2027 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 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

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
Short Description
Other acquired deformities of limbs
Same as the full description in the CMS dataset.
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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to M21: its own notes plus those printed at block M00-M25, block M20-M25, and Chapter 13. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Block M00-M25 applies to 2,249 codes
  • Disorders affecting predominantly peripheral (limb) joints

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

  • acquired absence of limb (Z89.-)
  • congenital absence of limbs (Q71-Q73)
  • congenital deformities and malformations of limbs (Q65-Q66, Q68-Q74)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

On M21 itself
  • acquired deformities of fingers or toes (M20.-)
  • coxa plana (M91.2)
From Block M20-M25 Other joint disorders applies to 719 codes
From Chapter 13 (M00-M99) Diseases of the musculoskeletal system and connective tissue applies to 6,687 codes
  • arthropathic psoriasis (L40.5-)
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • compartment syndrome (traumatic) (T79.A-)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Notes

General instructions on how these codes are used.

From Chapter 13 (M00-M99) Diseases of the musculoskeletal system and connective tissue applies to 6,687 codes
  • Use an external cause code following the code for the musculoskeletal condition, if applicable, to identify the cause of the musculoskeletal condition

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name M21, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming M21: they are not reported together with it, unless the two conditions are unrelated.

  • M23 Internal derangement of knee
    deformity of knee (M21.-)

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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About M21Overview

What is the ICD-10 code for other acquired deformities of limbs?

M21 is the ICD-10-CM category for other acquired deformities of limbs, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

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.

Can M21 be reported with a code from Z89?

Not as a rule. The Excludes1 note on M21 lists "acquired absence of limb (Z89.-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).