M86.461
BillableChronic osteomyelitis with draining sinus, right tibia and fibula
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.461 an HCC code?
Yes. M86.461 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 M86.461
For M86.461 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 M86.461 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.461 is the ICD-10-CM diagnosis code for chronic osteomyelitis with draining sinus, right tibia and fibula. A chronic bone infection of the right shin bones (tibia and fibula) that has created an open drainage channel through the skin, allowing infected material to drain continuously. M86.461 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, M86.461 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, M86.461 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 M86.461 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 M86.461 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 encompasses both the tibia and fibula as a single anatomical unit in the lower leg
Clinical Significance
Chronic osteomyelitis with draining sinus affecting the right tibia and fibula represents a complex, long-standing bone infection with persistent external drainage requiring intensive medical and surgical management. The involvement of both lower leg bones significantly impacts mobility and weight-bearing capacity, necessitating comprehensive treatment approaches and long-term monitoring.
Documentation Requirements
- ✓Clear documentation of chronic osteomyelitis diagnosis
- ✓Evidence of draining sinus tract with ongoing drainage
- ✓Specific identification of right tibia and fibula involvement
- ✓Description of sinus tract location and characteristics
- ✓Microbiological identification from cultures
- ✓Imaging studies showing bone infection and sinus pathway
- ✓Comprehensive treatment history and current management
- ✓Assessment of functional impact on ambulation and weight-bearing
Commonly Confused Codes
- •M86.462 — Chronic osteomyelitis with draining sinus, left tibia and fibula (wrong laterality)
- •M86.661 — Other chronic osteomyelitis, right tibia and fibula (no draining sinus)
- •M86.561 — Other chronic hematogenous osteomyelitis, right tibia and fibula (different type)
- •M86.441 — Chronic osteomyelitis with draining sinus, right femur (wrong bone)