Is M13.1 a billable ICD-10-CM code?

No. M13.1 is a non-billable header code. Code to a higher level of specificity using one of its child codes.

Where does M13.1 sit in the tabular list?

Diseases of the musculoskeletal system and connective tissue (M00-M99), in the block Inflammatory polyarthropathies (M05-M14).

What cannot be coded together with M13.1?

M13.1 carries Excludes1 notes, which means the conditions they list can never be coded together with it on the same encounter. Some are written on the categories above M13.1 (M13) and apply to it just the same.

M13.1

M13.1 — Monoarthritis, not elsewhere classified

Non-billable headerICD-10-CM

M13.1 is a non-billable header ICD-10-CM code for monoarthritis, not elsewhere classified. It cannot be billed on its own: choose one of the more specific child codes below.

Excludes1 inherited from the categories above M13.1

These are not written on M13.1, but they bind it: a note on a category applies to every code beneath it. Billing M13.1 with anything listed here is a denial.

Written on M13 — Other arthritis

arthrosis (M15-M19)
osteoarthritis (M15-M19)

Risk adjustment

M13.1 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.

Code history

M13.1 has not changed since FY2024 — no addition, revision or deletion across the three most recent ICD-10-CM releases.

Code to one of these instead M13.1

8 child codes. Green means billable.

Related codes at this level

Codes that share M13. If M13.1 is not quite right, the correct code is usually one of these.

Questions about M13.1

Is M13.1 a billable ICD-10-CM code?: No. M13.1 is a non-billable header code. Code to a higher level of specificity using one of its child codes.
Where does M13.1 sit in the tabular list?: Diseases of the musculoskeletal system and connective tissue (M00-M99), in the block Inflammatory polyarthropathies (M05-M14).
What cannot be coded together with M13.1?: M13.1 carries Excludes1 notes, which means the conditions they list can never be coded together with it on the same encounter. Some are written on the categories above M13.1 (M13) and apply to it just the same.