M01.X0
BillableDirect infection of unspecified joint 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.X0 an HCC code?
Yes. M01.X0 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.X0
For M01.X0to 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.X0 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M01.X0 is the ICD-10-CM diagnosis code for direct infection of unspecified joint in infectious and parasitic diseases classified elsewhere. Direct joint infection from an infectious or parasitic disease that is classified elsewhere in the ICD-10 system, affecting an unspecified joint. M01.X0 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.X0 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.X0 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.
This is a manifestation code; always code the underlying infectious/parasitic disease first. Because M01.X0 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.X0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a manifestation code; always code the underlying infectious/parasitic disease first
- •Use when the primary condition is documented but the specific joint is not identified
Clinical Significance
Direct joint infection in infectious diseases classified elsewhere indicates that a systemic infection has directly invaded an unspecified joint, requiring treatment of both the underlying disease and the joint infection. This represents a serious complication of the primary infectious condition.
Documentation Requirements
- ✓Documentation of underlying infectious or parasitic disease
- ✓Evidence of direct joint involvement from the primary infection
- ✓Joint location specified as unspecified
- ✓Treatment of both primary disease and joint infection
- ✓Code first the underlying infectious disease
- ✓Clinical signs of joint infection secondary to primary disease
- ✓Laboratory evidence supporting direct joint involvement
- ✓Exclusion of reactive arthritis versus direct infection
Commonly Confused Codes
- •M01.X1-M01.X9 — Same condition with specific joint involvement
- •M02.30 — Reiter's disease, unspecified site (reactive, not direct)
- •M03.6 — Reactive arthropathy in other diseases (immune-mediated)
- •M00.9 — Pyogenic arthritis, unspecified (bacterial, not secondary)
- •M36.0 — Dermato(poly)myositis in neoplastic disease (autoimmune)