2026 ICD-10-CM Diagnosis Code M11.879Other specified crystal arthropathies, unspecified ankle and foot

ICD-10-CM Codes›M00–M99›M05-M14›M11

ICD-10-CM M11.879
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M11.879 is a billable ICD-10-CM diagnosis code for other specified crystal arthropathies, unspecified ankle and foot. 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 chondrocalcinosis caused by dicalcium phosphate crystals. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Crystal arthropathies (excluding gout).

Code Identity

ICD-10-CM Code
M11.879
Billable Status
Yes — Valid for Submission
Code Describes
Other specified crystal arthropathies, unspecified ankle and foot
Short Description
Oth crystal arthropathies, unspecified ankle and foot
Parent Code
M11.87
Other specified crystal arthropathies, ankle and foot

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM05-M14Inflammatory polyarthropathies
CategoryM11Other crystal arthropathies
This CodeM11.879Other specified crystal arthropathies, unspecified ankle and foot

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Chondrocalcinosis caused by dicalcium phosphate crystals
  • Chondrocalcinosis caused by pyrophosphate crystals
  • Chondrocalcinosis of ankle and foot joint caused by dicalcium phosphate crystals
  • Chondrocalcinosis of ankle and/or foot joint caused by pyrophosphate crystals
  • Chondrocalcinosis of joint of ankle AND/OR foot

Clinical ClassificationClinical

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

CCSR MUS034
Crystal arthropathies (excluding gout)
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Arthritis

If you feel pain and stiffness in your body or have trouble moving around, you might have arthritis. Any disorder that affects the joints is often called arthritis. Joints are places where two bones meet, such as your elbow or knee.

The full article covers:

  • What is arthritis?
  • What are the types of arthritis?
  • What are the symptoms of arthritis?
  • Who is more likely to get arthritis?
  • How is arthritis diagnosed?
  • What are the treatments for arthritis?

Read the full article at MedlinePlus

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

Convert M11.879 to ICD-9-CMHistory

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

ICD-9-CM
712.87 Cryst arthrop NEC-ankle
Approximate The match is approximate rather than exact.
ICD-9-CM
712.97 Cryst arthrop NOS-ankle
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 M11.879Overview

Is M11.879 (Other specified crystal arthropathies, ankle and foot) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other specified crystal arthropathies, unspecified ankle and foot on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M11.879 group to?

When other specified crystal arthropathies, unspecified ankle and foot 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 M11.879?

Under the General Equivalence Mappings, other specified crystal arthropathies, unspecified ankle and foot converts to ICD-9-CM 712.87 (cryst arthrop NEC-ankle) and 712.97 (cryst arthrop NOS-ankle). 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.