2026 ICD-10-CM Diagnosis Code M65.921Unspecified synovitis and tenosynovitis, right upper arm

ICD-10-CM Codes›M00–M99›M65-M67›M65

ICD-10-CM M65.921
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M65.921 is a billable ICD-10-CM diagnosis code for unspecified synovitis and tenosynovitis, right upper arm. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Tendon and synovial disorders.

Code Identity

ICD-10-CM Code
M65.921
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified synovitis and tenosynovitis, right upper arm
Short Description
Unspecified synovitis and tenosynovitis, right upper arm
Same as the full description in the CMS dataset.
Parent Code
M65.92
Unspecified synovitis and tenosynovitis, upper arm

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM65-M67Disorders of synovium and tendon
CategoryM65Synovitis and tenosynovitis
This CodeM65.921Unspecified synovitis and tenosynovitis, right upper arm

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

Code History & ChangesHistory

Replacement M65.921 replaces the following previously assigned code(s):

  • M65.9 - Synovitis and tenosynovitis, unspecified
FY 2025AddedAdded to the ICD-10-CM code setEffective October 1, 2024.
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About M65.921Overview

Is M65.921 (Unspecified synovitis and tenosynovitis, upper arm) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified synovitis and tenosynovitis, right upper arm on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M65.921 group to?

When unspecified synovitis and tenosynovitis, right upper arm 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.

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.