M90.569
BillableOsteonecrosis in diseases classified elsewhere, unspecified lower leg
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M90.569 an HCC code?
Yes. M90.569 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 M90.569
For M90.569 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 M90.569 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M90.569 is the ICD-10-CM diagnosis code for osteonecrosis in diseases classified elsewhere, unspecified lower leg. Bone death (osteonecrosis) in the lower leg caused by another disease, side not specified. The bone tissue in the lower leg dies as a secondary effect of an underlying condition. M90.569 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, M90.569 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, M90.569 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.
Use only when the specific side of the lower leg is not documented or is bilateral. Because M90.569 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 M90.569 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use only when the specific side of the lower leg is not documented or is bilateral
- •Always pair with a secondary diagnosis code for the underlying disease causing the osteonecrosis
Clinical Significance
Secondary osteonecrosis of unspecified lower leg represents bone death in tibia or fibula caused by an underlying classified disease, requiring complex medical management. This diagnosis significantly impacts risk adjustment modeling due to mobility limitations and the critical role of lower leg bones in weight-bearing function.
Documentation Requirements
- ✓Clear documentation of underlying disease causing secondary osteonecrosis
- ✓Clinical evidence of lower leg bone involvement without laterality specification
- ✓Radiological confirmation of osteonecrotic changes (MRI, bone scan, CT)
- ✓Provider statement establishing causal relationship to classified disease
- ✓Treatment plan addressing both primary condition and bone necrosis
- ✓Assessment of weight-bearing capacity and mobility status
- ✓Documentation excluding primary or traumatic causes
- ✓Monitoring plan for potential complications and treatment response