M87.059
BillableIdiopathic aseptic necrosis of unspecified femur
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.059 an HCC code?
Yes. M87.059 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 M87.059
For M87.059 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 M87.059 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.059 is the ICD-10-CM diagnosis code for idiopathic aseptic necrosis of unspecified femur. Death of bone tissue in the thighbone (femur) without infection, occurring without a known cause, when the specific side is not specified. This condition commonly affects the femoral head and can severely limit walking and weight-bearing activities. M87.059 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, M87.059 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, M87.059 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 only when laterality cannot be determined from documentation. Because M87.059 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 M87.059 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when laterality cannot be determined from documentation
- •Query the provider to clarify whether the condition is unilateral or bilateral
Clinical Significance
Idiopathic aseptic necrosis of unspecified femur represents bone death in the thighbone when laterality is not documented, commonly affecting the femoral head and severely limiting walking and weight-bearing activities. This condition commonly affects the femoral head and can severely limit walking and weight-bearing activities, often requiring hip replacement surgery.
Documentation Requirements
- ✓Documentation of aseptic necrosis affecting femur bone
- ✓Confirmation of idiopathic etiology without identifiable cause
- ✓Imaging studies showing bone necrosis in femoral structures
- ✓Absence of specific laterality documentation in medical record
- ✓Exclusion of infectious causes through clinical assessment
- ✓Hip and leg functional assessment including weight-bearing ability
- ✓Treatment plan documentation including therapeutic interventions
- ✓Pain management strategies and mobility impact assessment