2026 ICD-10-CM Diagnosis Code S40.021AContusion of right upper arm, initial encounter
S40.021A is a billable ICD-10-CM diagnosis code for contusion of right upper arm, 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 contusion of axillary region. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Superficial injury; contusion, initial encounter.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Contusion of axillary region
- Contusion of right axillary region
- Contusion of right shoulder
- Contusion of right upper arm
- Contusion of upper arm
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Superficial injury of shoulder and upper arm (S40). 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
Bruises
A bruise is a mark on your skin caused by blood trapped under the surface. It happens when an injury crushes small blood vessels but does not break the skin. Those vessels break open and leak blood under the skin.
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Convert S40.021A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About S40.021AOverview
Is S40.021A (Contusion of right upper arm) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report contusion of right upper arm, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in S40.021A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for contusion of right upper arm, such as an emergency visit or first evaluation.
What MS-DRG does S40.021A group to?
When contusion of right upper arm, 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 S40.021A?
Under the General Equivalence Mappings, contusion of right upper arm, initial encounter converts to ICD-9-CM 923.03 (contusion of upper arm). 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.
