2026 ICD-10-CM Diagnosis Code S91.309AUnspecified open wound, unspecified foot, initial encounter

ICD-10-CM S91.309A

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

S91.309A is a billable ICD-10-CM diagnosis code for unspecified open wound, unspecified foot, 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

S91.309A

Billable Status

Yes — Valid for Submission

Code Describes

Unspecified open wound, unspecified foot, initial encounter

Short Description

Unspecified open wound, unspecified foot, initial encounter

Same as the full description in the CMS dataset.

Parent Code

S91.309

Unspecified open wound, unspecified foot

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 CodeS91.309AUnspecified open wound, unspecified foot, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

Filter synonyms:

Foreign body in heel
Fracture of base of fifth metatarsal
Fracture of cuboid
Fracture of intermediate cuneiform
Fracture of lateral cuneiform
Fracture of medial cuneiform
Fracture of multiple metatarsal bones
Fracture of multiple tarsal bones
Fracture of navicular
Glass in dorsum of foot
Glass in foot
Glass in heel
Glass in sole of foot
Injury of deep plantar artery
Injury of digital vein of foot
Injury of dorsalis pedis artery
Multiple fractures of foot
Multiple open wounds of digital vessel of foot
Multiple open wounds of foot
Multiple open wounds of lower limb
Nail wound of dorsum of foot
Nail wound of foot
Open comminuted fracture of metatarsal bone
Open division foot ligament
Open division ligament ankle and/or foot
Open division of midtarsal joint ligament
Open division tarsometatarsal ligament
Open fracture dislocation of foot
Open fracture dislocation of midtarsal joint
Open fracture dislocation of subtalar joint
Open fracture dislocation of tarsometatarsal joint
Open fracture metatarsal base
Open fracture metatarsal head
Open fracture metatarsal neck
Open fracture metatarsal shaft
Open fracture of base of fifth metatarsal
Open fracture of cuboid bone of foot
Open fracture of cuneiform bone of foot
Open fracture of fifth metatarsal bone
Open fracture of first metatarsal bone
Open fracture of foot
Open fracture of fourth metatarsal bone
Open fracture of intermediate cuneiform bone of foot
Open fracture of lateral cuneiform bone of foot
Open fracture of medial cuneiform bone of foot
Open fracture of metaphysis of fifth metatarsal bone
Open fracture of metaphysis of first metatarsal bone
Open fracture of metaphysis of fourth metatarsal bone
Open fracture of metaphysis of metatarsal bone
Open fracture of metaphysis of second metatarsal bone
Open fracture of metaphysis of third metatarsal bone
Open fracture of multiple metatarsal bones
Open fracture of multiple tarsal bones
Open fracture of navicular bone of foot
Open fracture of second metatarsal bone
Open fracture of tarsal AND metatarsal bones
Open fracture of tarsal bone
Open fracture of third metatarsal bone
Open fracture subluxation of foot
Open fracture subluxation of midtarsal joint
Open fracture subluxation of subtalar joint
Open fracture subluxation of tarsometatarsal joint
Open injury of digital vein of foot
Open injury, deep plantar artery
Open injury, dorsalis pedis artery
Open lateral dislocation of subtalar joint
Open medial dislocation of subtalar joint
Open traumatic dislocation of tarsometatarsal joint
Open traumatic dislocation, midtarsal joint
Open traumatic dislocation, pantalar
Open traumatic dislocation, subtalar joint
Open traumatic subluxation of tarsometatarsal joint
Open traumatic subluxation, foot
Open traumatic subluxation, midtarsal joint
Open traumatic subluxation, pantalar
Open traumatic subluxation, subtalar joint
Open wound foot, dorsum
Open wound foot, plantar
Open wound of foot
Open wound of foot, excluding toe
Open wound, heel
Subluxation of tarsometatarsal joint
Traumatic arthropathy of talonavicular joint
Traumatic dislocation of tarsometatarsal joint

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

Foot Injuries and Disorders

Each of your feet has 26 bones, 33 joints, and more than 100 tendons, muscles, and ligaments. No wonder a lot of things can go wrong. Here are a few common problems:

Read the full article at MedlinePlus

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

Convert S91.309A to ICD-9-CMHistory

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

ICD-9-CM

892.0 Open wound of foot

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 S91.309AOverview

Is S91.309A (Unspecified open wound, unspecified foot) a billable code?

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

What does the 7th character A in S91.309A mean?

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

What MS-DRG does S91.309A group to?

When unspecified open wound, unspecified foot, 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 S91.309A?

Under the General Equivalence Mappings, unspecified open wound, unspecified foot, initial encounter converts to ICD-9-CM 892.0 (open wound of foot). 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