2026 ICD-10-CM Diagnosis Code M40.30Flatback syndrome, site unspecified

ICD-10-CM Codes›M00–M99›M40-M43›M40

ICD-10-CM M40.30
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M40.30 is a billable ICD-10-CM diagnosis code for flatback syndrome, site unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 456 through 458, 551 through 552. Coders also document this condition as flatback syndrome. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Scoliosis and other postural dorsopathic deformities.

Code Identity

ICD-10-CM Code
M40.30
Billable Status
Yes — Valid for Submission
Code Describes
Flatback syndrome, site unspecified
Short Description
Flatback syndrome, site unspecified
Same as the full description in the CMS dataset.
Parent Code
M40.3
Flatback syndrome

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM40-M43Deforming dorsopathies
CategoryM40Kyphosis and lordosis
This CodeM40.30Flatback syndrome, site unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Flatback syndrome
  • Flattened lordosis
  • Lordosis deformity of lumbar spine
  • Lordosis finding
  • Loss of lumbar lordosis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Flatback syndrome

Clinical ClassificationClinical

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

CCSR MUS022
Scoliosis and other postural dorsopathic deformities
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Spine Injuries and Disorders

Your backbone, or spine, is made up of 26 bone discs called vertebrae. The vertebrae protect your spinal cord and allow you to stand and bend. A number of problems can change the structure of the spine or damage the vertebrae and surrounding tissue. They include:

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert M40.30 to ICD-9-CMHistory

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

ICD-9-CM
737.19 Kyphosis NEC
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 M40.30Overview

Is M40.30 (Flatback syndrome) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report flatback syndrome, site unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M40.30 group to?

When flatback syndrome, site unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 456, 457, 458, 551, 552, with relative weights from 0.9613 to 8.4034 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M40.30?

Under the General Equivalence Mappings, flatback syndrome, site unspecified converts to ICD-9-CM 737.19 (kyphosis NEC). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.