M18.9
Billable codeOsteoarthritis of first carpometacarpal joint, unspecified
The ICD-10 code for osteoarthritis of first carpometacarpal joint, unspecified is M18.9.
Documentation support
General coding-documentation guidance — not a substitute for payer-specific requirements or professional coding judgment.
- •This code describes an unspecified presentation. If the medical record documents a more specific detail (e.g. laterality, type, or affected site), a more specific sibling code should be used instead — see Related codes below.
- •Laterality-specific codes exist for this condition — confirm the affected side is documented.
- •As a general rule, code to the highest level of specificity supported by the documentation in the medical record.
Related codes in this category
- M18.0Bilateral primary osteoarthritis of first carpometacarpal joints
- M18.1Unilateral primary osteoarthritis of first carpometacarpal jointnon-billable header
- M18.2Bilateral post-traumatic osteoarthritis of first carpometacarpal joints
- M18.3Unilateral post-traumatic osteoarthritis of first carpometacarpal jointnon-billable header
- M18.4Other bilateral secondary osteoarthritis of first carpometacarpal joints
- M18.5Other unilateral secondary osteoarthritis of first carpometacarpal jointnon-billable header
- M18.9Osteoarthritis of first carpometacarpal joint, unspecified
ICD-9-CM equivalent
Informational only — GEM mappings are approximate, not guaranteed one-to-one equivalents. Verify before use in billing.
- 71534Approximate match
- 71594Approximate match
Associated MS-DRGs
M18.9 can serve as the principal diagnosis for these Medicare Severity Diagnosis-Related Groups.
Informational only — actual DRG assignment also depends on procedures, complications/comorbidities (CC/MCC), discharge status, and payer-specific rules not reflected here.