M87.266
BillableOsteonecrosis due to previous trauma, unspecified fibula
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.266 an HCC code?
Yes. M87.266 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 M87.266
For M87.266 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 M87.266 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.266 is the ICD-10-CM diagnosis code for osteonecrosis due to previous trauma, unspecified fibula. Death of bone tissue in the smaller bone of the lower leg (fibula) caused by previous trauma, but the specific side (left or right) is not specified or documented. M87.266 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, M87.266 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, M87.266 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 only when laterality cannot be determined from available documentation; attempt to obtain clarification from provider. Because M87.266 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 M87.266 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use only when laterality cannot be determined from available documentation; attempt to obtain clarification from provider
- •This unspecified code is less preferred; strive to code to the most specific laterality when possible
Clinical Significance
Unspecified fibular osteonecrosis following trauma represents bone death in the lateral support structure of the lower leg, which can affect ankle stability and gait mechanics. This condition requires ongoing orthopedic monitoring and may impact overall lower extremity function.
Documentation Requirements
- ✓Documentation of fibula involvement without specified laterality
- ✓Clear history of previous trauma to lower leg area
- ✓Evidence of bone necrosis in fibular structures
- ✓Justification for unspecified laterality (bilateral involvement or unclear documentation)
- ✓Assessment of ankle stability and function
- ✓Current pain levels and mobility status
- ✓Treatment modalities and effectiveness
- ✓Impact on gait and weight-bearing capacity