2026 ICD-10-CM Diagnosis Code S91.059AOpen bite, unspecified ankle, initial encounter

ICD-10-CM Codes›S00–T88›S90-S99›S91

ICD-10-CM S91.059A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

S91.059A is a billable ICD-10-CM diagnosis code for open bite, unspecified 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 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 604 through 605, 963 through 965. Coders also document this condition as animal bite of ankle. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Open wounds to limbs, initial encounter.

Code Identity

ICD-10-CM Code
S91.059A
Billable Status
Yes — Valid for Submission
Code Describes
Open bite, unspecified ankle, initial encounter
Short Description
Open bite, unspecified ankle, initial encounter
Same as the full description in the CMS dataset.
Parent Code
S91.059
Open bite, unspecified ankle

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS90-S99Injuries to the ankle and foot
CategoryS91Open wound of ankle, foot and toes
This CodeS91.059AOpen bite, unspecified ankle, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Animal bite of ankle
  • Dog bite of ankle
  • Human bite of ankle
  • Open bite of ankle

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Open wound of ankle, foot and toes (S91). 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 2026, published by CMS and the National Center for Health Statistics.

Clinical ClassificationClinical

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

CCSR INJ012
Open wounds to limbs, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Animal Bites

Wild animals usually avoid people. They might attack, however, if they feel threatened, are sick, or are protecting their young or territory. Attacks by pets are more common. Animal bites rarely are life-threatening, but if they become infected, you can develop serious medical problems.

Read the full article at MedlinePlus

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

Convert S91.059A to ICD-9-CMHistory

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

ICD-9-CM
891.0 Open wnd knee/leg/ankle
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 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About S91.059AOverview

Is S91.059A (Open bite, unspecified ankle) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report open bite, unspecified ankle, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in S91.059A mean?

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

What MS-DRG does S91.059A group to?

When open bite, unspecified ankle, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 604, 605, 963, 964, 965, with relative weights from 0.9160 to 2.7338 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of S91.059A?

Under the General Equivalence Mappings, open bite, unspecified ankle, initial encounter converts to ICD-9-CM 891.0 (open wnd knee/leg/ankle). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.