2026 ICD-10-CM Diagnosis Code S81.059AOpen bite, unspecified knee, initial encounter

ICD-10-CM Codes›S00–T88›S80-S89›S81

ICD-10-CM S81.059A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

S81.059A is a billable ICD-10-CM diagnosis code for open bite, unspecified knee, 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 knee. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Open wounds to limbs, initial encounter.

Code Identity

ICD-10-CM Code
S81.059A
Billable Status
Yes — Valid for Submission
Code Describes
Open bite, unspecified knee, initial encounter
Short Description
Open bite, unspecified knee, initial encounter
Same as the full description in the CMS dataset.
Parent Code
S81.059
Open bite, unspecified knee

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionS80-S89Injuries to the knee and lower leg
CategoryS81Open wound of knee and lower leg
This CodeS81.059AOpen bite, unspecified knee, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Animal bite of knee
  • Bite wound of knee region
  • Dog bite of knee
  • Human bite of knee

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Open wound of knee and lower leg (S81). 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 S81.059A 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 S81.059AOverview

What is the ICD-10 code for open bite, unspecified knee, initial encounter?

The ICD-10-CM code for open bite, unspecified knee, initial encounter is S81.059A (sometimes written as S81059A). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is S81.059A (Open bite, unspecified knee) a billable code?

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

What does the 7th character A in S81.059A mean?

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

What MS-DRG does S81.059A group to?

When open bite, unspecified knee, 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 S81.059A?

Under the General Equivalence Mappings, open bite, unspecified knee, 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.