2026 ICD-10-CM Diagnosis Code M66.146Rupture of synovium, unspecified finger(s)

ICD-10-CM Codes›M00–M99›M65-M67›M66

ICD-10-CM M66.146
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M66.146 is a billable ICD-10-CM diagnosis code for rupture of synovium, unspecified finger(s). It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 557 through 558. Coders also document this condition as rupture of synovium of finger. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Tendon and synovial disorders.

Code Identity

ICD-10-CM Code
M66.146
Billable Status
Yes — Valid for Submission
Code Describes
Rupture of synovium, unspecified finger(s)
Short Description
Rupture of synovium, unspecified finger(s)
Same as the full description in the CMS dataset.
Parent Code
M66.14
Rupture of synovium, hand and fingers

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM65-M67Disorders of synovium and tendon
CategoryM66Spontaneous rupture of synovium and tendon
This CodeM66.146Rupture of synovium, unspecified finger(s)

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Rupture of synovium of finger
  • Rupture of synovium of hand

Clinical ClassificationClinical

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

CCSR MUS009
Tendon and synovial disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Finger Injuries and Disorders

You use your fingers and thumbs to do everything from grasping objects to playing musical instruments to typing. When there is something wrong with them, it can make life difficult. Common problems include:

Read the full article at MedlinePlus

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

Convert M66.146 to ICD-9-CMHistory

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

ICD-9-CM
727.59 Rupture of synovium NEC
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 M66.146Overview

Is M66.146 (Rupture of synovium, hand and fingers) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report rupture of synovium, unspecified finger(s) on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M66.146 group to?

When rupture of synovium, unspecified finger(s) is the principal diagnosis on an inpatient stay, it groups to MS-DRG 557, 558, with relative weights from 0.8932 to 1.4869 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M66.146?

Under the General Equivalence Mappings, rupture of synovium, unspecified finger(s) converts to ICD-9-CM 727.59 (rupture of synovium NEC). 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.