M86.229
BillableSubacute osteomyelitis, unspecified humerus
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.229 an HCC code?
Yes. M86.229 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 M86.229
For M86.229 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 M86.229 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.229 is the ICD-10-CM diagnosis code for subacute osteomyelitis, unspecified humerus. A bone infection in the upper arm bone (humerus) of unspecified side that develops gradually over weeks to months, causing inflammation and potential bone damage. M86.229 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, M86.229 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, M86.229 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 only when the side of the humerus involvement cannot be determined from available documentation. Because M86.229 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 M86.229 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use only when the side of the humerus involvement cannot be determined from available documentation
- •Query the provider for laterality information to assign a more specific code if possible
Clinical Significance
Subacute osteomyelitis of unspecified humerus represents a bone infection with intermediate timeline affecting the upper arm bone without laterality specification. This diagnosis requires provider queries for laterality and monitoring to prevent chronic progression while preserving arm function.
Documentation Requirements
- ✓Documentation of humerus bone infection without laterality
- ✓Evidence of subacute infection timeline
- ✓Clinical presentation of humeral osteomyelitis
- ✓Imaging confirmation of humerus involvement
- ✓Laboratory support for ongoing infection
- ✓Provider query for laterality specification
- ✓Assessment of upper extremity function
- ✓Treatment plan for humeral bone infection
Commonly Confused Codes
- •M86129 — Other acute osteomyelitis of unspecified humerus
- •M86629 — Chronic osteomyelitis with draining sinus of unspecified humerus
- •M86329 — Chronic multifocal osteomyelitis of unspecified humerus
- •M86221/222 — Right/left specific codes when laterality available
- •M25519 — Pain in unspecified shoulder