M90.58
BillableOsteonecrosis in diseases classified elsewhere, other site
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M90.58 an HCC code?
Yes. M90.58 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 M90.58
For M90.58 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 M90.58 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M90.58 is the ICD-10-CM diagnosis code for osteonecrosis in diseases classified elsewhere, other site. Bone death (osteonecrosis) in other bone locations caused by another disease. The bone tissue dies as a secondary effect of an underlying condition in sites not covered by other specific codes. M90.58 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, M90.58 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, M90.58 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 for osteonecrosis in unusual or multiple specific sites not captured by other M90.5x codes. Because M90.58 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 M90.58 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code for osteonecrosis in unusual or multiple specific sites not captured by other M90.5x codes
- •Requires a secondary diagnosis code for the underlying disease causing the osteonecrosis
Clinical Significance
Secondary osteonecrosis at other anatomical sites represents bone death caused by an underlying classified disease affecting locations not covered by specific codes. This diagnosis requires specialized medical management and impacts risk adjustment modeling due to the complex nature of systemic disease-related bone necrosis.
Documentation Requirements
- ✓Clear documentation of underlying classified disease causing the osteonecrosis
- ✓Specific identification of anatomical site not covered by other M905 codes
- ✓Radiological evidence of bone necrosis (MRI, bone scan, or CT imaging)
- ✓Clinical correlation between primary disease and secondary bone death
- ✓Treatment plan addressing both underlying condition and osteonecrosis
- ✓Assessment of functional impact specific to the affected site
- ✓Provider statement confirming secondary rather than primary cause
- ✓Documentation excluding sites covered by other specific codes
Commonly Confused Codes
- •M87.08 — Primary osteonecrosis of other site, not secondary to disease
- •M90.59 — Same condition affecting multiple sites rather than single other site
- •M86.18 — Chronic osteomyelitis of other site involving infection rather than necrosis
- •M89.08 — Other specified disorders of bone affecting other sites
- •M85.80 — Other specified disorders of bone density affecting other sites