2027 ICD-10-CM Diagnosis Code S99.912AUnspecified injury of left ankle, initial encounter

ICD-10-CM Codes›S00–T88›S90-S99›S99

ICD-10-CM S99.912A
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

S99.912A is a billable ICD-10-CM diagnosis code for unspecified injury of left ankle, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 913 through 914, 963 through 965. Coders also document this condition as injury of left ankle. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other unspecified injury.

Code Identity

ICD-10-CM Code
S99.912A
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified injury of left ankle, initial encounter
Short Description
Unspecified injury of left ankle, initial encounter
Same as the full description in the CMS dataset.
Parent Code
S99.912
Unspecified injury of left ankle

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS90-S99Injuries to the ankle and foot
CategoryS99Other and unspecified injuries of ankle and foot
This CodeS99.912AUnspecified injury of left ankle, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Injury of left ankle

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Other and unspecified injuries of ankle and foot (S99). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to S99.912A: its own notes plus those printed at S99.9, block S90-S99, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Block S90-S99 Injuries to the ankle and foot applies to 3,324 codes
  • burns and corrosions (T20-T32)
  • fracture of ankle and malleolus (S82.-)
  • frostbite (T33-T34)
  • insect bite or sting, venomous (T63.4)
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • code to identify any retained foreign body, if applicable (Z18.-)

Notes

General instructions on how these codes are used.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

7th Character

Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.

From S99.9 Unspecified injury of ankle and foot applies to 18 codes
  • The appropriate 7th character is to be added to each code from subcategory S99.9
Values for category S99.9 Encounter: Initial, Subsequent, Sequela
  • Ainitial encounter this code
  • Dsubsequent encounter
  • Ssequela

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name S99.912A, its category, or a range that includes it.

Excludes2 1

These codes carry an Excludes2 note naming S99.912A: its condition is not part of those codes, and both may be reported when the patient has both.

  • S89 Other and unspecified injuries of lower leg
    other and unspecified injuries of ankle and foot (S99.-) names S99.-, which includes this code

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INJ027
Other unspecified injury
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Ankle Injuries and Disorders

Your ankle bone and the ends of your two lower leg bones make up the ankle joint. Your ligaments, which connect bones to one another, stabilize and support it. Your muscles and tendons move it.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert S99.912A to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
959.7 Lower leg injury NOS
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About S99.912AOverview

What is the ICD-10 code for unspecified injury of left ankle, initial encounter?

The ICD-10-CM code for unspecified injury of left ankle, initial encounter is S99.912A (sometimes written as S99912A). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is S99.912A (Unspecified injury of left ankle) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified injury of left ankle, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character A in S99.912A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for unspecified injury of left ankle, such as an emergency visit or first evaluation.

What MS-DRG does S99.912A group to?

When unspecified injury of left ankle, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 964, 965, 914, 913, 963, with relative weights from 0.9281 to 2.6361 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of S99.912A?

Under the General Equivalence Mappings, unspecified injury of left ankle, initial encounter converts to ICD-9-CM 959.7 (lower leg injury NOS). The mapping is approximate, so confirm the match fits the documentation.