2027 ICD-10-CM Diagnosis Code M18.9Osteoarthritis of first carpometacarpal joint, unspecified
ICD-10-CM Codes›M00–M99›M15-M19›M18
- Billable — Valid for Submission
- Chronic Condition
M18.9 is a billable ICD-10-CM diagnosis code for osteoarthritis of first carpometacarpal joint, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 553 through 554. Coders also document this condition as degenerative joint disease of thumb. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Osteoarthritis.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Degenerative joint disease of thumb
- Inflammation of metacarpophalangeal joint
- Osteoarthritis of finger joint
- Osteoarthritis of metacarpophalangeal joint
- Osteoarthritis of metacarpophalangeal joint of finger
- Osteoarthrosis of the carpometacarpal joint of the thumb
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to M18.9: 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.
- 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.
- osteoarthritis of spine (M47.-)
- 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.
- 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 M18.9, its category, or a range that includes it.
Excludes1 5
These codes carry an Excludes1 note naming M18.9: they are not reported together with it, unless the two conditions are unrelated.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
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.
Convert M18.9 to ICD-9-CMHistory
Code HistoryHistory
Questions About M18.9Overview
What is the ICD-10 code for osteoarthritis of first carpometacarpal joint, unspecified?
The ICD-10-CM code for osteoarthritis of first carpometacarpal joint, unspecified is M18.9 (sometimes written as M189). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is M18.9 (Osteoarthritis of first carpometacarpal joint) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report osteoarthritis of first carpometacarpal joint, unspecified on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does M18.9 group to?
When osteoarthritis of first carpometacarpal joint, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 554, 553, with relative weights from 0.8328 to 1.2492 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of M18.9?
Under the General Equivalence Mappings, osteoarthritis of first carpometacarpal joint, unspecified converts to ICD-9-CM 715.34 (loc osteoarth NOS-hand) and 715.94 (osteoarthros NOS-hand). The mapping is approximate, so confirm the match fits the documentation.
