M86.439
BillableChronic osteomyelitis with draining sinus, unspecified radius and ulna
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.439 an HCC code?
Yes. M86.439 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 M86.439
For M86.439 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 M86.439 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.439 is the ICD-10-CM diagnosis code for chronic osteomyelitis with draining sinus, unspecified radius and ulna. A long-term bone infection in the forearm bones (radius and ulna) with a draining sinus tract, but the specific side (right or left) is not identified. M86.439 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, M86.439 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, M86.439 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 is a less specific code; attempt to determine laterality from clinical documentation or query the provider. Because M86.439 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 M86.439 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Chronic osteomyelitis with draining sinus of unspecified radius and ulna indicates a severe bone infection affecting forearm bones with persistent drainage when laterality is not documented. This condition significantly impacts arm function and requires intensive management due to drainage complications.
Documentation Requirements
- ✓Documentation of radius and ulna involvement without laterality
- ✓Evidence of chronic infection (>6 weeks duration or recurrent)
- ✓Confirmation of active draining sinus tract from forearm bones
- ✓Imaging findings consistent with chronic osteomyelitis
- ✓Clinical evidence of persistent drainage from forearm
- ✓Laboratory evidence supporting chronic infectious process
- ✓Treatment history addressing both infection and drainage
- ✓Absence of clear laterality specification in record