2026 ICD-10-CM Diagnosis Code S56.999SOther injury of unspecified muscles, fascia and tendons at forearm level, unspecified arm, sequela
S56.999S is a billable ICD-10-CM diagnosis code for other injury of unspecified muscles, fascia and tendons at forearm level, unspecified arm, sequela. The 7th character S marks it as a sequela code, which reports a problem that remains after the original condition has resolved. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 913 through 914. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Injury, sequela.
Code Identity
Code Classification
Present on Admission (POA)Billing
S56.999S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Injury of muscle, fascia and tendon at forearm level (S56). 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
Arm Injuries and Disorders
Of the 206 bones in your body, three of them are in your arm: the humerus, radius, and ulna. Your arms are also made up of muscles, joints, tendons, and other connective tissue. Injuries to any of these parts of the arm can occur during sports, a fall, or an accident.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert S56.999S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About S56.999SOverview
Is S56.999S a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other injury of unspecified muscles, fascia and tendons at forearm level, unspecified arm, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in S56.999S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the other injury of unspecified muscles, fascia and tendons at forearm level, unspecified arm itself has resolved, not the original event.
What MS-DRG does S56.999S group to?
When other injury of unspecified muscles, fascia and tendons at forearm level, unspecified arm, sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 913, 914, with relative weights from 0.8855 to 1.6346 depending on complications. Higher weights mean higher Medicare reimbursement.
Is S56.999S exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for other injury of unspecified muscles, fascia and tendons at forearm level, unspecified arm, sequela on inpatient claims.
What is the ICD-9 equivalent of S56.999S?
Under the General Equivalence Mappings, other injury of unspecified muscles, fascia and tendons at forearm level, unspecified arm, sequela converts to ICD-9-CM 908.9 (late effect injury NOS). 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.
