2026 ICD-10-CM Diagnosis Code M21.159Varus deformity, not elsewhere classified, unspecified hip

ICD-10-CM Codes›M00–M99›M20-M25›M21

ICD-10-CM M21.159
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M21.159 is a billable ICD-10-CM diagnosis code for varus deformity, not elsewhere classified, unspecified hip. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 564 through 566. Coders also document this condition as varus deformity of hip. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acquired deformities (excluding foot).

Code Identity

ICD-10-CM Code
M21.159
Billable Status
Yes — Valid for Submission
Code Describes
Varus deformity, not elsewhere classified, unspecified hip
Short Description
Varus deformity, not elsewhere classified, unspecified hip
Same as the full description in the CMS dataset.
Parent Code
M21.15
Varus deformity, not elsewhere classified, hip

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM21Other acquired deformities of limbs
This CodeM21.159Varus deformity, not elsewhere classified, unspecified hip

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Varus deformity of hip

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MUS023
Acquired deformities (excluding foot)
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Hip Injuries and Disorders

Your hip is the joint where your femur (thigh bone) meets your pelvis (hip bone). There are two main parts: a ball at the end of the femur, which fits in a socket in the pelvis. Your hip is known as a ball-and-socket joint. This is because you have a ball at the end of your femur, and it fits into a socket in your pelvis.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert M21.159 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
736.32 Coxa vara
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Revised Code M21.159 was revised for FY 2026, effective October 1, 2025.

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentRevised in the current code setEffective October 1, 2025 through September 30, 2026.

Questions About M21.159Overview

Is M21.159 (Varus deformity, not elsewhere classified, hip) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report varus deformity, not elsewhere classified, unspecified hip on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M21.159 group to?

When varus deformity, not elsewhere classified, unspecified hip is the principal diagnosis on an inpatient stay, it groups to MS-DRG 564, 565, 566, with relative weights from 0.7493 to 1.5436 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M21.159?

Under the General Equivalence Mappings, varus deformity, not elsewhere classified, unspecified hip converts to ICD-9-CM 736.32 (coxa vara). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.