M21 vs M40

M21 (Other acquired deformities of limbs) compared with M40 (Kyphosis and lordosis), from the official CMS tabular data. Both may be reported when both conditions are documented (Excludes2).

Can these codes be reported together?

Yes, when both are documented. M21 carries an Excludes2 note covering M40: “joints of the spine (M40-M54)”

Excludes2 marks distinct conditions — both may be reported when both are documented.

Side by side

	M21Other acquired deformities of limbs	M40Kyphosis and lordosis
Billing status	Non-billable header Report instead: M21.00, M21.021, M21.022, M21.029, M21.051	Non-billable header Report instead: M40.00, M40.03, M40.04, M40.05, M40.10
Classification	M00-M99 — Diseases of the Musculoskeletal System and Connective Tissue (M00-M99)	M00-M99 — Diseases of the Musculoskeletal System and Connective Tissue (M00-M99)
Definition	Other acquired deformities of limbs is a non-billable ICD-10-CM category code (M21).	Kyphosis and lordosis is a non-billable ICD-10-CM category code (M40).
Code first	—	underlying disease

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Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources