M86.261
BillableSubacute osteomyelitis, right tibia and fibula
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.261 an HCC code?
Yes. M86.261 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 M86.261
For M86.261 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 M86.261 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.261 is the ICD-10-CM diagnosis code for subacute osteomyelitis, right tibia and fibula. A bone infection in the right shin bone and smaller bone of the lower leg that develops gradually over weeks to months. M86.261 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, M86.261 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, M86.261 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.
Confirm documentation specifies right tibia and fibula involvement. Because M86.261 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 M86.261 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm documentation specifies right tibia and fibula involvement
- •Note whether infection affects one or both bones in the lower leg
Clinical Significance
Subacute osteomyelitis of the right tibia and fibula represents an intermediate-stage bone infection that develops gradually over weeks to months, significantly impacting lower extremity function and ambulation. This dual-bone involvement increases treatment complexity and risk of complications including growth disturbances, chronic infection, and permanent disability.
Documentation Requirements
- ✓Clear documentation of subacute osteomyelitis
- ✓Specific identification of right tibia and fibula involvement
- ✓Evidence of infection timeline spanning weeks to months
- ✓Clinical presentation consistent with lower leg bone infection
- ✓Imaging confirmation of osteomyelitis in tibia and/or fibula
- ✓Laboratory findings supporting ongoing infectious process
- ✓Culture results and antibiotic sensitivity testing
- ✓Assessment of weight-bearing ability and gait disturbances