M13.172 (Monoarthritis, not elsewhere classified, left ankle and foot) compared with M13.179 (Monoarthritis, not elsewhere classified, unspecified ankle and foot), from the official CMS tabular data. M13.172 and M13.179 code the same condition on opposite sides.
Same condition; these differ only in which side is documented.
These codes share a category and title and differ only in the side affected. The documentation decides which applies, and a bilateral code is reported only where the code set provides one.
Source: ICD-10-CM tabular list (laterality variant derived from the code title)
Same condition, opposite side. M13.172 and M13.179 name the same condition on opposite sides of the body.
Same category and title, differing only in which side is affected — the documentation decides which one applies, and a bilateral code is reported only where the code set provides one.
| M13.172Monoarthritis, not elsewhere classified, left ankle and foot | M13.179Monoarthritis, not elsewhere classified, unspecified ankle and foot | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | M00-M99 — Diseases of the Musculoskeletal System and Connective Tissue (M00-M99) | M00-M99 — Diseases of the Musculoskeletal System and Connective Tissue (M00-M99) |
| Definition | Monoarthritis, not elsewhere classified, left ankle and foot is a billable ICD-10-CM diagnosis code (M13.172). | Monoarthritis, not elsewhere classified, unspecified ankle and foot is a billable ICD-10-CM diagnosis code (M13.179). |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources