M87.865
BillableOther osteonecrosis, left fibula
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.865 an HCC code?
Yes. M87.865 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 M87.865
For M87.865to 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 M87.865 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.865 is the ICD-10-CM diagnosis code for other osteonecrosis, left fibula. Death of bone tissue in the left fibula (smaller bone in the lower leg) due to causes other than trauma or radiation. M87.865 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, M87.865 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, M87.865 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 left side documentation in the medical record. Because M87.865 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 M87.865 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify left side documentation in the medical record
- •Note that fibula osteonecrosis is less common than tibia involvement but requires specific coding
Clinical Significance
Left fibular osteonecrosis indicates avascular death of bone tissue in the smaller bone of the lower leg, potentially compromising ankle function and weight distribution. This condition requires ongoing orthopedic management to maintain limb stability and function.
Documentation Requirements
- ✓Clear documentation of left fibula involvement
- ✓Imaging studies demonstrating osteonecrosis (MRI most sensitive)
- ✓Exclusion of traumatic, infectious, or radiation-induced etiology
- ✓Assessment of ankle joint stability and function
- ✓Pain scale documentation and mobility impact
- ✓Evaluation for underlying predisposing conditions
- ✓Conservative vs surgical treatment considerations
- ✓Long-term monitoring plan for disease progression
Commonly Confused Codes
- •M87.365 — Drug-induced osteonecrosis requires identification of causative agent
- •M87.165 — Post-traumatic osteonecrosis needs trauma documentation
- •M87.065 — Idiopathic osteonecrosis has no identifiable underlying cause
- •S82.401A — Acute fibular fracture is injury-related, not avascular necrosis
- •M86.662 — Chronic osteomyelitis involves bacterial infection of bone