2026 ICD-10-CM Diagnosis Code S81.009AUnspecified open wound, unspecified knee, initial encounter

ICD-10-CM S81.009A

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

S81.009A is a billable ICD-10-CM diagnosis code for unspecified open wound, 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Open wounds to limbs, initial encounter.

Code Identity

ICD-10-CM Code

S81.009A

Billable Status

Yes — Valid for Submission

Code Describes

Unspecified open wound, unspecified knee, initial encounter

Short Description

Unspecified open wound, unspecified knee, initial encounter

Same as the full description in the CMS dataset.

Parent Code

S81.009

Unspecified open wound, 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 CodeS81.009AUnspecified open wound, unspecified knee, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

Filter synonyms:

Comminuted fracture of patella
Fracture dislocation of patellofemoral joint
Fracture subluxation of knee joint
Fracture subluxation of patellofemoral joint
Glass in knee
Lateral patellofemoral dislocation
Open anterior dislocation of distal end of femur
Open anterior dislocation of proximal end of tibia
Open comminuted fracture of patella
Open dislocation of knee
Open dislocation of patella
Open division anterior cruciate ligament knee
Open division lateral collateral ligament knee
Open division ligament knee
Open division medial collateral ligament knee
Open division posterior cruciate ligament knee
Open fracture dislocation of knee joint
Open fracture dislocation of patellofemoral joint
Open fracture of bone of knee joint
Open fracture of patella
Open fracture patella, distal pole
Open fracture patella, proximal pole
Open fracture patella, transverse
Open fracture patella, vertical
Open fracture subluxation of knee joint
Open fracture subluxation of patellofemoral joint
Open lateral dislocation of proximal end of tibia
Open medial dislocation of proximal end of tibia
Open posterior dislocation of distal end of femur
Open posterior dislocation of proximal end of tibia
Open stellate fracture of patella
Open traumatic dislocation knee joint, anterior
Open traumatic dislocation knee joint, lateral
Open traumatic dislocation knee joint, medial
Open traumatic dislocation knee joint, posterior
Open traumatic dislocation knee joint, rotatory
Open traumatic dislocation of patellofemoral joint
Open traumatic dislocation patellofemoral joint, lateral
Open traumatic dislocation patellofemoral joint, medial
Open traumatic dislocation, head of fibula
Open traumatic subluxation knee joint
Open traumatic subluxation knee joint, anterior
Open traumatic subluxation knee joint, lateral
Open traumatic subluxation knee joint, medial
Open traumatic subluxation knee joint, posterior
Open traumatic subluxation knee joint, rotatory
Open traumatic subluxation patellofemoral joint
Open traumatic subluxation patellofemoral joint, lateral
Open traumatic subluxation patellofemoral joint, medial
Open traumatic subluxation, head of fibula
Open wound 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

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.

Read the full article at MedlinePlus

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

Convert S81.009A 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 S81.009AOverview

Is S81.009A (Unspecified open wound, unspecified knee) a billable code?

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

What does the 7th character A in S81.009A mean?

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

What MS-DRG does S81.009A group to?

When unspecified open wound, 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 S81.009A?

Under the General Equivalence Mappings, unspecified open wound, 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.

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.

Indicator	Meaning	CMS pays CC/MCC DRG
Y	Diagnosis was present at the time of inpatient admission	Yes
N	Diagnosis was not present at the time of admission	No
U	Documentation is insufficient to determine	No
W	Clinically undetermined	Yes
1	Unreported, exempt from POA reporting	No