M86.259
BillableSubacute osteomyelitis, unspecified femur
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.259 an HCC code?
Yes. M86.259 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 M86.259
For M86.259 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 M86.259 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.259 is the ICD-10-CM diagnosis code for subacute osteomyelitis, unspecified femur. A bone infection in the thighbone with unclear or unspecified side that develops gradually over weeks to months. M86.259 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, M86.259 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, M86.259 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.
This is a less specific code; attempt to clarify laterality through provider query when possible. Because M86.259 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 M86.259 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a less specific code; attempt to clarify laterality through provider query when possible
- •Document the clinical presentation and any imaging findings to support the diagnosis
Clinical Significance
Subacute osteomyelitis of unspecified femur represents an intermediate-phase bone infection developing over weeks to months where laterality documentation is unavailable. This condition poses significant risk for progression to chronic infection and functional disability, requiring careful monitoring and prolonged antibiotic therapy to preserve mobility and prevent complications.
Documentation Requirements
- ✓Documentation of subacute osteomyelitis involving femur
- ✓Evidence that laterality is unspecified or unknown
- ✓Clinical timeline consistent with subacute infection (weeks to months)
- ✓Imaging findings supporting femur osteomyelitis
- ✓Laboratory markers indicating ongoing infection
- ✓Culture results and organism identification when possible
- ✓Assessment of weight-bearing capacity and functional status
- ✓Documentation of treatment response and infection progression