2026 ICD-10-CM Diagnosis Code M21.169Varus deformity, not elsewhere classified, unspecified knee

ICD-10-CM Codes›M00–M99›M20-M25›M21

ICD-10-CM M21.169
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M21.169 is a billable ICD-10-CM diagnosis code for varus deformity, not elsewhere classified, unspecified knee. 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 acquired genu valgum. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acquired deformities (excluding foot).

Code Identity

ICD-10-CM Code
M21.169
Billable Status
Yes — Valid for Submission
Code Describes
Varus deformity, not elsewhere classified, unspecified knee
Short Description
Varus deformity, not elsewhere classified, unspecified knee
Same as the full description in the CMS dataset.
Parent Code
M21.16
Varus deformity, not elsewhere classified, knee

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM21Other acquired deformities of limbs
This CodeM21.169Varus deformity, not elsewhere classified, unspecified knee

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acquired genu valgum
  • Acquired genu valgum and varum
  • Acquired genu varum
  • Acquired valgus deformity of joint of lower limb
  • Acquired varus deformity of joint of lower limb
  • Bandy legged
  • Knee joint valgus deformity

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

Knee Injuries and Disorders

Your knee joint is made up of bone, cartilage, ligaments and fluid. Muscles and tendons help the knee joint move. When any of these structures is hurt or diseased, you have knee problems. Knee problems can cause pain and difficulty walking.

Read the full article at MedlinePlus

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

Convert M21.169 to ICD-9-CMHistory

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

ICD-9-CM
736.42 Genu varum
Approximate The match is approximate rather than exact.

Code HistoryHistory

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

Questions About M21.169Overview

Is M21.169 (Varus deformity, not elsewhere classified, knee) a billable code?

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

What MS-DRG does M21.169 group to?

When varus deformity, not elsewhere classified, unspecified knee 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 M21.169?

Under the General Equivalence Mappings, varus deformity, not elsewhere classified, unspecified knee converts to ICD-9-CM 736.42 (genu varum). 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.