M66.9 ICD-10-CM Code: Spontaneous rupture of unspecified tendon
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Disorders of synovium and tendon (M65-M67)
M66.9
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceSpontaneous rupture of unspecified tendon
A spontaneous tear or rupture of a tendon when the specific tendon involved cannot be identified or is not documented.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
00
RAF 0
ACA/HHS
00
RAF 0
ESRD/PACE
00
RAF 0
RXHCC
00
RAF 0
Code Trumping
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Code Book Path
Inclusion Terms
Official- Rupture at musculotendinous junction, nontraumatic
Excludes 2
Official- rotator cuff syndrome (M75.1-)
- rupture where an abnormal force is applied to normal tissue - see injury of tendon by body region
Related Child Codes
Includes
Official- rupture that occurs when a normal force is applied to tissues that are inferred to have less than normal strength
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M66.9 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M66.9 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M66.9 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M66.9 in this effective period.
Buddy Documentation Tip
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is M66.9 an HCC code?
No. M66.9 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
Coder workflow notes
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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
M66.9 is the ICD-10-CM diagnosis code for spontaneous rupture of unspecified tendon. A spontaneous tear or rupture of a tendon when the specific tendon involved cannot be identified or is not documented. M66.9 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering disorders of synovium and tendon (m65-m67).
M66.9 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
This is a non-specific code; query the provider for more detail about which tendon ruptured.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M66.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a non-specific code; query the provider for more detail about which tendon ruptured
- •Use only when documentation does not allow for a more specific tendon rupture code