M86.361
BillableChronic multifocal osteomyelitis, right tibia and fibula
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.361 an HCC code?
Yes. M86.361 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 M86.361
For M86.361 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 M86.361 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.361 is the ICD-10-CM diagnosis code for chronic multifocal osteomyelitis, right tibia and fibula. A chronic bone infection affecting multiple areas of the right lower leg bones (tibia and fibula), characterized by persistent inflammation and bone damage. M86.361 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, M86.361 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, M86.361 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 both tibia and fibula involvement or multifocal sites within these bones. Because M86.361 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 M86.361 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify both tibia and fibula involvement or multifocal sites within these bones
- •Confirm right-sided location is documented in the medical record
Clinical Significance
Chronic multifocal osteomyelitis of the right tibia and fibula represents a complex infection of both lower leg bones, significantly impacting weight-bearing and mobility. This condition requires comprehensive treatment due to the bones' critical role in ambulation and high risk for complications.
Documentation Requirements
- ✓Specific documentation of right tibia and fibula involvement
- ✓Evidence of chronicity (>6 weeks duration or recurrent episodes)
- ✓Confirmation of multifocal involvement within both bones
- ✓Radiographic evidence of chronic osteomyelitic changes
- ✓Assessment of weight-bearing capacity and gait function
- ✓Laboratory findings supporting chronic infectious process
- ✓Documentation of treatment approaches and outcomes
- ✓Provider confirmation of chronic multifocal osteomyelitis diagnosis