M01.X42
BillableDirect infection of left hand in infectious and parasitic diseases classified elsewhere
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M01.X42 an HCC code?
Yes. M01.X42 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 M01.X42
For M01.X42to 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 M01.X42 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M01.X42 is the ICD-10-CM diagnosis code for direct infection of left hand in infectious and parasitic diseases classified elsewhere. An infection in the left hand joint caused by a disease classified elsewhere, such as tuberculosis or a parasitic infection. M01.X42 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering infectious arthropathies (m00-m02).
Under the CMS-HCC V28 risk adjustment model, M01.X42 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, M01.X42 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 the specific underlying infectious disease to assign the appropriate secondary code. Because M01.X42 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 M01.X42 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document the specific underlying infectious disease to assign the appropriate secondary code
- •This represents a secondary joint infection manifestation of another primary infectious condition
Clinical Significance
Direct infection of the left hand joints resulting from infectious or parasitic diseases classified elsewhere represents a serious condition with significant functional implications. The hand's complex anatomy and critical role in daily activities make this diagnosis particularly important for maintaining quality of life and independence.
Documentation Requirements
- ✓Specific documentation of left hand joint infection
- ✓Primary diagnosis of underlying infectious or parasitic disease (A00-B99)
- ✓Clear evidence that hand infection is direct result of classified disease
- ✓Clinical assessment documenting hand joint inflammation and functional limitation
- ✓Laboratory evidence supporting infectious process and systemic inflammation
- ✓Radiographic studies confirming hand joint involvement
- ✓Joint aspiration results including culture and sensitivity when performed
- ✓Comprehensive treatment plan for both systemic and local hand infection
Commonly Confused Codes
- •M00.942 — Pyogenic arthritis, left hand (routine bacterial joint infection)
- •M25.542 — Pain in left hand (joint symptoms without infectious cause)
- •M01.X41 — Direct infection of right hand in infectious diseases classified elsewhere
- •M02.142 — Postdysenteric arthropathy, left hand (reactive arthropathy following dysentery)