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  6. 2026 ICD-10-CM Code M45

2026 ICD-10-CM Diagnosis Code M45

Ankylosing spondylitis

ICD-10-CM Code:
M45
ICD-10 Code for:
Ankylosing spondylitis
Is Billable?
Not Valid for Submission
Code Navigator:

M45 is a non-specific and non-billable diagnosis code code, consider using a code with a higher level of specificity for a diagnosis of ankylosing spondylitis. The code is not specific and is NOT valid for the year 2026 for the submission of HIPAA-covered transactions. Category or Header define the heading of a category of codes that may be further subdivided by the use of 4th, 5th, 6th or 7th characters.

Specific Coding Applicable to Ankylosing spondylitis

Non-specific codes like M45 require more digits to indicate the appropriate level of specificity. Consider using any of the following ICD-10-CM codes with a higher level of specificity when coding for ankylosing spondylitis:

  • Use M45.0 for Ankylosing spondylitis of multiple sites in spine - BILLABLE CODE

  • Use M45.1 for Ankylosing spondylitis of occipito-atlanto-axial region - BILLABLE CODE

  • Use M45.2 for Ankylosing spondylitis of cervical region - BILLABLE CODE

  • Use M45.3 for Ankylosing spondylitis of cervicothoracic region - BILLABLE CODE

  • Use M45.4 for Ankylosing spondylitis of thoracic region - BILLABLE CODE

  • Use M45.5 for Ankylosing spondylitis of thoracolumbar region - BILLABLE CODE

  • Use M45.6 for Ankylosing spondylitis lumbar region - BILLABLE CODE

  • Use M45.7 for Ankylosing spondylitis of lumbosacral region - BILLABLE CODE

  • Use M45.8 for Ankylosing spondylitis sacral and sacrococcygeal region - BILLABLE CODE

  • Use M45.9 for Ankylosing spondylitis of unspecified sites in spine - BILLABLE CODE

  • M45.A for Non-radiographic axial spondyloarthritis - NON-BILLABLE CODE

  • Use M45.A0 for Non-radiographic axial spondyloarthritis of unspecified sites in spine - BILLABLE CODE

  • Use M45.A1 for Non-radiographic axial spondyloarthritis of occipito-atlanto-axial region - BILLABLE CODE

  • Use M45.A2 for Non-radiographic axial spondyloarthritis of cervical region - BILLABLE CODE

  • Use M45.A3 for Non-radiographic axial spondyloarthritis of cervicothoracic region - BILLABLE CODE

  • Use M45.A4 for Non-radiographic axial spondyloarthritis of thoracic region - BILLABLE CODE

  • Use M45.A5 for Non-radiographic axial spondyloarthritis of thoracolumbar region - BILLABLE CODE

  • Use M45.A6 for Non-radiographic axial spondyloarthritis of lumbar region - BILLABLE CODE

  • Use M45.A7 for Non-radiographic axial spondyloarthritis of lumbosacral region - BILLABLE CODE

  • Use M45.A8 for Non-radiographic axial spondyloarthritis of sacral and sacrococcygeal region - BILLABLE CODE

  • Use M45.AB for Non-radiographic axial spondyloarthritis of multiple sites in spine - BILLABLE CODE

Code Classification

  • Diseases of the musculoskeletal system and connective tissue
    M00–M99
    • Spondylopathies
      M45-M49
      • Ankylosing spondylitis
        M45

Tabular List of Diseases and Injuries

The following annotation back-references are applicable to this diagnosis code. The Tabular List of Diseases and Injuries is a list of ICD-10-CM codes, organized "head to toe" into chapters and sections with coding notes and guidance for inclusions, exclusions, descriptions and more.


Inclusion Terms

Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
  • Rheumatoid arthritis of spine

Type 1 Excludes

Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
  • arthropathy in Reiter's disease M02.3
  • juvenile ankylosing spondylitis M08.1

Type 2 Excludes

Type 2 Excludes
A type 2 excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.
  • Behçet's disease M35.2

Patient Education


Ankylosing Spondylitis

What is ankylosing spondylitis?

Ankylosing spondylitis (AS) is a type of arthritis of the spine. It causes inflammation (swelling) between your vertebrae (the bones that make up your spine) and the joints between your spine and pelvis. AS inflammation can cause stiffness and make it difficult to move and bend.

Symptoms of AS can range from mild to severe back pain. Over time, AS can fuse (grow together) your vertebrae, limiting movement and causing a hunched posture. In some people, AS can affect other joints or body parts.

There is no cure for AS, but early treatment can help manage symptoms, slow down the disease, and help you lead a more productive life.

Who is more likely to get ankylosing spondylitis?

Ankylosing spondylitis usually starts before age 45. Early symptoms may begin between the ages of 15 and 30. Your chance of developing AS can also increase if:

  • You're a man. AS is more common and severe in men.
  • You have a family history. If a member of your family has AS, you're more likely to get the disease.
  • You have other medical conditions that may increase your risk of getting AS. These include Crohn's disease, ulcerative colitis, or psoriasis.

What causes ankylosing spondylitis?

No one knows what causes ankylosing spondylitis, but the environment and genes likely play a role. Your genes are parts of DNA in your cells that are passed down from your parents. Certain genes may increase your risk of getting the disease, but not everyone with these genes gets AS.

What are the symptoms of ankylosing spondylitis?

AS affects people differently. The most common symptom is pain and stiffness in the lower back and/or hips. The pain is usually worse during the night or after sitting for a long time.

Over time, AS may progress to other areas of your spine or body. Symptoms may depend on which areas of your body the disease affects. Some people have symptoms that come and go. Others may have severe, ongoing pain.

Other symptoms of ankylosing spondylitis may include:

  • Pain, stiffness, and inflammation of the joints.
  • Difficulty taking a deep breath. This could occur if the joints connecting the ribs are affected.
  • Changes in vision.
  • Fatigue.
  • Loss of appetite.
  • Weight loss.
  • Skin rashes, such as psoriasis.
  • Abdominal (belly) pain and loose stools (poop).

How is ankylosing spondylitis diagnosed?

There is no single test for ankylosing spondylitis. To find out if you have AS your health care provider may:

  • Ask about your medical history, including your symptoms.
  • Ask about your family health history, including relatives who have had AS.
  • Do a physical exam.
  • Order blood tests or imaging studies.

What are the treatments for ankylosing spondylitis?

AS has no cure, but treatment may help relieve symptoms, maintain posture, and slow down the disease. Since other parts of your body can be affected by AS, you will likely work with a team of health care professionals for tests, diagnosis, and care.

Treatment usually includes medicine to help relieve symptoms and keep the disease from getting worse, as well as physical therapy to improve mobility. If AS is severe, surgery may be needed.

You can help manage your AS symptoms if you:

  • Exercise
  • Monitor your symptoms
  • Manage your stress
  • Use assistive devices as needed
  • Follow a healthy diet
  • Stop smoking, or don't start

NIH: National Institute of Arthritis and Musculoskeletal and Skin Disease


[Learn More in MedlinePlus]

Ankylosing spondylitis

Ankylosing spondylitis is a form of painful, ongoing joint inflammation (chronic inflammatory arthritis) that primarily affects the spine.  Early symptoms of ankylosing spondylitis typically begin between the ages of 15 and 30. Most commonly, affected individuals first experience chronic back pain and stiffness. This pain worsens with rest or inactivity, and tends to be relieved with physical activity or exercise.

Pain in ankylosing spondylitis results from inflammation of the joints between the pelvic bones (the ilia) and the base of the spine (the sacrum). These joints are called sacroiliac joints, and inflammation of these joints is known as sacroiliitis. The inflammation gradually spreads to the joints between the vertebrae, eventually involving the whole spine, causing a condition called spondylitis. Over time, back movement gradually becomes limited as the bones of the spine (vertebrae) fuse together. This progressive bony fusion is called ankylosis. These fused bones are prone to fracture.

Ankylosing spondylitis can involve other joints as well, including the shoulders, hips, and, less often, the knees. As the disease progresses, it can affect the joints between the spine and ribs, restricting movement of the chest and making it difficult to breathe deeply. 

Ankylosing spondylitis affects the eyes in more than 30 percent of cases, leading to episodes of eye inflammation called acute iritis. Acute iritis typically affects one eye at a time and causes eye pain and increased sensitivity to light (photophobia). Rarely, ankylosing spondylitis can also cause serious complications involving the heart, lungs, and nervous system. Six to 10 percent of people with ankylosing spondylitis have additional inflammatory disorders such as psoriasis, which affects the skin, or ulcerative colitis or Crohn's disease, which both affect the digestive tract.


[Learn More in MedlinePlus]

Ankylosing Spondylitis

Ankylosing spondylitis is a type of arthritis that causes inflammation in certain parts of the spine.
[Learn More in MedlinePlus]

Code History

  • FY 2026 - No Change, effective from 10/1/2025 through 9/30/2026
  • FY 2025 - No Change, effective from 10/1/2024 through 9/30/2025
  • FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
  • FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
  • FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.