M01.X12
BillableDirect infection of left shoulder 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.X12 an HCC code?
Yes. M01.X12 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.X12
For M01.X12to 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.X12 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M01.X12 is the ICD-10-CM diagnosis code for direct infection of left shoulder in infectious and parasitic diseases classified elsewhere. Direct infection of the left shoulder joint resulting from an infectious or parasitic disease classified elsewhere. M01.X12 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.X12 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.X12 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.
Requires a primary diagnosis code for the underlying infectious or parasitic disease. Because M01.X12 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.X12 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Requires a primary diagnosis code for the underlying infectious or parasitic disease
- •Laterality is specified; ensure documentation clearly indicates left shoulder involvement
Clinical Significance
This code represents a direct joint infection in the left shoulder secondary to an infectious or parasitic disease classified elsewhere, requiring dual coding. It indicates a serious complication that significantly impacts patient mobility and quality of life, requiring aggressive antimicrobial therapy and potential surgical intervention.
Documentation Requirements
- ✓Documentation of direct infection involving left shoulder joint
- ✓Evidence of underlying infectious or parasitic disease with appropriate code from A00-B99
- ✓Confirmation that joint infection is directly caused by the underlying disease, not a secondary bacterial infection
- ✓Clinical signs of joint inflammation (pain, swelling, reduced range of motion)
- ✓Laboratory evidence supporting infection (elevated WBC, ESR, CRP)
- ✓Imaging studies showing joint involvement (X-ray, MRI, or CT)
- ✓Microbiological studies if available (joint fluid culture, tissue biopsy)
- ✓Treatment plan addressing both underlying disease and joint infection
Commonly Confused Codes
- •M00.912 — Pyogenic arthritis, left shoulder (bacterial joint infection not related to underlying classified disease)
- •M25.512 — Pain in left shoulder (joint pain without confirmed infection)
- •A18.02 — Tuberculous arthritis of other joints (specific tuberculous joint infection)
- •B69.89 — Other cysticercosis (specific parasitic infection that could cause joint involvement)