M18.9
Osteoarthritis of first carpometacarpal joint, unspecified
Billable FY2026 2025-10-01 → 2026-09-30
This is the unspecified option. 6 more
specific codes sit alongside it. Worth
checking whether the documentation supports one of them.
Exclusions 10 never code together
M00-M99chapter
Excludes2
- arthropathic psoriasis (L40.5-)L40.5-
- certain conditions originating in the perinatal period (P04-P96)P04-P96
- certain infectious and parasitic diseases (A00-B99)A00-B99
- compartment syndrome (traumatic) (T79.A-)T79.A-
- complications of pregnancy, childbirth and the puerperium (O00-O9A)O00-O9A
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Q00-Q99
- endocrine, nutritional and metabolic diseases (E00-E88)E00-E88
- injury, poisoning and certain other consequences of external causes (S00-T88)S00-T88
- neoplasms (C00-D49)C00-D49
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)R00-R94
Excludes2 — not included here, but the patient may have both. Code both when documented.
Instructional notes 2
Index entries leading here 1
Alongside this code 6 same parent — M18
M18.0 Bilateral primary osteoarth of first carpometacarp joints M18.1 Unilateral primary osteoarth of first carpometacarp joint category M18.2 Bi post-trauma osteoarth of first carpometacarp joints M18.3 Unil post-trauma osteoarth of first carpometacarp joint category M18.4 Oth bi secondary osteoarth of first carpometacarp joints M18.5 Oth unil secondary osteoarth of first carpometacarp joint category
Additional references
AHA Coding Clinic® Licence required
Official coding advice for this code. Published by the American Hospital Association. Not included in this installation.