M66.179 ICD-10-CM Code: Rupture of synovium, unspecified toe(s)
HCC Buddy Code Card
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Disorders of synovium and tendon (M65-M67)
M66.179
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceRupture of synovium, unspecified toe(s)
The tissue lining around the joints in one or more toe(s) has ruptured or torn, but the specific side (left or right) is not documented.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
N/A—
Not mapped
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for M66.179 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M66.179 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M66.179 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M66.179 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M66.179 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M66.179 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M66.179 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 M66.179 an HCC code?
No. M66.179 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
M66.179 is the ICD-10-CM diagnosis code for rupture of synovium, unspecified toe(s). The tissue lining around the joints in one or more toe(s) has ruptured or torn, but the specific side (left or right) is not documented. M66.179 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).
M66.179 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.
Use this code only when laterality cannot be determined from documentation.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M66.179 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when laterality cannot be determined from documentation
- •Query the provider if possible to determine whether the rupture is on the right or left side