2027 ICD-10-CM Diagnosis Code M18Osteoarthritis of first carpometacarpal joint

ICD-10-CM Codes›M00–M99›M15-M19›M18

ICD-10-CM M18
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

M18 is a non-billable ICD-10-CM category code for osteoarthritis of first carpometacarpal joint, so it cannot be submitted on claims. Use a more specific code from this category instead, such as M18.0, M18.10, M18.11, and M18.12.

Code Identity

ICD-10-CM Code
M18
Billable Status
No — Non-Billable Category
Code Describes
Osteoarthritis of first carpometacarpal joint
Short Description
Osteoarthritis of first carpometacarpal joint
Same as the full description in the CMS dataset.
Chapter
M15-M19
Osteoarthritis

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM15-M19Osteoarthritis
CategoryM18Osteoarthritis of first carpometacarpal joint
This CodeM18Osteoarthritis of first carpometacarpal joint

Specific Coding for Osteoarthritis of first carpometacarpal jointOverview

Non-specific codes like M18 require more characters. Use one of these billable codes instead:

  • Use M18.0 for Bilateral primary osteoarthritis of first carpometacarpal joints

  • M18.1 for Unilateral primary osteoarthritis of first carpometacarpal joint

  • Use M18.10 for Unilateral primary osteoarthritis of first carpometacarpal joint, unspecified hand

  • Use M18.11 for Unilateral primary osteoarthritis of first carpometacarpal joint, right hand

  • Use M18.12 for Unilateral primary osteoarthritis of first carpometacarpal joint, left hand

  • Use M18.2 for Bilateral post-traumatic osteoarthritis of first carpometacarpal joints

  • M18.3 for Unilateral post-traumatic osteoarthritis of first carpometacarpal joint

  • Use M18.30 for Unilateral post-traumatic osteoarthritis of first carpometacarpal joint, unspecified hand

  • Use M18.31 for Unilateral post-traumatic osteoarthritis of first carpometacarpal joint, right hand

  • Use M18.32 for Unilateral post-traumatic osteoarthritis of first carpometacarpal joint, left hand

  • Use M18.4 for Other bilateral secondary osteoarthritis of first carpometacarpal joints

  • M18.5 for Other unilateral secondary osteoarthritis of first carpometacarpal joint

  • Use M18.50 for Other unilateral secondary osteoarthritis of first carpometacarpal joint, unspecified hand

  • Use M18.51 for Other unilateral secondary osteoarthritis of first carpometacarpal joint, right hand

  • Use M18.52 for Other unilateral secondary osteoarthritis of first carpometacarpal joint, left hand

  • Use M18.9 for Osteoarthritis of first carpometacarpal joint, unspecified

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to M18: its own notes plus those printed at block M00-M25, block M15-M19, and Chapter 13. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Block M00-M25 applies to 2,249 codes
  • Disorders affecting predominantly peripheral (limb) joints

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Block M15-M19 Osteoarthritis applies to 98 codes
  • osteoarthritis of spine (M47.-)
From Chapter 13 (M00-M99) Diseases of the musculoskeletal system and connective tissue applies to 6,687 codes
  • arthropathic psoriasis (L40.5-)
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • compartment syndrome (traumatic) (T79.A-)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Notes

General instructions on how these codes are used.

From Chapter 13 (M00-M99) Diseases of the musculoskeletal system and connective tissue applies to 6,687 codes
  • Use an external cause code following the code for the musculoskeletal condition, if applicable, to identify the cause of the musculoskeletal condition

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name M18, its category, or a range that includes it.

Excludes1 5

These codes carry an Excludes1 note naming M18: they are not reported together with it, unless the two conditions are unrelated.

  • M12 Other and unspecified arthropathy
    arthrosis (M15-M19) names M15-M19, which includes this code
  • M13 Other arthritis
    arthrosis (M15-M19) names M15-M19, which includes this code
  • M13 Other arthritis
    osteoarthritis (M15-M19) names M15-M19, which includes this code
  • M13.8 Other specified arthritis
    osteoarthritis (M15-M19) names M15-M19, which includes this code
  • M15 Polyosteoarthritis
    bilateral involvement of single joint (M16-M19) names M16-M19, which includes this code

Patient EducationClinical

Osteoarthritis

Osteoarthritis, sometimes called OA, is a type of arthritis that only affects the joints, usually in the hands, knees, hips, neck, and lower back. It's the most common type of arthritis.

The full article covers:

  • What is osteoarthritis?
  • What are the symptoms of osteoarthritis?
  • What causes osteoarthritis?
  • Who is more likely to develop osteoarthritis?
  • How is osteoarthritis diagnosed?
  • What are the treatments for osteoarthritis?

Read the full article at MedlinePlus

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

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About M18Overview

What is the ICD-10 code for osteoarthritis of first carpometacarpal joint?

M18 is the ICD-10-CM category for osteoarthritis of first carpometacarpal joint, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is M18 (Osteoarthritis of first carpometacarpal joint) a billable code?

No. This is a category header that groups the codes for osteoarthritis of first carpometacarpal joint, and headers cannot be submitted on claims. Claims for osteoarthritis of first carpometacarpal joint need a more specific code from this category, such as M18.0, M18.10, and M18.11.