M86.561
BillableOther chronic hematogenous 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 M86.561 an HCC code?
Yes. M86.561 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 M86.561
For M86.561 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 M86.561 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.561 is the ICD-10-CM diagnosis code for other chronic hematogenous osteomyelitis, right tibia and fibula. A chronic bone infection of the right shinbone and smaller leg bone (tibia and fibula) that developed from bacteria spreading through the bloodstream. M86.561 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, M86.561 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, M86.561 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.
This code covers both the tibia and fibula on the right side; do not assign separate codes for each bone. Because M86.561 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 M86.561 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code covers both the tibia and fibula on the right side; do not assign separate codes for each bone
- •Confirm right leg is documented to avoid miscoding as left or unspecified
Clinical Significance
Chronic hematogenous osteomyelitis affecting the right tibia and fibula represents a complex bone infection involving the primary weight-bearing bones of the lower leg. This condition significantly impacts mobility and may lead to long-term disability, requiring coordinated medical and surgical management.
Documentation Requirements
- ✓Documentation of chronic nature (>6 weeks duration or recurrent)
- ✓Evidence of hematogenous origin (bloodstream spread)
- ✓Specific involvement of right tibia and/or fibula
- ✓Imaging studies showing bone infection (plain films, MRI, bone scan)
- ✓Laboratory evidence of infection (ESR, CRP, cultures)
- ✓Assessment of lower extremity function and weight-bearing ability
- ✓Documentation of treatment regimen and surgical interventions
- ✓Evaluation for complications such as fractures or deformity
Commonly Confused Codes
- •M86.562 — Other chronic hematogenous osteomyelitis, left tibia and fibula (opposite side)
- •M86.661 — Other chronic osteomyelitis, right tibia and fibula (non-hematogenous)
- •M86.461 — Chronic osteomyelitis with draining sinus, right tibia and fibula (has sinus)
- •M86.161 — Other acute osteomyelitis, right tibia and fibula (acute phase)
- •S82.90XA — Unspecified fracture of right lower leg (trauma-related)