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ICD-10-CM 2027 diagnosis code

M66.3Spontaneous rupture of flexor tendons

Not billable — use a more specific code

M66.3 is a header code, so it can't be reported by itself. Choose one of the 10 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 M66.3

M66.3 is the ICD-10-CM diagnosis code for spontaneous rupture of flexor tendons. It belongs to category M66 (spontaneous rupture of synovium and tendon), 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 10 subcodes must be used instead.

Within M66 (spontaneous rupture of synovium and tendon), M66.3 is specifically for spontaneous rupture of flexor tendons. Related codes cover rupture of popliteal cyst (M66.0), rupture of synovium (M66.1), spontaneous rupture of extensor tendons (M66.2), spontaneous rupture of other tendons (M66.8) and spontaneous rupture of unspecified tendon (M66.9).

To report this condition, pick the subcode that matches the documentation: M66.30 (unspecified site), M66.31 (shoulder), M66.32 (upper arm), M66.33 (forearm), M66.34 (hand), M66.35 (thigh), M66.36 (lower leg), M66.37 (ankle and foot) and 2 more.

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 M66.3

Notes that apply from higher levels

Instructions written at a parent level also apply to M66.3.

› From M66 Spontaneous rupture of synovium and tendon
Includes
  • rupture that occurs when a normal force is applied to tissues that are inferred to have less than normal strength
Excludes2
  • rotator cuff syndrome (M75.1-)
  • rupture where an abnormal force is applied to normal tissue - see injury of tendon by body region

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

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about M66.3

Is M66.3 billable?

No. M66.3 is a header code. Report one of its more specific subcodes instead.