M21.40 – Flat foot [pes planus] (acquired), unspecified foot

ICD-10-CM 2027 diagnosis code · Other joint disorders

Billable code

ICD-10-CM code M21.40

Code: M21.40 (claims format: M2140)
Description: Flat foot [pes planus] (acquired), unspecified foot
Billable: Yes – valid for HIPAA-covered transactions
Valid for: Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter: 13. Diseases of the musculoskeletal system and connective tissue (M00-M99)
Block: M20-M25 Other joint disorders
Parent codes: M21 › M21.4

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

M21 – Other acquired deformities of limbs

Excludes1 (not coded here):

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):

acquired deformities of fingers or toes (M20.-)
coxa plana (M91.2)

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

Excludes1 (not coded here):

congenital pes planus (Q66.5-)

Block M20-M25

Excludes2 (not included here):

joints of the spine (M40-M54)

Related codes in M21.4

Frequently asked questions

What is ICD-10 code M21.40?

M21.40 is the ICD-10-CM code for flat foot [pes planus] (acquired), unspecified foot, in the block M20-M25 (Other joint disorders).

Is M21.40 a billable code?

Yes. M21.40 is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.

What category does M21.40 belong to?

It belongs to category M21 – Other acquired deformities of limbs.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.