M86.042
BillableAcute hematogenous osteomyelitis, left hand
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.042 an HCC code?
Yes. M86.042 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 M86.042
For M86.042 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 M86.042 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.042 is the ICD-10-CM diagnosis code for acute hematogenous osteomyelitis, left hand. A bone infection in the left hand caused by bacteria spreading through the bloodstream, typically affecting the small bones of the hand. M86.042 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, M86.042 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, M86.042 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.
Confirm documentation clearly indicates 'left' hand to differentiate from M86.041. Because M86.042 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 M86.042 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm documentation clearly indicates 'left' hand to differentiate from M86.041
- •Document which specific hand bones are affected if possible for clinical clarity
Clinical Significance
Acute hematogenous osteomyelitis of the left hand represents serious bloodstream-spread infection to the complex small bones of the left hand, requiring immediate aggressive treatment to preserve function. This diagnosis indicates high risk for compartment syndrome, joint destruction, and permanent loss of hand function with significant impact on activities of daily living.
Documentation Requirements
- ✓Documentation of acute osteomyelitis specifically in left hand bones
- ✓Clear evidence of hematogenous spread of infection
- ✓Clinical examination findings of left hand involvement
- ✓Imaging studies demonstrating left hand bone infection
- ✓Microbiological studies including blood and tissue cultures
- ✓Intensive treatment with IV antibiotics and surgical intervention
- ✓Assessment for compartment syndrome and neurovascular compromise