2026 ICD-10-CM Diagnosis Code M17.12Unilateral primary osteoarthritis, left knee

ICD-10-CM Codes›M00–M99›M15-M19›M17

ICD-10-CM M17.12
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M17.12 is a billable ICD-10-CM diagnosis code for unilateral primary osteoarthritis, left knee. 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 degenerative disorder of articular cartilage of left knee. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Osteoarthritis.

This medical diagnosis code is frequently used in Orthopedics medical specialties to designate conditions such osteoarthritis of the knee.

Code Identity

ICD-10-CM Code
M17.12
Billable Status
Yes — Valid for Submission
Code Describes
Unilateral primary osteoarthritis, left knee
Short Description
Unilateral primary osteoarthritis, left knee
Same as the full description in the CMS dataset.
Parent Code
M17.1
Unilateral primary osteoarthritis of knee

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM15-M19Osteoarthritis
CategoryM17Osteoarthritis of knee
This CodeM17.12Unilateral primary osteoarthritis, left knee

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Degenerative disorder of articular cartilage of left knee
  • Osteoarthritis of left knee joint
  • Osteoarthritis of left patellofemoral joint
  • Patellofemoral osteoarthritis

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 M17.12 to ICD-9-CMHistory

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

ICD-9-CM
715.16 Loc prim osteoart-l/leg
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 M17.12Overview

Is M17.12 (Unilateral primary osteoarthritis of knee) a billable code?

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

What MS-DRG does M17.12 group to?

When unilateral primary osteoarthritis, left knee 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 M17.12?

Under the General Equivalence Mappings, unilateral primary osteoarthritis, left knee converts to ICD-9-CM 715.16 (loc prim osteoart-l/leg). 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.