Excludes1 pair
M13.8- vs M19-
M13.8 and M19 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.
The official note, declared on M13.8
osteoarthritis (M15-M19)
M13.8
Other specified arthritis
Not billable
- Chapter 13
- Diseases of the musculoskeletal system and connective tissue
- Section
- M05-M14
Use when the record says
- Allergic arthritis
Indexed under
- Polyarthritis, polyarthropathy › migratory
M19
Other and unspecified osteoarthritis
Not billable
- Chapter 13
- Diseases of the musculoskeletal system and connective tissue
- Section
- M15-M19
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027