2026 ICD-10-CM Diagnosis Code M66.311Spontaneous rupture of flexor tendons, right shoulder

ICD-10-CM Codes›M00–M99›M65-M67›M66

ICD-10-CM M66.311
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M66.311 is a billable ICD-10-CM diagnosis code for spontaneous rupture of flexor tendons, right shoulder. 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
M66.311
Billable Status
Yes — Valid for Submission
Code Describes
Spontaneous rupture of flexor tendons, right shoulder
Short Description
Spontaneous rupture of flexor tendons, right shoulder
Same as the full description in the CMS dataset.
Parent Code
M66.31
Spontaneous rupture of flexor tendons, shoulder

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM65-M67Disorders of synovium and tendon
CategoryM66Spontaneous rupture of synovium and tendon
This CodeM66.311Spontaneous rupture of flexor tendons, right shoulder

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

Shoulder Injuries and Disorders

Your shoulder joint is composed of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone). Your shoulders are the most movable joints in your body. They can also be unstable because the ball of the upper arm is larger than the shoulder socket that holds it.

Read the full article at MedlinePlus

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

Convert M66.311 to ICD-9-CMHistory

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

ICD-9-CM
727.62 Biceps tendon rupture
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 M66.311Overview

Is M66.311 (Spontaneous rupture of flexor tendons, shoulder) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report spontaneous rupture of flexor tendons, right shoulder on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M66.311 group to?

When spontaneous rupture of flexor tendons, right shoulder 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 M66.311?

Under the General Equivalence Mappings, spontaneous rupture of flexor tendons, right shoulder converts to ICD-9-CM 727.62 (biceps tendon rupture). 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.