ICD-10-CM 2027 diagnosis code

M18Osteoarthritis of first carpometacarpal joint

Not billable — use a more specific code

M18 is a header code, so it can't be reported by itself. Choose one of the 7 more specific codes beneath it.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About M18

M18 is the ICD-10-CM diagnosis code for osteoarthritis of first carpometacarpal joint. It belongs to block M15-M19 (osteoarthritis) and chapter 13 (diseases of the musculoskeletal system and connective tissue). It is a header code, so it can't be reported by itself; one of its 7 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: M18.0 (joints), M18.1 (joint), M18.2 (joints), M18.3 (joint), M18.4 (joints), M18.5 (joint) and M18.9 (unspecified).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under M18

Notes that apply from higher levels

Instructions written at a parent level also apply to M18.

Broader instructions also apply from M15-M19 Osteoarthritis and Chapter 13: Diseases of the musculoskeletal system and connective tissue.

Code history

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2027

FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
No changes since FY2016.

Common questions about M18

Is M18 billable?: No. M18 is a header code. Report one of its more specific subcodes instead.