M90.529
BillableOsteonecrosis in diseases classified elsewhere, unspecified upper arm
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M90.529 an HCC code?
Yes. M90.529 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 M90.529
For M90.529 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 M90.529 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M90.529 is the ICD-10-CM diagnosis code for osteonecrosis in diseases classified elsewhere, unspecified upper arm. Death of bone tissue in the upper arm (side not specified) caused by another disease or condition affecting the body. M90.529 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, M90.529 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, M90.529 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 this code only when laterality (left or right) cannot be determined from documentation. Because M90.529 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 M90.529 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when laterality (left or right) cannot be determined from documentation
- •Always pair with the underlying disease code that is causing the osteonecrosis
Clinical Significance
Secondary osteonecrosis of the upper arm without laterality specification represents bone death in the humerus caused by underlying systemic disease. This condition indicates serious skeletal complications with potential for pathological fracture and functional impairment requiring comprehensive management.
Documentation Requirements
- ✓Primary causative disease documented and coded first per coding guidelines
- ✓Clinical evidence of upper arm bone necrosis present
- ✓Diagnostic imaging studies confirming osteonecrosis
- ✓Functional assessment of affected upper extremity
- ✓Risk stratification for potential pathological fracture
- ✓Treatment plan addressing both underlying disease and bone pathology
- ✓Documentation explaining why laterality cannot be specified