M86.8X3
BillableOther osteomyelitis, forearm
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.8X3 an HCC code?
Yes. M86.8X3 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 M86.8X3
For M86.8X3 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 M86.8X3 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.8X3 is the ICD-10-CM diagnosis code for other osteomyelitis, forearm. A bone infection (osteomyelitis) affecting the forearm (radius and/or ulna) that doesn't fit into other specific osteomyelitis categories. M86.8X3 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, M86.8X3 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, M86.8X3 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.
Document which bone(s) of the forearm are affected for clinical clarity, though the code encompasses both radius and ulna. Because M86.8X3 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 M86.8X3 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document which bone(s) of the forearm are affected for clinical clarity, though the code encompasses both radius and ulna
- •Ensure this is not acute or chronic osteomyelitis before assigning this 'other' category code
Clinical Significance
Other osteomyelitis of the forearm represents bone infection affecting the radius and/or ulna that doesn't conform to typical acute or chronic patterns. This condition can severely impact hand and wrist function due to the forearm's critical role in rotation and fine motor activities, requiring specialized treatment to preserve upper extremity function.
Documentation Requirements
- ✓Documentation of osteomyelitis affecting forearm bones
- ✓Clinical justification for 'other' classification
- ✓Specification of radius and/or ulna involvement
- ✓Supporting imaging demonstrating bone infection
- ✓Culture results or histopathological confirmation when available
- ✓Comprehensive treatment plan including antimicrobials
- ✓Assessment of forearm rotation and hand function
- ✓Documentation of atypical presentation features