M87.065
BillableIdiopathic aseptic necrosis of left fibula
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.065 an HCC code?
Yes. M87.065 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 M87.065
For M87.065 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 M87.065 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.065 is the ICD-10-CM diagnosis code for idiopathic aseptic necrosis of left fibula. Death of bone tissue in the left fibula (smaller bone in the lower leg) without infection, occurring without a known cause. M87.065 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, M87.065 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, M87.065 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.
Verify laterality is documented as 'left' in the medical record before assigning this code. Because M87.065 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 M87.065 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify laterality is documented as 'left' in the medical record before assigning this code
- •Ensure the necrosis is idiopathic (no trauma, radiation, or other identifiable cause) to distinguish from other M87 subcategories
Clinical Significance
Idiopathic aseptic necrosis of the left fibula represents bone death without infection in the smaller bone of the lower leg, occurring without identifiable cause. This condition can compromise lower leg stability and weight-bearing capacity, potentially requiring surgical intervention and carrying risk for pathological fracture and functional impairment.
Documentation Requirements
- ✓Clear documentation of aseptic necrosis diagnosis
- ✓Specification of left fibula involvement
- ✓Evidence supporting idiopathic (unknown) etiology
- ✓Imaging studies confirming bone necrosis without infection
- ✓Exclusion of traumatic, vascular, or medication-related causes
- ✓Assessment of lower leg stability and function
- ✓Documentation ruling out infectious osteomyelitis
- ✓Treatment plan addressing bone death and functional preservation