M86.471
BillableChronic osteomyelitis with draining sinus, right ankle and foot
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.471 an HCC code?
Yes. M86.471 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 M86.471
For M86.471 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 M86.471 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.471 is the ICD-10-CM diagnosis code for chronic osteomyelitis with draining sinus, right ankle and foot. A chronic bone infection of the right ankle and foot bones that has created an open drainage channel through the skin, allowing infected material to drain continuously. M86.471 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, M86.471 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, M86.471 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 'right' in the medical record before assigning this code. Because M86.471 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 M86.471 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 'right' in the medical record before assigning this code
- •This code applies to chronic osteomyelitis affecting any bones in the right ankle and foot region
Clinical Significance
Chronic osteomyelitis with draining sinus of the right ankle and foot represents a severe, complicated bone infection with persistent drainage that significantly impacts mobility and weight-bearing function. This condition requires intensive treatment including prolonged antibiotics, surgical debridement, and specialized wound care, substantially affecting patient quality of life and functional capacity.
Documentation Requirements
- ✓Documentation of chronic osteomyelitis diagnosis
- ✓Clear evidence of draining sinus tract with ongoing drainage
- ✓Specific identification of right ankle and foot involvement
- ✓Detailed description of sinus tract location and drainage
- ✓Microbiological studies and culture results
- ✓Imaging studies demonstrating infection and sinus pathway
- ✓Treatment history including antibiotic therapy and surgical interventions
- ✓Assessment of ambulation status and functional limitations