M86.362
BillableChronic multifocal osteomyelitis, left tibia and fibula
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.362 an HCC code?
Yes. M86.362 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 M86.362
For M86.362 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 M86.362 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.362 is the ICD-10-CM diagnosis code for chronic multifocal osteomyelitis, left tibia and fibula. A chronic bone infection affecting multiple areas of the left shin bone and smaller bone next to it, characterized by persistent inflammation and potential drainage. M86.362 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, M86.362 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, M86.362 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 laterality is documented as 'left' in the medical record before assigning this code. Because M86.362 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 M86.362 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify laterality is documented as 'left' in the medical record before assigning this code
- •Confirm the infection is multifocal (multiple sites) and chronic (long-standing) rather than acute
Clinical Significance
This diagnosis captures chronic multifocal osteomyelitis of the left tibia and fibula, a serious condition affecting both bones of the lower leg with significant implications for mobility and function. The multifocal nature indicates extensive disease requiring aggressive treatment and monitoring.
Documentation Requirements
- ✓Clear documentation of left tibia and fibula involvement
- ✓Evidence supporting chronic nature (duration >6 weeks or recurrent)
- ✓Confirmation of multifocal pattern in both bones
- ✓Imaging studies demonstrating chronic osteomyelitic changes
- ✓Functional assessment of left lower extremity
- ✓Laboratory markers consistent with chronic infection
- ✓Treatment history including medical and surgical approaches
- ✓Clinical correlation with chronic multifocal osteomyelitis
Commonly Confused Codes
- •M86.162 — Acute osteomyelitis of left tibia and fibula, acute presentation
- •M86.361 — Same condition but right-sided
- •M86.462 — Chronic osteomyelitis with draining sinus of left tibia/fibula
- •M86.562 — Other chronic hematogenous osteomyelitis, different etiology
- •M79.604 — Pain in left leg, lacks infectious component