2026 ICD-10-CM Diagnosis Code S81.002AUnspecified open wound, left knee, initial encounter
S81.002A is a billable ICD-10-CM diagnosis code for unspecified open wound, left 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 disorder of left patella. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Open wounds to limbs, initial encounter.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Disorder of left patella
- Fracture of left patella
- Open dislocation of patella
- Open fracture of left patella
- Open fracture of patella
- Open traumatic dislocation of left knee joint
- Open traumatic dislocation of left patella
- Open wound of left 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.
Patient EducationClinical
Knee Injuries and Disorders
Your knee joint is made up of bone, cartilage, ligaments and fluid. Muscles and tendons help the knee joint move. When any of these structures is hurt or diseased, you have knee problems. Knee problems can cause pain and difficulty walking.
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Convert S81.002A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About S81.002AOverview
Is S81.002A (Unspecified open wound, left knee) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report unspecified open wound, left knee, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in S81.002A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for unspecified open wound, left knee, such as an emergency visit or first evaluation.
What MS-DRG does S81.002A group to?
When unspecified open wound, left 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 S81.002A?
Under the General Equivalence Mappings, unspecified open wound, left 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.
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.
