M21.959 Unspecified acquired deformity of unspecified thigh

ICD-10-CM Diagnosis Code M21.959: Unspecified acquired deformity of unspecified thigh

ICD-10-CM code M21.959 designates an unspecified acquired deformity of an unspecified thigh, representing an active concept within the system. It falls under the parent category of unspecified acquired deformities of the thigh. Mapping guidance indicates this code serves as a default target for certain acquired hip deformities when laterality is not specified. 1 2

Plain-language overview

Code M21.959 identifies an acquired abnormality in the thigh, and the terminology record classifies its semantic type specifically as an Acquired Abnormality. 1

What this code represents

The official preferred name for M21.959 is Unspecified acquired deformity of unspecified thigh, and the concept's semantic type is classified as an Acquired Abnormality. 1

M21.959 is an active terminology record that exists as a narrower concept under the parent code M21.95, which denotes an unspecified acquired deformity of the thigh. 1

Coding details

In SNOMED CT to ICD-10-CM mapping, the SNOMED concept for acquired deformity of the hip maps to M21.959 by default, carrying an advice that descendants are not exhaustively mapped. 2

The default mapping to M21.959 was established in agreement with ICD-10-CM guidance, and the map category is assigned as properly classified for the acquired hip deformity source concept. 2

Documentation considerations

When mapping acquired deformity of the hip, an application may display choices to refine the code by specifying right thigh, left thigh, or unspecified thigh if the user provides additional laterality input. 2

The terminology record for M21.959 includes narrower concepts within the hierarchy, indicating that more specific classification options exist beneath this unspecified thigh deformity code. 1

What the sources add

While the terminology record defines M21.959 as an active concept with a parent hierarchy, the mapping specification provides operational context by illustrating how the code functions as a default target for acquired hip deformities. 1 2

The EVS Explore portal confirms the existence of M21.959 as Unspecified acquired deformity of unspecified thigh, showing zero asserted or inherited role relationships pointing from the current concept to others. 3

Sources

1. ICD-10-CM M21.959 terminology record — National Cancer Institute Enterprise Vocabulary Services; accessed 2026-07-27.
2. Mapping SNOMED CT to ICD-10-CM — nlm.nih.gov; accessed 2026-07-27.
3. EVS Explore — evsexplore.semantics.cancer.gov; accessed 2026-07-27.