M90.522
BillableOsteonecrosis in diseases classified elsewhere, left upper arm
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M90.522 an HCC code?
Yes. M90.522 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 M90.522
For M90.522 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 M90.522 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M90.522 is the ICD-10-CM diagnosis code for osteonecrosis in diseases classified elsewhere, left upper arm. Death of bone tissue in the left upper arm caused by another disease or condition affecting the body. M90.522 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, M90.522 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, M90.522 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 is a manifestation code - always code the underlying disease first (the condition causing the osteonecrosis). Because M90.522 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 M90.522 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a manifestation code - always code the underlying disease first (the condition causing the osteonecrosis)
- •Verify laterality is documented as left; if not specified, use M90.529 instead
Clinical Significance
Secondary osteonecrosis of the left upper arm indicates bone death in the humerus resulting from underlying systemic disease, creating risk for pathological fracture and significant functional impairment. This diagnosis requires comprehensive management addressing both the primary condition and skeletal complications.
Documentation Requirements
- ✓Underlying disease causing osteonecrosis clearly documented and coded first
- ✓Left upper arm/humerus specifically identified as the affected anatomical site
- ✓Clinical evidence of bone tissue necrosis documented
- ✓Diagnostic imaging confirming presence of osteonecrosis
- ✓Assessment of left arm function and fracture risk
- ✓Treatment plan for both primary disease and bone complications
- ✓Documentation of disease staging or progression
Commonly Confused Codes
- •M87.022 — Idiopathic aseptic necrosis of left humerus (primary, not secondary)
- •M90.521 — Osteonecrosis in diseases classified elsewhere, right upper arm (incorrect laterality)
- •M90.529 — Osteonecrosis in diseases classified elsewhere, unspecified upper arm (lacks specificity)
- •M84.422 — Pathological fracture, left humerus (fracture rather than underlying necrosis)