ICD-10-CM 2027 diagnosis code

M66Spontaneous rupture of synovium and tendon

Not billable — use a more specific code

M66 is a header code, so it can't be reported by itself. Choose one of the 6 more specific codes beneath it.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About M66

M66 is the ICD-10-CM diagnosis code for spontaneous rupture of synovium and tendon. It belongs to block M65-M67 (disorders of synovium and tendon) and chapter 13 (diseases of the musculoskeletal system and connective tissue). It is a header code, so it can't be reported by itself; one of its 6 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: M66.0 (cyst), M66.1 (synovium), M66.2 (tendons), M66.3 (tendons), M66.8 (tendons) and M66.9 (tendon).

The conditions in its Excludes2 note aren't part of M66, but may be coded alongside it if the patient has both: rotator cuff syndrome (M75.1-) and rupture where an abnormal force is applied to normal tissue - see injury of tendon by body region.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under M66

Coding notes

IncludesFurther defines the content of the category

rupture that occurs when a normal force is applied to tissues that are inferred to have less than normal strength

Excludes2Not included here — may be reported together if both conditions exist

rotator cuff syndrome (M75.1-)
rupture where an abnormal force is applied to normal tissue - see injury of tendon by body region

Notes that apply from higher levels

Instructions written at a parent level also apply to M66.

Broader instructions also apply from Chapter 13: Diseases of the musculoskeletal system and connective tissue.

Codes whose notes reference M66

M62.1Excludes2

Code history

2016
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2021
2022
2023
2024
2025
2026
2027

FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
No changes since FY2016.

Common questions about M66

Is M66 billable?: No. M66 is a header code. Report one of its more specific subcodes instead.