2026 ICD-10-CM Diagnosis Code M19.91Primary osteoarthritis, unspecified site

ICD-10-CM Codes›M00–M99›M15-M19›M19

ICD-10-CM M19.91
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M19.91 is a billable ICD-10-CM diagnosis code for primary osteoarthritis, unspecified site. 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 localized, primary osteoarthritis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Osteoarthritis.

Code Identity

ICD-10-CM Code
M19.91
Billable Status
Yes — Valid for Submission
Code Describes
Primary osteoarthritis, unspecified site
Short Description
Primary osteoarthritis, unspecified site
Same as the full description in the CMS dataset.
Parent Code
M19.9
Osteoarthritis, unspecified site

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM15-M19Osteoarthritis
CategoryM19Other and unspecified osteoarthritis
This CodeM19.91Primary osteoarthritis, unspecified site

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Localized, primary osteoarthritis
  • Localized, primary osteoarthritis of the pelvic region and thigh
  • Primary localized osteoarthrosis of multiple sites
  • Primary localized osteoarthrosis of pelvic region

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Primary osteoarthritis NOS

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Osteoarthritis
      • primary

Clinical ClassificationClinical

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

CCSR MUS006
Osteoarthritis
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Osteoarthritis

Osteoarthritis, sometimes called OA, is a type of arthritis that only affects the joints, usually in the hands, knees, hips, neck, and lower back. It's the most common type of arthritis.

The full article covers:

  • What is osteoarthritis?
  • What are the symptoms of osteoarthritis?
  • What causes osteoarthritis?
  • Who is more likely to develop osteoarthritis?
  • How is osteoarthritis diagnosed?
  • What are the treatments for osteoarthritis?

Read the full article at MedlinePlus

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

Convert M19.91 to ICD-9-CMHistory

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

ICD-9-CM
715.10 Loc prim osteoart-unspec
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 M19.91Overview

Is M19.91 (Osteoarthritis, unspecified site) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report primary osteoarthritis, unspecified site on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M19.91 group to?

When primary osteoarthritis, unspecified site 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 M19.91?

Under the General Equivalence Mappings, primary osteoarthritis, unspecified site converts to ICD-9-CM 715.10 (loc prim osteoart-unspec). 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.