M66.321 (Spontaneous rupture of flexor tendons, right upper arm) compared with M66.329 (Spontaneous rupture of flexor tendons, unspecified upper arm), from the official CMS tabular data. M66.321 and M66.329 code the same condition on opposite sides. MedCoder-derived
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. M66.321 and M66.329 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.
| M66.321Spontaneous rupture of flexor tendons, right upper arm | M66.329Spontaneous rupture of flexor tendons, unspecified upper arm | |
|---|---|---|
| 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 | Spontaneous rupture of flexor tendons, right upper arm is a billable ICD-10-CM diagnosis code (M66.321). | Spontaneous rupture of flexor tendons, unspecified upper arm is a billable ICD-10-CM diagnosis code (M66.329). |
| Includes | rupture that occurs when a normal force is applied to tissues that are inferred to have less than normal strength | rupture that occurs when a normal force is applied to tissues that are inferred to have less than normal strength |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources