M86.371
BillableChronic multifocal osteomyelitis, right ankle and foot
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.371 an HCC code?
Yes. M86.371 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 M86.371
For M86.371 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 M86.371 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.371 is the ICD-10-CM diagnosis code for chronic multifocal osteomyelitis, right ankle and foot. A chronic bone infection affecting multiple areas of the right ankle and foot bones, often resulting in persistent pain and potential drainage. M86.371 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, M86.371 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, M86.371 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.
Ensure documentation specifies 'right' ankle and foot involvement. Because M86.371 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 M86.371 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure documentation specifies 'right' ankle and foot involvement
- •Distinguish between multifocal osteomyelitis and monostotic (single site) infection
Clinical Significance
Chronic multifocal osteomyelitis of the right ankle and foot represents a complex infection affecting multiple bones in the weight-bearing extremity, significantly impacting mobility and quality of life. This condition poses high risk for functional disability and may require extensive reconstruction.
Documentation Requirements
- ✓Specific documentation of right ankle and foot involvement
- ✓Evidence of chronicity (>6 weeks duration or recurrent episodes)
- ✓Confirmation of multifocal pattern in ankle/foot bones
- ✓Imaging findings demonstrating chronic osteomyelitic changes
- ✓Assessment of weight-bearing capacity and gait
- ✓Laboratory findings supporting chronic infectious process
- ✓Documentation of treatment modalities and responses
- ✓Provider assessment confirming chronic multifocal osteomyelitis