2026 ICD-10-CM Diagnosis Code M02.861Other reactive arthropathies, right knee

ICD-10-CM Codes›M00–M99›M00-M02›M02

ICD-10-CM M02.861
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M02.861 is a billable ICD-10-CM diagnosis code for other reactive arthropathies, right knee. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 548 through 550. The code is a manifestation code that cannot be reported as the principal diagnosis. Coders also document this condition as reactive arthritis of bilateral knees. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Immune-mediated/reactive arthropathies.

Code Identity

ICD-10-CM Code
M02.861
Billable Status
Yes — Valid for Submission
Code Describes
Other reactive arthropathies, right knee
Short Description
Other reactive arthropathies, right knee
Same as the full description in the CMS dataset.
Parent Code
M02.86
Other reactive arthropathies, knee

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM00-M02Infectious arthropathies
CategoryM02Postinfective and reactive arthropathies
This CodeM02.861Other reactive arthropathies, right knee

Code EditsBilling

Medicare Code Editor checks that affect claim validity for M02.861.

Manifestation diagnoses
Manifestation codes describe the manifestation of an underlying disease, not the disease itself, and therefore should not be used as a principal diagnosis.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Reactive arthritis of bilateral knees
  • Reactive arthritis of joint of knee
  • Reactive arthritis of left knee
  • Reactive arthritis of right knee

Clinical ClassificationClinical

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

CCSR MUS008
Immune-mediated/reactive arthropathies
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Infectious Arthritis

Most kinds of arthritis cause pain and swelling in your joints. Joints are places where two bones meet, such as your elbow or knee. Infectious arthritis is an infection in the joint. The infection comes from a bacterial, viral, or fungal infection that spreads from another part of the body. Symptoms of infectious arthritis include:

Read the full article at MedlinePlus

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

Convert M02.861 to ICD-9-CMHistory

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

ICD-9-CM
711.46 Bact arthritis-l/leg
Approximate The match is approximate rather than exact.
ICD-9-CM
711.56 Viral arthritis-l/leg
Approximate The match is approximate rather than exact.
ICD-9-CM
711.86 Inf arthritis NEC-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 M02.861Overview

Is M02.861 (Other reactive arthropathies, knee) a billable code?

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

What MS-DRG does M02.861 group to?

On inpatient claims, other reactive arthropathies, right knee maps to MS-DRG 548, 549, 550, with relative weights from 0.8741 to 1.9309 depending on complications. Higher weights mean higher Medicare reimbursement.

Can M02.861 be a principal diagnosis?

No. This is a manifestation code: other reactive arthropathies, right knee describes the manifestation of an underlying disease rather than the disease itself, so the underlying condition is sequenced first.

What is the ICD-9 equivalent of M02.861?

Under the General Equivalence Mappings, other reactive arthropathies, right knee converts to ICD-9-CM 711.46 (bact arthritis-l/leg), 711.56 (viral arthritis-l/leg), and 711.86 (inf arthritis NEC-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.