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M45 ICD-10-CM Code: Ankylosing spondylitis

Compare with another code for M45Check this code on a claim

Billing Status: NO. This is a non-billable ICD-10-CM code: report a more specific billable code beneath it.

Coding at a Glance

Official instructions
1 inclusion term · 2 Excludes1 · 1 Excludes2

What these terms mean →

Category · FY2027A non-billable heading in the tabular list: report a more specific code beneath it.

What you need to know

Source: CMS/NCHS Official ICD-10-CM tabular notes, quoted. From the CMS/NCHS tabular list for the release in force. A note the category or block publishes applies to this code too, and is marked with where it comes from.

Excludes1Not reported with this code unless documented as unrelated
  • arthropathy in Reiter's disease (M02.3-)
  • juvenile (ankylosing) spondylitis (M08.1)
Excludes2Not included here; may be reported together
  • Behçet's disease (M35.2)
IncludesWhat this code covers
  • Rheumatoid arthritis of spine

Where it sits Source: CMS/NCHS

Under:Chapter 13: Diseases of the Musculoskeletal System and Connective TissueM40-M54 DorsopathiesM45-M49 Spondylopathies

Codes under M45 (11)

  • M45.0Ankylosing spondylitis of multiple sites in spineBillable
  • M45.1Ankylosing spondylitis of occipito-atlanto-axial regionBillable
  • M45.2Ankylosing spondylitis of cervical regionBillable
  • M45.3Ankylosing spondylitis of cervicothoracic regionBillable
  • M45.4Ankylosing spondylitis of thoracic regionBillable
  • M45.5Ankylosing spondylitis of thoracolumbar regionBillable
  • M45.6Ankylosing spondylitis lumbar regionBillable
  • M45.7Ankylosing spondylitis of lumbosacral regionBillable
  • M45.8Ankylosing spondylitis sacral and sacrococcygeal regionBillable
  • M45.9Ankylosing spondylitis of unspecified sites in spineBillable
  • M45.ANon-radiographic axial spondyloarthritisNot billable

Most relevant related codes MedCoder-derived

Read off the official notes above and this code’s own position in the tabular list. Which to report is a documentation question; Compare shows the two side by side.

CompareCheck ClaimView Related Codes

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for M45 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2027Effective: October 1, 2026

Trace:FY2027 changesChange historyRelease, file and checksum

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Rheumatoid arthritis of spine

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Coder workflow for M45

MedCoder structured workflow — derived from this code’s own official record

Before you code M45

  1. M45 is not reportable as written. Select the more specific code beneath it that the documentation supports. Codes are reported to the highest level of specificity the classification provides (Guidelines I.B.2).

    ReviewM45.0, M45.1, M45.2, M45.3, M45.4, M45.5, M45.6, M45.7, M45.8, M45.9, M45.A

    See the relationships section · Guide: How to choose an ICD-10-CM code →

  2. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with the code beneath M45. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support one of the more specific codes beneath M45?
    Yes → Select that code and continue the checks below on its own page.
    No → M45 cannot be reported as written. Where the codes beneath it include an unspecified code, that code applies when the record goes no further; otherwise query for the missing detail.

    ReviewM45.0, M45.1, M45.2, M45.3, M45.4, M45.5, M45.6, M45.7, M45.8, M45.9, M45.A

  2. Does the documentation support a condition named in M45’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewM02.3, M08.1

Report the code beneath M45 that the documentation supports, not M45 itself. Then confirm that code is valid for the date of service on its own page.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Official instructions as workflow

  • Excludes1 — check before selecting M45(2 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with M45: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareM02.3, M08.1

    See the official tabular notes · Guidelines I.A.12.a

  • Excludes2 — not part of M45(1 note)

    Coding workflow: The conditions named in this note are not included in M45. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareM35.2

    See the official tabular notes · Guidelines I.A.12.b

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: Both the condition M45 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewM02.3, M08.1

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Don’t confuse M45 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of M45 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

  • M02.3— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of arthropathy in Reiter's disease moves the case to M02.3; the two are not reported together unless documented as unrelated.

    Full comparison: M45 vs M02.3 →

  • M08.1— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of juvenile (ankylosing) spondylitis moves the case to M08.1; the two are not reported together unless documented as unrelated.

    Full comparison: M45 vs M08.1 →

  • M35.2— Excludes2 relationship (Informational)

    Distinct conditions — both may be reported.

    A distinct condition — both may be reported when both are documented.

    What moves you there: Documentation of Behçet's disease adds M35.2; it is not part of this code and both may be reported when both are documented.

    Full comparison: M45 vs M35.2 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Coding context

Guidelines, coding notes, decision aids, relationships (with MS-DRG and CCSR classification), hierarchy, HCC, coverage and the context map: what a coder reaches for after the core. Each section names whether it is official source data, a MedCoder-derived relationship or MedCoder editorial.

Code Overview

Ankylosing spondylitis is a non-billable ICD-10-CM category code (M45). A more specific billable subcode must be selected for claims submission.

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Verify Before Coding

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder-derived relationships — computed from published CMS and AHRQ datasets

Other codes that name M45 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 2 Excludes1 notes across 2 chapters: G55 — Nerve root and plexus compressions in diseases classified elsewhere, M05 — Rheumatoid arthritis with rheumatoid factor.

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 7 Excludes2 notes: M20 — Acquired deformities of fingers and toes, M20-M25 — Other joint disorders (M20-M25), M21 — Other acquired deformities of limbs, M22 — Disorder of patella, M23 — Internal derangement of knee, M24 — Other specific joint derangements, M25 — Other joint disorder, not elsewhere classified.

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Referenced by 1 Code First instruction: J99 — Respiratory disorders in diseases classified elsewhere.

Each of these codes carries a Code First note naming this condition — when that code is reported, THIS code is sequenced first, ahead of it.

Contextual Map

Every relationship of M45 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run M45 with these 13 related codes in Claim Check

Hierarchy

Excludes1

Excludes2

Referenced by Excludes1 notes

Referenced by Excludes2 notes

Referenced by Code First instructions

Nearest codes (21)

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Reference

Index terms and tables, published questions and FAQ, every source behind this page with its release and checksum, the date-of-service check and the complete change history.

Common coding questions

MedCoder editorial

Can M45 be billed directly?

No. M45 (Ankylosing spondylitis) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 2026) Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder-derived relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder editorial explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Labels on this page: Official source data · MedCoder-derived relationship · MedCoder editorial explanation. How to read the labels · All data sources and release dates · CMS coding rules

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "M45 — Ankylosing spondylitis." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/m45-ankylosing-spondylitis

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Ankylosing spondylitis

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027, and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to M45 in its code family, with their registry titles.