2026 ICD-10-CM Diagnosis Code M46.1Sacroiliitis, not elsewhere classified

ICD-10-CM Codes›M00–M99›M45-M49›M46

ICD-10-CM M46.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M46.1 is a billable ICD-10-CM diagnosis code for sacroiliitis, not elsewhere classified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 551 through 552. Coders also document this condition as bilateral sacroiliitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Spondylopathies/spondyloarthropathy (including infective).

Code Identity

ICD-10-CM Code
M46.1
Billable Status
Yes — Valid for Submission
Code Describes
Sacroiliitis, not elsewhere classified
Short Description
Sacroiliitis, not elsewhere classified
Same as the full description in the CMS dataset.
Parent Code
M46
Other inflammatory spondylopathies

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM45-M49Spondylopathies
CategoryM46Other inflammatory spondylopathies
This CodeM46.1Sacroiliitis, not elsewhere classified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Bilateral sacroiliitis
  • Inflammation of sacroiliac joint
  • Sacroiliitis of left sacroiliac joint
  • Sacroiliitis of right sacroiliac joint

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.

    • Change(s) (in) (of)
      • inflammatory
        • sacroiliac
    • Inflammation, inflamed, inflammatory(with exudation)
      • joint NEC
        • sacroiliac
    • Sacroiliitis NEC
    • Spondylitis(chronic)
      • sacroiliac NEC

Clinical ClassificationClinical

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

CCSR MUS011
Spondylopathies/spondyloarthropathy (including infective)
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

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Read the full article at MedlinePlus

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

Convert M46.1 to ICD-9-CMHistory

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

ICD-9-CM
720.2 Sacroiliitis NEC
Exact Match The mapping is direct, with no qualifiers.

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 M46.1Overview

Is M46.1 (Other inflammatory spondylopathies) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report sacroiliitis, not elsewhere classified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M46.1 group to?

When sacroiliitis, not elsewhere classified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 551, 552, with relative weights from 0.9613 to 1.6761 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M46.1?

Under the General Equivalence Mappings, sacroiliitis, not elsewhere classified converts to ICD-9-CM 720.2 (sacroiliitis NEC). The mapping is a direct match.

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.