M21.4 vs Q66.5
M21.4 (Flat foot pes planus) compared with Q66.5 (Congenital pes planus), from the official CMS tabular data. Do not report these codes together: the official tabular list marks them Excludes1.
Can these codes be reported together?
No — do not report together. M21.4 carries an Excludes1 note covering Q66.5: “congenital pes planus (Q66.5-)”
Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).
No — do not report together. M21.4 carries an Excludes1 note covering Q66.5: “congenital deformities and malformations of limbs (Q65-Q66, Q68-Q74)”
Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).
No — do not report together. Q66.5 carries an Excludes1 note covering M21.4: “pes planus, acquired (M21.4)”
Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).
Side by side
| M21.4Flat foot pes planus | Q66.5Congenital pes planus | |
|---|---|---|
| Billing status | Non-billable header | Non-billable header |
| Classification | M00-M99 — Diseases of the Musculoskeletal System and Connective Tissue (M00-M99) | Q00-Q99 — Congenital Malformations, Deformations and Chromosomal Abnormalities (Q00-Q99) |
| Definition | Flat foot pes planus is a non-billable ICD-10-CM category code (M21.4). | Congenital pes planus is a non-billable ICD-10-CM category code (Q66.5). |
| Includes | — | Congenital flat foot Congenital rigid flat foot Congenital spastic (everted) flat foot |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources