M87.079
BillableIdiopathic aseptic necrosis of unspecified toe(s)
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.079 an HCC code?
Yes. M87.079 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 M87.079
For M87.079 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 M87.079 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.079 is the ICD-10-CM diagnosis code for idiopathic aseptic necrosis of unspecified toe(s). Death of bone tissue in one or more toes without infection, occurring without a known cause. M87.079 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, M87.079 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, M87.079 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.
Specify laterality when possible; use M87.071 or M87.072 if side is documented. Because M87.079 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 M87.079 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Idiopathic aseptic necrosis of unspecified toe(s) represents bone death without infection or identifiable cause when laterality is not documented, indicating need for further diagnostic specification. This condition requires ongoing monitoring for potential complications and may necessitate surgical intervention if conservative management fails.
Documentation Requirements
- ✓Documentation of toe involvement without laterality specification
- ✓Confirmation of aseptic nature (no infection present)
- ✓Clear documentation that cause is idiopathic/unknown
- ✓Imaging studies demonstrating osteonecrosis
- ✓Clinical findings supporting the diagnosis
- ✓Exclusion of drug-related or traumatic causes
- ✓Assessment of functional impact
- ✓Evidence that laterality determination was not possible
Commonly Confused Codes
- •M87.077 — Right toe(s) osteonecrosis (use when laterality documented)
- •M87.078 — Left toe(s) osteonecrosis (use when laterality documented)
- •M87.179 — Drug-induced osteonecrosis of unspecified toe(s) (requires medication cause)
- •M87.279 — Trauma-related osteonecrosis of unspecified toe(s) (requires injury history)
- •M86.9 — Osteomyelitis unspecified (infectious process)