M86.571
BillableOther chronic hematogenous osteomyelitis, right ankle and foot
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.571 an HCC code?
Yes. M86.571 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 M86.571
For M86.571 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 M86.571 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.571 is the ICD-10-CM diagnosis code for other chronic hematogenous osteomyelitis, right ankle and foot. A long-term bone infection in the right ankle or foot that started from bacteria spreading through the bloodstream. M86.571 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, M86.571 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, M86.571 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 M86.571 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 M86.571 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
- •Confirm the infection is chronic (ongoing) and hematogenous (blood-borne) in origin
Clinical Significance
Chronic hematogenous osteomyelitis of the right ankle and foot represents a complex infection affecting multiple small bones critical for weight-bearing and ambulation. This condition significantly impacts mobility and balance, often requiring specialized orthopedic management and potentially leading to long-term disability.
Documentation Requirements
- ✓Documentation of chronic duration (>6 weeks or recurrent episodes)
- ✓Evidence of hematogenous spread (bloodstream origin)
- ✓Specific involvement of right ankle and/or foot bones
- ✓Imaging studies demonstrating bone infection (X-ray, MRI, bone scan)
- ✓Laboratory confirmation of infection (ESR, CRP, cultures)
- ✓Assessment of weight-bearing capacity and gait
- ✓Documentation of treatment including antibiotics and surgical interventions
- ✓Evaluation of functional limitations and mobility aids needed