2026 ICD-10-CM Diagnosis Code M40.55Lordosis, unspecified, thoracolumbar region

ICD-10-CM Codes›M00–M99›M40-M43›M40

ICD-10-CM M40.55
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M40.55 is a billable ICD-10-CM diagnosis code for lordosis, unspecified, thoracolumbar region. 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 hyperlordosis deformity of lumbar spine. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Scoliosis and other postural dorsopathic deformities.

Code Identity

ICD-10-CM Code
M40.55
Billable Status
Yes — Valid for Submission
Code Describes
Lordosis, unspecified, thoracolumbar region
Short Description
Lordosis, unspecified, thoracolumbar region
Same as the full description in the CMS dataset.
Parent Code
M40.5
Lordosis, unspecified

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM40-M43Deforming dorsopathies
CategoryM40Kyphosis and lordosis
This CodeM40.55Lordosis, unspecified, thoracolumbar region

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Hyperlordosis deformity of lumbar spine
  • Hyperlordosis deformity of thoracic and lumbar spine
  • Lordosis deformity of lumbar spine

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

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

Clinical InformationClinical

  • Lordosis

    the anterior concavity in the curvature of the lumbar and cervical spine as viewed from the side. the term usually refers to abnormally increased curvature (hollow back, saddle back, swayback). it does not include lordosis as normal mating posture in certain animals ( = posture + sex behavior, animal).

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 M40.55 to ICD-9-CMHistory

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

ICD-9-CM
737.29 Lordosis NEC
Approximate The match is approximate rather than exact.
ICD-9-CM
737.42 Lordosis in oth dis
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 M40.55Overview

What is the ICD-10 code for lordosis, unspecified, thoracolumbar region?

The ICD-10-CM code for lordosis, unspecified, thoracolumbar region is M40.55 (sometimes written as M4055). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is M40.55 (Lordosis, unspecified) a billable code?

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

What MS-DRG does M40.55 group to?

When lordosis, unspecified, thoracolumbar region 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 M40.55?

Under the General Equivalence Mappings, lordosis, unspecified, thoracolumbar region converts to ICD-9-CM 737.29 (lordosis NEC) and 737.42 (lordosis in oth dis). The mapping is approximate, so confirm the match fits the documentation.