M86.239
BillableSubacute osteomyelitis, unspecified radius and ulna
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.239 an HCC code?
Yes. M86.239 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 M86.239
For M86.239 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 M86.239 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.239 is the ICD-10-CM diagnosis code for subacute osteomyelitis, unspecified radius and ulna. A bone infection in the forearm bones (radius and ulna) of unspecified side that develops gradually over weeks to months, causing inflammation and potential bone damage. M86.239 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, M86.239 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, M86.239 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 should be used only when laterality cannot be determined; attempt to clarify with provider documentation. Because M86.239 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 M86.239 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code should be used only when laterality cannot be determined; attempt to clarify with provider documentation
- •Document which forearm bone(s) are involved if possible for clinical clarity
Clinical Significance
Subacute osteomyelitis of unspecified radius and ulna represents a complex dual-bone forearm infection with intermediate timeline but lacking laterality specification. This diagnosis requires provider queries for laterality and comprehensive treatment to prevent chronic progression and preserve forearm function.
Documentation Requirements
- ✓Documentation of radius and ulna involvement without laterality
- ✓Evidence of subacute infection timeline
- ✓Clinical presentation of dual forearm bone infection
- ✓Imaging showing both radius and ulna involvement
- ✓Laboratory support for ongoing infection
- ✓Provider query for laterality specification
- ✓Assessment of forearm rotation and function
- ✓Treatment plan for complex dual bone infection