M86.169
BillableOther acute osteomyelitis, unspecified tibia and fibula
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.169 an HCC code?
Yes. M86.169 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 M86.169
For M86.169 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 M86.169 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.169 is the ICD-10-CM diagnosis code for other acute osteomyelitis, unspecified tibia and fibula. A rapidly developing bone infection in the shinbone and smaller leg bone, but the specific side is not documented. M86.169 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, M86.169 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, M86.169 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.
Query provider for laterality documentation to assign a more specific code if possible. Because M86.169 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 M86.169 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Query provider for laterality documentation to assign a more specific code if possible
- •Use this code only when laterality cannot be determined from available documentation
Clinical Significance
Acute osteomyelitis of unspecified tibia and fibula represents incomplete documentation of a complex dual-bone infection affecting weight-bearing bones. The involvement of both lower leg bones indicates significant tissue involvement requiring comprehensive treatment, but lacks laterality specification.
Documentation Requirements
- ✓Documentation of tibia and fibula involvement without laterality
- ✓Evidence of acute infection in lower leg bones
- ✓Clinical presentation of dual bone infection
- ✓Imaging showing both bone involvement
- ✓Laboratory markers of active infection
- ✓Provider query for laterality specification
- ✓Assessment of weight-bearing impact
- ✓Treatment plan for complex bone infection