M86.339
BillableChronic multifocal 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 M86.339 an HCC code?
Yes. M86.339 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 M86.339
For M86.339 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 M86.339 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.339 is the ICD-10-CM diagnosis code for chronic multifocal osteomyelitis, unspecified radius and ulna. A chronic bone infection affecting multiple areas of the forearm bones (radius and ulna) when the specific side (left or right) is not documented or specified. M86.339 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, M86.339 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, M86.339 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.
Use this code only when laterality cannot be determined from the medical record. Because M86.339 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 M86.339 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when laterality cannot be determined from the medical record
- •Query the provider if laterality is missing, as more specific codes are preferred
Clinical Significance
This diagnosis indicates chronic multifocal osteomyelitis affecting the radius and ulna when laterality is not specified, representing a significant infectious disease requiring long-term management. The condition poses risks for functional impairment and potential systemic complications if inadequately treated.
Documentation Requirements
- ✓Documentation of radius and ulna involvement (both bones)
- ✓Evidence of chronic infection (>6 weeks duration or recurrent)
- ✓Confirmation of multifocal pattern within affected bones
- ✓Radiological findings consistent with chronic osteomyelitis
- ✓Clinical symptoms (bone pain, swelling, decreased function)
- ✓Laboratory evidence (inflammatory markers, culture results when available)
- ✓Treatment documentation (antibiotic regimens, surgical history)
- ✓Absence of specific laterality documentation in the medical record