2021 ICD-10-CM Code M45

Ankylosing spondylitis

Version 2021
Non-Billable Code

Not Valid for Submission

M45 is a "header" nonspecific 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 valid for the year 2021 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.

ICD-10:M45
Short Description:Ankylosing spondylitis
Long Description:Ankylosing spondylitis

Code Classification

Specific Coding for Ankylosing spondylitis

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

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

Tabular List of Diseases and Injuries

The Tabular List of Diseases and Injuries is a list of ICD-10 codes, organized "head to toe" into chapters and sections with guidance for inclusions, exclusions, descriptions and more. The following references are applicable to the code M45:


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.

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.

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.

Clinical Information

Information for Patients


Ankylosing Spondylitis

Also called: Rheumatoid spondylitis

Ankylosing spondylitis is a type of arthritis of the spine. It causes inflammation between your vertebrae, which are the bones that make up your spine, and in the joints between your spine and pelvis. In some people, it can affect other joints.

AS is more common and more severe in men. It often runs in families. The cause is unknown, but it is likely that both genes and factors in the environment play a role.

Early symptoms of AS include back pain and stiffness. These problems often start in late adolescence or early adulthood. Over time, AS can fuse your vertebrae together, limiting movement. Some people have symptoms that come and go. Others have severe, ongoing pain.

A diagnosis of AS is based on your medical history and a physical examination. You may also have imaging or blood tests.

AS has no cure, but medicines can relieve symptoms and may keep the disease from getting worse. Eating a healthy diet, not smoking, and exercising can also help. In rare cases, you may need surgery to straighten the spine.

NIH: National Institute of Arthritis and Musculoskeletal and Skin Disease


[Learn More]

Ankylosing spondylitis Ankylosing spondylitis is a form of ongoing joint inflammation (chronic inflammatory arthritis) that primarily affects the spine. This condition is characterized by back pain and stiffness that typically appear in adolescence or early adulthood. Over time, back movement gradually becomes limited as the bones of the spine (vertebrae) fuse together. This progressive bony fusion is called ankylosis.The earliest symptoms of ankylosing spondylitis result 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, causing a condition called spondylitis. 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. People with advanced disease are also more prone to fractures of the vertebrae.Ankylosing spondylitis affects the eyes in up to 40 percent of cases, leading to episodes of eye inflammation called acute iritis. Acute iritis causes eye pain and increased sensitivity to light (photophobia). Rarely, ankylosing spondylitis can also cause serious complications involving the heart, lungs, and nervous system.
[Learn More]

Code History

  • 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 (First year ICD-10-CM implemented into the HIPAA code set)