Acquired deformities of fingers and toes (M20) ICD-10-CM
The M20 code range covers acquired deformities of fingers and toes with 47 ICD-10-CM diagnosis codes. 33 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Codes in the M20 Range 47 codes · 33 billable
- M20 Acquired deformities of fingers and toesNon-billable
- M20.0 Deformity of finger(s)Non-billable
- M20.00 Unspecified deformity of finger(s)Non-billable
- M20.001 Unspecified deformity of right finger(s)
- M20.002 Unspecified deformity of left finger(s)
- M20.009 Unspecified deformity of unspecified finger(s)
- M20.01 Mallet fingerNon-billable
- M20.011 Mallet finger of right finger(s)
- M20.012 Mallet finger of left finger(s)
- M20.019 Mallet finger of unspecified finger(s)
- M20.02 Boutonniere deformityNon-billable
- M20.021 Boutonniere deformity of right finger(s)
- M20.022 Boutonniere deformity of left finger(s)
- M20.029 Boutonniere deformity of unspecified finger(s)
- M20.03 Swan-neck deformityNon-billable
- M20.031 Swan-neck deformity of right finger(s)
- M20.032 Swan-neck deformity of left finger(s)
- M20.039 Swan-neck deformity of unspecified finger(s)
- M20.09 Other deformity of finger(s)Non-billable
- M20.091 Other deformity of right finger(s)
- M20.092 Other deformity of left finger(s)
- M20.099 Other deformity of finger(s), unspecified finger(s)
- M20.1 Hallux valgus (acquired)Non-billable
- M20.10 Hallux valgus (acquired), unspecified foot
- M20.11 Hallux valgus (acquired), right foot
- M20.12 Hallux valgus (acquired), left foot
- M20.2 Hallux rigidusNon-billable
- M20.20 Hallux rigidus, unspecified foot
- M20.21 Hallux rigidus, right foot
- M20.22 Hallux rigidus, left foot
- M20.3 Hallux varus (acquired)Non-billable
- M20.30 Hallux varus (acquired), unspecified foot
- M20.31 Hallux varus (acquired), right foot
- M20.32 Hallux varus (acquired), left foot
- M20.4 Other hammer toe(s) (acquired)Non-billable
- M20.40 Other hammer toe(s) (acquired), unspecified foot
- M20.41 Other hammer toe(s) (acquired), right foot
- M20.42 Other hammer toe(s) (acquired), left foot
- M20.5 Other deformities of toe(s) (acquired)Non-billable
- M20.5X Other deformities of toe(s) (acquired)Non-billable
- M20.5X1 Other deformities of toe(s) (acquired), right foot
- M20.5X2 Other deformities of toe(s) (acquired), left foot
- M20.5X9 Other deformities of toe(s) (acquired), unspecified foot
- M20.6 Acquired deformities of toe(s), unspecifiedNon-billable
- M20.60 Acquired deformities of toe(s), unspecified, unspecified foot
- M20.61 Acquired deformities of toe(s), unspecified, right foot
- M20.62 Acquired deformities of toe(s), unspecified, left foot
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the M20 range.
Bunion
Abnormal swelling of the inner aspect of the first metatarsal head affecting the first METATARSOPHALANGEAL JOINT.
Bunion, Tailor's
Abnormal swelling of the outer aspect of the fifth metatarsal head affecting the fifth METATARSOPHALANGEAL JOINT.
Hallux Rigidus
A condition caused by degenerative arthritis (see OSTEOARTHRITIS) of the METATARSOPHALANGEAL JOINT of the great toe and characterized by pain and limited dorsiflexion, but relatively unrestricted plantar flexion.
Hallux Valgus
Lateral displacement of the great toe (HALLUX), producing deformity of the first METATARSOPHALANGEAL JOINT with callous, bursa, or BUNION formation over the bony prominence.
Hallux Varus
Displacement of the great toe (HALLUX) towards the midline or away from the other TOES. It can be congenital or acquired.
Metatarsophalangeal Joint
The articulation between a metatarsal bone (METATARSAL BONES) and a phalanx.
About the M20 Code Range
The M20 ICD-10 codes cover various acquired deformities of fingers and toes, including specific conditions affecting individual fingers or toes on either hand or foot. These codes are used to document deformities such as mallet finger, boutonniere deformity, swan-neck deformity, hallux valgus, and hammer toes arising after birth or injury.
This section provides precise diagnosis codes for conditions like mallet finger (codes M20.01x, related to tendon ruptures causing fingertip drooping), boutonniere deformity (M20.02x, characterized by finger joint contracture), and swan-neck deformity (M20.03x, involving hyperextension of the finger joints). Coders can differentiate these based on laterality and finger or toe affected. For example, M20.11 corresponds to acquired hallux valgus (bunions) of the right foot, with synonyms including “bunion” or “Hallux valgus due to metatarsus primus varus.” Similarly, M20.5X covers other acquired toe deformities like mallet toe and overriding toes. Using these detailed ICD-10 codes ensures specificity when coding acquired finger and toe deformities documented in clinical settings.
Questions About This Page
How many billable codes are in the M20 range?
Of the 47 codes in this range, 33 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the M20 range classify?
The range classifies acquired deformities of fingers and toes. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
