2026 ICD-10-CM Diagnosis Code M21.759Unequal limb length (acquired), unspecified femur

ICD-10-CM Codes›M00–M99›M20-M25›M21

ICD-10-CM M21.759
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M21.759 is a billable ICD-10-CM diagnosis code for unequal limb length (acquired), unspecified femur. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acquired deformities (excluding foot).

Code Identity

ICD-10-CM Code
M21.759
Billable Status
Yes — Valid for Submission
Code Describes
Unequal limb length (acquired), unspecified femur
Short Description
Unequal limb length (acquired), unspecified femur
Same as the full description in the CMS dataset.
Parent Code
M21.75
Unequal limb length (acquired), femur

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM21Other acquired deformities of limbs
This CodeM21.759Unequal limb length (acquired), unspecified femur

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

Leg Injuries and Disorders

Your legs are made up of bones, blood vessels, muscles, and other connective tissue. They are important for motion and standing. Playing sports, running, falling, or having an accident can damage your legs. Common leg injuries include sprains and strains, joint dislocations, and fractures (broken bones).

Read the full article at MedlinePlus

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

Convert M21.759 to ICD-9-CMHistory

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

ICD-9-CM
736.81 Unequal leg length
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 M21.759Overview

Is M21.759 (Unequal limb length (acquired), femur) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unequal limb length (acquired), unspecified femur on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M21.759 group to?

When unequal limb length (acquired), unspecified femur 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 M21.759?

Under the General Equivalence Mappings, unequal limb length (acquired), unspecified femur converts to ICD-9-CM 736.81 (unequal leg length). 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.