2026 ICD-10-CM Diagnosis Code M84.375KStress fracture, left foot, subsequent encounter for fracture with nonunion

ICD-10-CM Codes›M00–M99›M80-M85›M84

ICD-10-CM M84.375K
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M84.375K is a billable ICD-10-CM diagnosis code for stress fracture, left foot, subsequent encounter for fracture with nonunion. The 7th character K reports a subsequent encounter for a fracture that has failed to heal, called a nonunion. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 564 through 566. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Stress fracture, subsequent encounter.

Code Identity

ICD-10-CM Code
M84.375K
Billable Status
Yes — Valid for Submission
Code Describes
Stress fracture, left foot, subsequent encounter for fracture with nonunion
Short Description
Stress fracture, left foot, subs for fx w nonunion
Parent Code
M84.375
Stress fracture, left foot

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM80-M85Disorders of bone density and structure
CategoryM84Disorder of continuity of bone
This CodeM84.375KStress fracture, left foot, subsequent encounter for fracture with nonunion

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Fracture of left calcaneum
  • Fracture of navicular
  • Stress fracture of calcaneus
  • Stress fracture of left calcaneus
  • Stress fracture of left foot
  • Stress fracture of left tarsus
  • Stress fracture of metatarsal bone
  • Stress fracture of metatarsal bone of left foot
  • Stress fracture of navicular bone of foot
  • Stress fracture of navicular bone of left foot
  • Stress fracture of tarsal bone

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MUS017
Stress fracture, subsequent 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 M84.375K to ICD-9-CMHistory

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

ICD-9-CM
733.82 Nonunion of fracture
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 M84.375KOverview

Is M84.375K (Stress fracture, left foot) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report stress fracture, left foot, subsequent encounter for fracture with nonunion on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character K in M84.375K mean?

The final character K reports a subsequent encounter where the stress fracture, left foot has failed to heal, called a nonunion.

What MS-DRG does M84.375K group to?

When stress fracture, left foot, subsequent encounter for fracture with nonunion is the principal diagnosis on an inpatient stay, it groups to MS-DRG 564, 565, 566, with relative weights from 0.7493 to 1.5436 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M84.375K?

Under the General Equivalence Mappings, stress fracture, left foot, subsequent encounter for fracture with nonunion converts to ICD-9-CM 733.82 (nonunion of fracture). 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.