2026 ICD-10-CM Diagnosis Code S23.420ASprain of sternoclavicular (joint) (ligament), initial encounter
S23.420A is a billable ICD-10-CM diagnosis code for sprain of sternoclavicular (joint) (ligament), 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 205 through 206, 963 through 965. Coders also document this condition as sprain of sternum. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Sprains and strains, initial encounter.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Sprain of sternum
- Sternoclavicular sprain
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Dislocation and sprain of joints and ligaments of thorax (S23). 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
Chest Injuries and Disorders
The chest is the part of your body between your neck and your abdomen (belly). The medical term for your chest is thorax.
The full article covers:
- What is the chest?
- What are chest injuries and disorders?
- How are chest injuries and disorders diagnosed?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert S23.420A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About S23.420AOverview
Is S23.420A (Sprain of sternoclavicular (joint) (ligament)) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report sprain of sternoclavicular (joint) (ligament), initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in S23.420A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for sprain of sternoclavicular (joint) (ligament), such as an emergency visit or first evaluation.
What MS-DRG does S23.420A group to?
When sprain of sternoclavicular (joint) (ligament), initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 205, 206, 963, 964, 965, with relative weights from 0.9405 to 2.7338 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of S23.420A?
Under the General Equivalence Mappings, sprain of sternoclavicular (joint) (ligament), initial encounter converts to ICD-9-CM 848.41 (sprain sternoclavicular). 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.
