Question 1

What is ICD-10 code M66.144?

Accepted Answer

M66.144 is the ICD-10-CM diagnosis code for rupture of synovium, right finger(s). A tear or rupture of the synovium (joint lining) in the right finger(s), causing pain, swelling, and reduced finger mobility. M66.144 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).

M66.144 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 code applies to right finger joints; verify right side is documented.

Question 2

Is M66.144 an HCC code?

Accepted Answer

No. M66.144 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is M66.144 billable?

Accepted Answer

Yes. M66.144 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. M66.144 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Question 4

What is the V28 vs V24 difference for M66.144?

Accepted Answer

M66.144 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither community model rewards M66.144 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's V28/V24 community RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a community payment HCC.

Question 5

What should coders know when reporting M66.144?

Accepted Answer

This code applies to right finger joints; verify right side is documented Document which finger(s) are affected if possible, though this code encompasses all right fingers

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M66.144

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M66.144 ICD-10-CM Code: Rupture of synovium, right finger(s)

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M66.144

Is M66.144 an HCC code?

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