M66.146 ICD-10-CM Code: Rupture of synovium, unspecified finger(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)
M66.146
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceRupture of synovium, unspecified finger(s)
A tear or rupture of the synovium (the lining inside a joint) affecting one or more fingers, when the specific finger 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 M66.146 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M66.146 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M66.146 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M66.146 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M66.146 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M66.146 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M66.146 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 M66.146 an HCC code?
No. M66.146 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
M66.146 is the ICD-10-CM diagnosis code for rupture of synovium, unspecified finger(s). A tear or rupture of the synovium (the lining inside a joint) affecting one or more fingers, when the specific finger is not documented. M66.146 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).
M66.146 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 the documentation does not specify which finger(s) are affected; if specific fingers are identified, use more specific codes.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M66.146 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 the documentation does not specify which finger(s) are affected; if specific fingers are identified, use more specific codes
- •Synovial rupture often results from trauma or underlying joint disease; review clinical notes for causative factors