2026 ICD-10-CM Diagnosis Code M91.42Coxa magna, left hip

ICD-10-CM Codes›M00–M99›M91-M94›M91

ICD-10-CM M91.42
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M91.42 is a billable ICD-10-CM diagnosis code for coxa magna, left hip. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 553 through 554. Coders also document this condition as acquired deformity of left hip. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified bone disease and musculoskeletal deformities.

Code Identity

ICD-10-CM Code
M91.42
Billable Status
Yes — Valid for Submission
Code Describes
Coxa magna, left hip
Short Description
Coxa magna, left hip
Same as the full description in the CMS dataset.
Parent Code
M91.4
Coxa magna

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM91-M94Chondropathies
CategoryM91Juvenile osteochondrosis of hip and pelvis
This CodeM91.42Coxa magna, left hip

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acquired deformity of left hip
  • Acquired deformity of right hip
  • Bilateral acquired deformity of hip regions
  • Bilateral coxa magna
  • Coxa magna
  • Coxa magna of left femur
  • Coxa magna of right femur

Clinical ClassificationClinical

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

CCSR MUS028
Other specified bone disease and musculoskeletal deformities
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Coxa Magna

    deformity of the hip characterized by enlargement and deformation of the femur head and femur neck, often with associated changes in the acetabulum. these changes may be secondary to other diseases (e.g. legg-perthes disease; arthritis; hip dislocation, congenital) or trauma.

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 M91.42 to ICD-9-CMHistory

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

ICD-9-CM
732.1 Juv osteochondros pelvis
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 M91.42Overview

Is M91.42 (Coxa magna) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report coxa magna, left hip on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M91.42 group to?

When coxa magna, left hip is the principal diagnosis on an inpatient stay, it groups to MS-DRG 553, 554, with relative weights from 0.8301 to 1.2963 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M91.42?

Under the General Equivalence Mappings, coxa magna, left hip converts to ICD-9-CM 732.1 (juv osteochondros pelvis). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.