M86.242
BillableSubacute osteomyelitis, left hand
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.242 an HCC code?
Yes. M86.242 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 M86.242
For M86.242 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 M86.242 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.242 is the ICD-10-CM diagnosis code for subacute osteomyelitis, left hand. A bone infection in the left hand that develops over weeks to months, causing inflammation and potential bone damage. M86.242 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, M86.242 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, M86.242 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.
Verify laterality is documented as 'left hand' in the clinical record before assigning this code. Because M86.242 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 M86.242 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify laterality is documented as 'left hand' in the clinical record before assigning this code
- •Confirm the infection is subacute (not acute or chronic) and document the specific bone affected when possible
Clinical Significance
Subacute osteomyelitis of the left hand represents a bone infection with gradual onset affecting the complex hand anatomy over weeks to months. This condition threatens fine motor function and grip strength, requiring careful treatment to preserve hand dexterity and prevent chronic disability.
Documentation Requirements
- ✓Specific identification of left hand bone involvement
- ✓Documentation of subacute infection timeline
- ✓Clinical evidence of hand bone infection
- ✓Imaging confirmation of osteomyelitis in hand bones
- ✓Laboratory evidence of ongoing infection
- ✓Assessment of hand function and grip strength
- ✓Documentation of fine motor impact
- ✓Treatment plan preserving hand mobility