2026 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 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

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
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

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 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About M18Overview

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.