2026 ICD-10-CM Diagnosis Code M12.40Intermittent hydrarthrosis, unspecified site

ICD-10-CM Codes›M00–M99›M05-M14›M12

ICD-10-CM M12.40
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M12.40 is a billable ICD-10-CM diagnosis code for intermittent hydrarthrosis, 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified joint disorders.

Code Identity

ICD-10-CM Code
M12.40
Billable Status
Yes — Valid for Submission
Code Describes
Intermittent hydrarthrosis, unspecified site
Short Description
Intermittent hydrarthrosis, unspecified site
Same as the full description in the CMS dataset.
Parent Code
M12.4
Intermittent hydrarthrosis

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM05-M14Inflammatory polyarthropathies
CategoryM12Other and unspecified arthropathy
This CodeM12.40Intermittent hydrarthrosis, unspecified site

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.

    • Hydrarthrosis
      • intermittent

Clinical ClassificationClinical

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

CCSR MUS007
Other specified joint disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Joint Disorders

Your joints are places where two or more bones come together. Your shoulders, elbows, hips, knees, and knuckles are all joints. Your spine has joints, too.

The full article covers:

  • What are joints?
  • What are joint disorders?
  • What diseases can affect the joints?
  • What types of joint disorders happen from sudden injuries?
  • What types of joint disorders happen from overuse?
  • How can I keep my joints healthy?

Read the full article at MedlinePlus

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

Convert M12.40 to ICD-9-CMHistory

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

ICD-9-CM
719.30 Palindrom rheum-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 M12.40Overview

Is M12.40 (Intermittent hydrarthrosis) a billable code?

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

What MS-DRG does M12.40 group to?

When intermittent hydrarthrosis, 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 M12.40?

Under the General Equivalence Mappings, intermittent hydrarthrosis, unspecified site converts to ICD-9-CM 719.30 (palindrom rheum-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.