Question 1

What is ICD-10 code Z96.661?

Accepted Answer

Z96.661 is the ICD-10-CM diagnosis code for Presence of right artificial ankle joint. A patient has an artificial ankle joint implanted on the right side of their body. This is a prosthetic replacement used when the natural ankle joint is damaged or diseased. Z96.661 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. Z96.661 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Question 2

Is Z96.661 an HCC code?

Accepted Answer

No. Z96.661 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 Z96.661 billable?

Accepted Answer

Yes. Z96.661 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. Z96.661 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 Z96.661?

Accepted Answer

Z96.661 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 model rewards Z96.661 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

Question 5

What should coders know when reporting Z96.661?

Accepted Answer

Use this code only when documenting a right-sided artificial ankle joint; verify laterality in the medical record This is a status code (Z96 category) used to indicate the presence of an implant, not a diagnosis of disease

Z96.661

Is Z96.661 an HCC code?

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