Question 1

What is ICD-10 code M23.229?

Accepted Answer

M23.229 is the ICD-10-CM diagnosis code for derangement of posterior horn of medial meniscus due to old tear or injury, unspecified knee. Damage to the back part of the inner knee cartilage (meniscus) from an old tear or injury with the knee side not specified. M23.229 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering other joint disorders (m20-m25).

M23.229 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 specific knee (right or left) is not documented or is bilateral.

Question 2

Is M23.229 an HCC code?

Accepted Answer

No. M23.229 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 M23.229 billable?

Accepted Answer

Yes. M23.229 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. M23.229 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 M23.229?

Accepted Answer

M23.229 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 M23.229 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 M23.229?

Accepted Answer

Use this code only when the specific knee (right or left) is not documented or is bilateral Query the provider if laterality can be determined from clinical notes or imaging reports

M23.229

Is M23.229 an HCC code?

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Open M23.229 in the Interactive Encoder