2027 ICD-10-CM Diagnosis Code M25.462Effusion, left knee

ICD-10-CM Codes›M00–M99›M20-M25›M25

ICD-10-CM M25.462
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

M25.462 is a billable ICD-10-CM diagnosis code for effusion, left knee. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) 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
M25.462
Billable Status
Yes — Valid for Submission
Code Describes
Effusion, left knee
Short Description
Effusion, left 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 CodeM25.462Effusion, left 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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to M25.462: its own notes plus those printed at M25.4, M25, block M00-M25, block M20-M25, and Chapter 13. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Block M00-M25 applies to 2,249 codes
  • Disorders affecting predominantly peripheral (limb) joints

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From M25.4 Effusion of joint applies to 26 codes
  • hydrarthrosis in yaws (A66.6)
  • intermittent hydrarthrosis (M12.4-)
  • other infective (teno)synovitis (M65.1-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From M25 Other joint disorder, not elsewhere classified applies to 225 codes
  • abnormality of gait and mobility (R26.-)
  • acquired deformities of limb (M20-M21)
  • calcification of bursa (M71.4-)
  • calcification of shoulder (joint) (M75.3)
  • calcification of tendon (M65.2-)
  • difficulty in walking (R26.2)
  • temporomandibular joint disorder (M26.6-)
From Block M20-M25 Other joint disorders applies to 719 codes
From Chapter 13 (M00-M99) Diseases of the musculoskeletal system and connective tissue applies to 6,687 codes
  • arthropathic psoriasis (L40.5-)
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • compartment syndrome (traumatic) (T79.A-)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Notes

General instructions on how these codes are used.

From Chapter 13 (M00-M99) Diseases of the musculoskeletal system and connective tissue applies to 6,687 codes
  • Use an external cause code following the code for the musculoskeletal condition, if applicable, to identify the cause of the musculoskeletal condition

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name M25.462, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming M25.462: they are not reported together with it, unless the two conditions are unrelated.

  • R22 Localized swelling, mass and lump of skin and subcutaneous tissue
    swelling of joint (M25.4-) names M25.4-, which includes this code

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

Clinical InformationClinical

  • Effusion

    a collection of fluid in a body cavity, which may be the result of a non-neoplastic disorder (e.g. heart failure) or a tumor (e.g. carcinoma of the lung).

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 M25.462 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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About M25.462Overview

What is the ICD-10 code for effusion, left knee?

The ICD-10-CM code for effusion, left knee is M25.462 (sometimes written as M25462). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is M25.462 (Effusion, knee) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report effusion, left knee on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does M25.462 group to?

When effusion, left knee is the principal diagnosis on an inpatient stay, it groups to MS-DRG 564, 566, 565, with relative weights from 0.7374 to 1.4909 depending on complications. Higher weights mean higher Medicare reimbursement.

Can M25.462 be reported with A66.6?

Not as a rule. The Excludes1 note at M25.4, which applies to M25.462, lists "hydrarthrosis in yaws (A66.6)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

What is the ICD-9 equivalent of M25.462?

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