M86.462
BillableChronic osteomyelitis with draining sinus, left tibia and fibula
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.462 an HCC code?
Yes. M86.462 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 M86.462
For M86.462 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 M86.462 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.462 is the ICD-10-CM diagnosis code for chronic osteomyelitis with draining sinus, left tibia and fibula. A chronic bone infection of the left shin bones (tibia and fibula) that has created an open drainage channel through the skin, allowing infected material to drain continuously. M86.462 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, M86.462 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, M86.462 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 M86.462 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 M86.462 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
- •This code encompasses both the tibia and fibula as a single anatomical unit in the lower leg
Clinical Significance
Chronic osteomyelitis with draining sinus of the left tibia and fibula indicates a severe, persistent bone infection with external drainage pathway that significantly compromises lower extremity function. This complex condition requires intensive antibiotic therapy, surgical intervention, and ongoing wound management, substantially impacting patient mobility and overall health status.
Documentation Requirements
- ✓Documentation of chronic osteomyelitis with established diagnosis
- ✓Clear evidence of draining sinus tract presence and activity
- ✓Anatomic specification of left tibia and fibula involvement
- ✓Detailed description of drainage characteristics and volume
- ✓Culture results and antibiotic sensitivity testing
- ✓Imaging studies confirming infection extent and sinus tract
- ✓Treatment regimen including antibiotic duration and surgical history
- ✓Functional assessment and impact on daily activities
Commonly Confused Codes
- •M86.461 — Chronic osteomyelitis with draining sinus, right tibia and fibula (incorrect laterality)
- •M86.662 — Other chronic osteomyelitis, left tibia and fibula (lacks draining sinus)
- •M86.562 — Other chronic hematogenous osteomyelitis, left tibia and fibula (different etiology)
- •M86.472 — Chronic osteomyelitis with draining sinus, left ankle and foot (different anatomy)