.40 for Flat foot [pes planus] (acquired), unspecified foot

  • Use M21.41 for Flat foot [pes planus] (acquired), right foot

  • Use M21.42 for Flat foot [pes planus] (acquired), left foot

  • M21.5 for Acquired clawhand, clubhand, clawfoot and clubfoot

  • M21.51 for Acquired clawhand

  • M21.52 for Acquired clubhand

  • M21.53 for Acquired clawfoot

  • M21.54 for Acquired clubfoot

  • M21.6 for Other acquired deformities of foot

  • M21.61 for Bunion

  • M21.62 for Bunionette

  • M21.6X for Other acquired deformities of foot

  • M21.7 for Unequal limb length (acquired)

  • Use M21.70 for Unequal limb length (acquired), unspecified site

  • M21.72 for Unequal limb length (acquired), humerus

  • M21.73 for Unequal limb length (acquired), ulna and radius

  • M21.75 for Unequal limb length (acquired), femur

  • M21.76 for Unequal limb length (acquired), tibia and fibula

  • M21.8 for Other specified acquired deformities of limbs

  • Use M21.80 for Other specified acquired deformities of unspecified limb

  • M21.82 for Other specified acquired deformities of upper arm

  • M21.83 for Other specified acquired deformities of forearm

  • M21.85 for Other specified acquired deformities of thigh

  • M21.86 for Other specified acquired deformities of lower leg

  • M21.9 for Unspecified acquired deformity of limb and hand

  • Use M21.90 for Unspecified acquired deformity of unspecified limb

  • M21.92 for Unspecified acquired deformity of upper arm

  • M21.93 for Unspecified acquired deformity of forearm

  • M21.94 for Unspecified acquired deformity of hand

  • M21.95 for Unspecified acquired deformity of thigh

  • M21.96 for Unspecified acquired deformity of lower leg

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Type 1 Excludes

  • acquired absence of limb Z89
  • congenital absence of limbs Q71 Q73
  • congenital deformities and malformations of limbs Q65 Q66 Q68 Q74

Type 2 Excludes

  • acquired deformities of fingers or toes M20
  • coxa plana M91.2

Patient EducationClinical

Joint Disorders

Your joints are places where two or more bones come together. Your shoulders, elbows, hips, knees, and knuckles are all joints. Your spine has joints, too.

The full article covers:

  • What are joints?
  • What are joint disorders?
  • What diseases can affect the joints?
  • What types of joint disorders happen from sudden injuries?
  • What types of joint disorders happen from overuse?
  • How can I keep my joints healthy?

Read the full article at MedlinePlus

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

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 M21Overview

Is M21 (Other acquired deformities of limbs) a billable code?

No. This is a category header that groups the codes for other acquired deformities of limbs, and headers cannot be submitted on claims. Claims for other acquired deformities of limbs need a more specific code from this category, such as M21.00, M21.021, and M21.022.