M90.571
BillableOsteonecrosis in diseases classified elsewhere, right ankle and foot
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M90.571 an HCC code?
Yes. M90.571 maps to Bone/Joint/Muscle Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for M90.571
For M90.571 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed M90.571 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M90.571 is the ICD-10-CM diagnosis code for osteonecrosis in diseases classified elsewhere, right ankle and foot. Bone death (osteonecrosis) in the right ankle and foot caused by another disease. The bone tissue in the ankle and foot dies as a secondary effect of an underlying condition. M90.571 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).
Under the CMS-HCC V28 risk adjustment model, M90.571 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.209. Under the older V24 model, M90.571 mapped to the same category but with a base RAF weight of 0.482 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Requires a secondary diagnosis code for the underlying disease causing the osteonecrosis. Because M90.571 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M90.571 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Requires a secondary diagnosis code for the underlying disease causing the osteonecrosis
- •Laterality is specified as right; covers both ankle and foot structures on the right side
Clinical Significance
Secondary osteonecrosis of right ankle and foot represents bone death in these critical weight-bearing structures caused by an underlying classified disease. This diagnosis requires specialized medical management and significantly impacts risk adjustment due to mobility limitations and complex care needs.
Documentation Requirements
- ✓Documentation of underlying classified disease causing the osteonecrosis
- ✓Specific identification of right ankle and/or foot bone involvement
- ✓Imaging evidence of bone necrosis (MRI, bone scan, or CT studies)
- ✓Clinical correlation between primary disease and secondary bone death
- ✓Current treatment modalities for both conditions
- ✓Assessment of weight-bearing ability and ambulatory status
- ✓Provider documentation confirming secondary rather than primary cause
- ✓Monitoring for complications including fracture risk and healing status