M90.50
BillableOsteonecrosis in diseases classified elsewhere, unspecified site
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M90.50 an HCC code?
Yes. M90.50 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 M90.50
For M90.50 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 M90.50 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M90.50 is the ICD-10-CM diagnosis code for osteonecrosis in diseases classified elsewhere, unspecified site. Death of bone tissue (osteonecrosis) caused by another disease, affecting an unspecified body location. M90.50 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, M90.50 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, M90.50 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.
This code requires documentation of the underlying disease causing the osteonecrosis; code that condition separately. Because M90.50 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 M90.50 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code requires documentation of the underlying disease causing the osteonecrosis; code that condition separately
- •Query provider for specific anatomical site if not documented, as more specific M90.5 codes exist
Clinical Significance
Secondary osteonecrosis represents bone death caused by underlying disease processes, requiring identification and treatment of both the bone necrosis and causative condition. This diagnosis indicates serious skeletal complications with significant impact on morbidity and healthcare resource utilization.
Documentation Requirements
- ✓Primary disease causing osteonecrosis clearly documented
- ✓Clinical evidence of bone tissue death or necrosis
- ✓Imaging studies confirming osteonecrosis
- ✓Code first the underlying disease process
- ✓Functional assessment of affected area
- ✓Treatment plan addressing both primary disease and bone necrosis
- ✓Staging or severity of osteonecrosis if applicable
Commonly Confused Codes
- •M87.9 — Osteonecrosis, unspecified (primary osteonecrosis, not secondary)
- •M90.5XX — Osteonecrosis in diseases classified elsewhere with specified site (when location is known)
- •M86.9 — Osteomyelitis, unspecified (infection-related bone disease)
- •M84.40 — Pathological fracture, unspecified site (fracture rather than necrosis)