M20.11 identifies an acquired lateral deviation of the great toe at the first metatarsophalangeal joint, confirmed on the right foot, resulting from structural changes rather than a congenital condition.
Verified May 8, 2026 · 5 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 11
- Region
- Foot & ankle
Documentation tips
What should appear in the chart to support M20.11.
Source · Editorial brief grounded in 5 cited references ↓
- Document laterality explicitly as 'right foot' — M20.11 is not valid without confirmed right-side involvement.
- Record weight-bearing radiograph findings, including hallux valgus angle (HVA) and intermetatarsal angle (IMA), to support medical necessity for surgical intervention.
- Specify 'acquired' versus congenital origin; a pediatric or congenital deformity should be evaluated under Q66.2– rather than M20.11.
- If bursitis or metatarsalgia is separately documented, add M76.62 or M77.51 as additional diagnoses — do not fold them into M20.11.
- For surgical cases, document failed conservative management (orthotics, padding, shoe modification) to support pre-authorization and audit defense.
Related CPT procedures
Procedure codes commonly billed with M20.11. Linking the right diagnosis to the right procedure is what establishes medical necessity.
Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis
Common coding pitfalls
The recurring mistakes coders make with M20.11 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Reporting M20.11 and M21.611 together for the same foot — these codes carry an Excludes1 relationship and cannot be billed simultaneously for the same encounter.
- Using M20.11 for a congenital great-toe deformity; acquired and congenital conditions map to distinct code families (M20.1– vs. Q66.2–).
- Omitting laterality and defaulting to an unspecified code when the operative or clinical note clearly documents the right foot — this triggers specificity downcoding and potential payer rejection.
- Applying M20.11 when the documentation only describes a bony bump with no angular deformity measurement — that presentation maps to M21.611, not M20.11.
Clinical context
Source · Editorial summary grounded in 5 cited references ↓
M20.11 applies when a patient presents with a documented acquired hallux valgus deformity of the right foot — typically confirmed by weight-bearing radiographs showing a hallux valgus angle (HVA) greater than 15° and, for surgical cases, an intermetatarsal angle (IMA) of 12° or more. The 'acquired' qualifier rules out congenital conditions; if deformity is congenital or present since birth, evaluate Q66.2– instead.
M20.11 and M21.611 (Bunion of right foot) are frequently confused but are mutually exclusive via Excludes1 notes. Use M20.11 when the angular structural deformity is the primary finding — especially in surgical workups. Use M21.611 when documentation describes a medial bony prominence at the first MTP joint without significant angular deformity. Do not report both for the same encounter.
For bilateral hallux valgus, report M20.11 (right) and M20.12 (left) together — there is no single bilateral code in this family. Ancillary codes such as M77.51 (metatarsalgia) or M76.62 (bursitis of foot) may be added when separately documented and clinically supported.
Sibling codes
Other billable codes under M20.1 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 5 cited references ↓
01What is the difference between M20.11 and M21.611?
02Can I use M20.11 for bilateral hallux valgus?
03What radiographic findings support M20.11?
04Is M20.11 appropriate for a congenital toe deformity?
05Which CPT codes are typically paired with M20.11 for bunionectomy?
06Can M20.11 be reported with metatarsalgia or bursitis codes?
07Does M20.11 require a 7th-character extension?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026 (FY2026, effective Oct 1, 2025)
- 02aapc.comhttps://www.aapc.com/codes/icd-10-codes/M20.11
- 03icdcodes.aihttps://icdcodes.ai/diagnosis/hallux-valgus/documentation
- 04icdcodes.aihttps://icdcodes.ai/diagnosis/bunion-right-foot/documentation
- 05associationdatabase.comhttps://associationdatabase.com/aws/NYSPMA/page_template/show_detail/186387?model_name=news_article
Mira AI Scribe
Mira's AI scribe captures the affected side (right), radiographic angle measurements (HVA, IMA) from weight-bearing X-ray findings, severity of deformity, and any prior conservative treatment documented in the visit note. This prevents a specificity downgrade to an unspecified code, shields against M21.611 substitution errors, and provides the audit trail needed for surgical pre-authorization.
See how Mira captures M20.11 documentation