Question 1

What is ICD-10 code M89.021?

Accepted Answer

M89.021 is the ICD-10-CM diagnosis code for algoneurodystrophy, right upper arm. Complex regional pain syndrome affecting the right upper arm, causing pain, swelling, and functional impairment in that arm. M89.021 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering other osteopathies (m86-m90).

M89.021 is a billable ICD-10-CM code, but the current payload does not show a mapping under the CMS-HCC V28, V24, ESRD, or RxHCC models. Do not assign risk adjustment value from this page when no source-backed mapping is shown; verify the applicable model and payment year.

Upper arm refers to the area between shoulder and elbow; ensure documentation specifies right side.

Question 2

Is M89.021 an HCC code?

Accepted Answer

No. M89.021 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 M89.021 billable?

Accepted Answer

Yes. M89.021 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. M89.021 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

Which HCC does M89.021 map to under V28?

Accepted Answer

M89.021 does not map to a CMS-HCC V28 payment category. Check the current CMS-HCC V28 model file for payment year 2026 rather than an older V24 tip sheet.

Question 5

What RAF reference is published for M89.021?

Accepted Answer

M89.021 has no separately stated V28 community reference coefficient. Check the current CMS mapping and factor files before using it in any member-score workflow.

Question 6

What is the V28 vs V24 difference for M89.021?

Accepted Answer

M89.021 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 M89.021 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 7

What documentation supports M89.021?

Accepted Answer

Upper arm refers to the area between shoulder and elbow; ensure documentation specifies right side Distinguish from shoulder (M89.01) and forearm codes when determining the exact anatomical location M89.021 is not a CMS-HCC payment code, so MEAT is not the payment hook. Documentation still has to support the diagnosis if you report it.

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M89.021

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M89.021 ICD-10-CM Code: Algoneurodystrophy, right upper arm

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M89.021

Is M89.021 an HCC code?

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What This Code Means

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Child Codes

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Work M89.021 in HCC Buddy