S56.399Header code — not billable

Other injury of extensor or abductor muscles, fascia and tendons of unspecified thumb at forearm level

Short description: Inj extn/abdr musc/fasc/tend of thmb at forearm level

Chapter
19. Injury, poisoning and certain other consequences of external causes
Category
S56
Effective date
October 1, 2026

Related codes in category S56

S56Injury of muscle, fascia and tendon at forearm levelS56.0Injury of flexor musc/fasc/tend thumb at forearm levelS56.00Unsp injury of flexor musc/fasc/tend thumb at forearm levelS56.001Unsp injury of flexor musc/fasc/tend r thm at forarm lvS56.001AUnsp inj flexor musc/fasc/tend r thm at forarm lv, initYesS56.001DUnsp inj flexor musc/fasc/tend r thm at forarm lv, subsYesS56.001SUnsp inj flexor musc/fasc/tend r thm at forarm lv, sequelaYesS56.002Unsp injury of flexor musc/fasc/tend left thumb at forarm lvS56.002AUnsp inj flexor musc/fasc/tend l thm at forarm lv, initYesS56.002DUnsp inj flexor musc/fasc/tend l thm at forarm lv, subsYesS56.002SUnsp inj flexor musc/fasc/tend l thm at forarm lv, sequelaYesS56.009Unsp injury of flexor musc/fasc/tend thmb at forearm level

Frequently asked questions

What is ICD-10 code S56.399?

S56.399 is an ICD-10-CM diagnosis code for Other injury of extensor or abductor muscles, fascia and tendons of unspecified thumb at forearm level.

Is S56.399 a billable code?

No. S56.399 is a category/header code, not billable on its own — use one of its more specific child codes instead.

What ICD-10-CM chapter is S56.399 in?

S56.399 falls under Chapter 19: Injury, poisoning and certain other consequences of external causes.

When did S56.399 become effective?

S56.399 has been effective since October 1, 2026, per the CMS/CDC ICD-10-CM annual release.

What other codes are related to S56.399?

S56.399 belongs to category S56, which includes 12 other codes — see the related codes list on this page.

ICD-10-CM data maintained by CDC/CMS (public domain). Always verify codes with authoritative sources before making coding or billing decisions.