M86.39
BillableChronic multifocal osteomyelitis, multiple sites
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.39 an HCC code?
Yes. M86.39 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 M86.39
For M86.39 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 M86.39 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.39 is the ICD-10-CM diagnosis code for chronic multifocal osteomyelitis, multiple sites. A chronic bone infection affecting multiple areas throughout the body in more than one anatomical region. M86.39 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, M86.39 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, M86.39 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 code indicates involvement of multiple sites across different body regions. Because M86.39 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 M86.39 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code indicates involvement of multiple sites across different body regions
- •Document all affected sites and consider using additional codes if specific regions are clearly identified
Clinical Significance
Chronic multifocal osteomyelitis affecting multiple sites represents the most severe form of this condition, with infection involving bones across different anatomical regions simultaneously. This diagnosis indicates extensive disease requiring comprehensive, multidisciplinary management with significant morbidity risk.
Documentation Requirements
- ✓Documentation of involvement in multiple distinct anatomical sites
- ✓Evidence of chronicity across all affected sites (>6 weeks or recurrent)
- ✓Confirmation of multifocal pattern within multiple bone regions
- ✓Imaging studies showing chronic changes at multiple locations
- ✓Comprehensive assessment of functional impact across body regions
- ✓Laboratory markers consistent with systemic chronic infection
- ✓Treatment documentation addressing multiple site complexity
- ✓Provider assessment confirming extensive multifocal osteomyelitis