2026 ICD-10-CM Diagnosis Code S91.001AUnspecified open wound, right ankle, initial encounter

ICD-10-CM Codes›S00–T88›S90-S99›S91

ICD-10-CM S91.001A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

S91.001A is a billable ICD-10-CM diagnosis code for unspecified open wound, right 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Open wounds to limbs, initial encounter.

Code Identity

ICD-10-CM Code
S91.001A
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified open wound, right ankle, initial encounter
Short Description
Unspecified open wound, right ankle, initial encounter
Same as the full description in the CMS dataset.
Parent Code
S91.001
Unspecified open wound, right 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 CodeS91.001AUnspecified open wound, right ankle, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Bimalleolar fracture of right ankle
  • Dislocation of joint of right ankle
  • Fracture of right lateral malleolus
  • Fracture of right medial malleolus
  • Open bimalleolar fracture
  • Open bimalleolar fracture of right ankle
  • Open dislocation of ankle
  • Open fracture of distal end of right fibula
  • Open fracture of distal end of right tibia
  • Open fracture of distal tibia and distal fibula
  • Open fracture of medial malleolus
  • Open fracture of medial malleolus of right tibia
  • Open fracture of right ankle
  • Open fracture of right fibula
  • Open fracture of right lateral malleolus of fibula
  • Open fracture of right tibia
  • Open fracture of tibia AND fibula
  • Open traumatic dislocation of joint of right ankle
  • Open trimalleolar fracture
  • Open trimalleolar fracture of right ankle
  • Open wound of right ankle
  • Trimalleolar fracture of right 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

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 S91.001A 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 S91.001AOverview

Is S91.001A (Unspecified open wound, right ankle) a billable code?

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

What does the 7th character A in S91.001A mean?

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

What MS-DRG does S91.001A group to?

When unspecified open wound, right 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 S91.001A?

Under the General Equivalence Mappings, unspecified open wound, right 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.