2026 ICD-10-CM Diagnosis Code M25.461Effusion, right knee

ICD-10-CM Codes›M00–M99›M20-M25›M25

ICD-10-CM M25.461
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M25.461 is a billable ICD-10-CM diagnosis code for effusion, right knee. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 564 through 566. Coders also document this condition as effusion of joint of bilateral knees. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified joint disorders.

Code Identity

ICD-10-CM Code
M25.461
Billable Status
Yes — Valid for Submission
Code Describes
Effusion, right knee
Short Description
Effusion, right knee
Same as the full description in the CMS dataset.
Parent Code
M25.46
Effusion, knee

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM25Other joint disorder, not elsewhere classified
This CodeM25.461Effusion, right knee

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Effusion of joint of bilateral knees
  • Effusion of joint of left knee
  • Effusion of joint of right knee
  • Knee joint effusion

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 M25.461 to ICD-9-CMHistory

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

ICD-9-CM
719.06 Joint effusion-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 M25.461Overview

Is M25.461 (Effusion, knee) a billable code?

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

What MS-DRG does M25.461 group to?

When effusion, right knee is the principal diagnosis on an inpatient stay, it groups to MS-DRG 564, 565, 566, with relative weights from 0.7493 to 1.5436 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M25.461?

Under the General Equivalence Mappings, effusion, right knee converts to ICD-9-CM 719.06 (joint effusion-l/leg). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.