ICD-10-CM 2027 diagnosis code
M66.9Spontaneous rupture of unspecified tendon
M66.9 is a valid, billable ICD-10-CM code for spontaneous rupture of unspecified tendon. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.
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 M66.9
M66.9 is the ICD-10-CM diagnosis code for spontaneous rupture of unspecified tendon. 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 billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.
Within M66, choose M66.9 (Spontaneous rupture of unspecified tendon) only when documentation doesn't support a more specific option: rupture of popliteal cyst (M66.0), rupture of synovium (M66.1), spontaneous rupture of extensor tendons (M66.2), spontaneous rupture of flexor tendons (M66.3) and spontaneous rupture of other tendons (M66.8).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 557 (Tendonitis, Myositis and Bursitis with MCC, relative weight 1.489) and DRG 558 (Tendonitis, Myositis and Bursitis without MCC, relative weight 0.8875), in MDC 08 (Diseases and Disorders of the Musculoskeletal System and Connective Tissue), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.
Before ICD-10, this condition was coded in ICD-9-CM as 727.60 (nontraumatic rupture of unspecified tendon).
Coding notes
- Rupture at musculotendinous junction, nontraumatic
Notes that apply from higher levels
Instructions written at a parent level also apply to M66.9.
› From M66 Spontaneous rupture of synovium and tendon
- rupture that occurs when a normal force is applied to tissues that are inferred to have less than normal strength
- 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.
Alphabetic index entries
1 entriesTerms in the official ICD-10-CM index that lead to M66.9.
MS-DRG v44.0 grouping
All DRGs →Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.
MDC 08 · Diseases and Disorders of the Musculoskeletal System and Connective Tissue
ICD-9-CM equivalent
Converter →- 727.60Nontraumatic rupture of unspecified tendonapproximate
From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 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 M66.9
Is M66.9 billable?
- Yes. M66.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can M66.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict M66.9 as a principal diagnosis.
Is M66.9 a CC or MCC?
- No. M66.9 is neither a CC nor an MCC under MS-DRG v44.0.
What DRG does M66.9 group to?
- M66.9 is used in the MS-DRG v44.0 logic for MS-DRG 557 (Tendonitis, Myositis and Bursitis with MCC) and MS-DRG 558 (Tendonitis, Myositis and Bursitis without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.
What is the ICD-9 code for M66.9?
- The CMS General Equivalence Mappings map M66.9 to ICD-9-CM 727.60.