2027 ICD-10-CM Diagnosis Code M13.169Monoarthritis, not elsewhere classified, unspecified knee

ICD-10-CM Codes›M00–M99›M05-M14›M13

ICD-10-CM M13.169
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

M13.169 is a billable ICD-10-CM diagnosis code for monoarthritis, not elsewhere classified, unspecified knee. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 553 through 554. Coders also document this condition as inflammation of knee joint. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified joint disorders.

Code Identity

ICD-10-CM Code
M13.169
Billable Status
Yes — Valid for Submission
Code Describes
Monoarthritis, not elsewhere classified, unspecified knee
Short Description
Monoarthritis, not elsewhere classified, unspecified knee
Same as the full description in the CMS dataset.
Parent Code
M13.16
Monoarthritis, not elsewhere classified, knee

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM05-M14Inflammatory polyarthropathies
CategoryM13Other arthritis
This CodeM13.169Monoarthritis, not elsewhere classified, unspecified knee

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Inflammation of knee joint
  • Monoarthritis of knee

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to M13.169: its own notes plus those printed at M13, block M00-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 M13 Other arthritis applies to 47 codes

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 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.

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to 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

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 M13.169 to ICD-9-CMHistory

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

ICD-9-CM
716.66 Monoarthritis NOS-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 M13.169Overview

What is the ICD-10 code for monoarthritis, not elsewhere classified, unspecified knee?

The ICD-10-CM code for monoarthritis, not elsewhere classified, unspecified knee is M13.169 (sometimes written as M13169). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is M13.169 (Monoarthritis, not elsewhere classified, knee) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report monoarthritis, not elsewhere classified, unspecified knee on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does M13.169 group to?

When monoarthritis, not elsewhere classified, unspecified knee is the principal diagnosis on an inpatient stay, it groups to MS-DRG 554, 553, with relative weights from 0.8328 to 1.2492 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M13.169?

Under the General Equivalence Mappings, monoarthritis, not elsewhere classified, unspecified knee converts to ICD-9-CM 716.66 (monoarthritis NOS-l/leg). The mapping is approximate, so confirm the match fits the documentation.