M01.X39
BillableDirect infection of unspecified wrist 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.X39 an HCC code?
Yes. M01.X39 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.X39
For M01.X39to 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.X39 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M01.X39 is the ICD-10-CM diagnosis code for direct infection of unspecified wrist in infectious and parasitic diseases classified elsewhere. An infection in the wrist joint (side not specified) caused by a disease classified elsewhere, such as tuberculosis or a parasitic infection. M01.X39 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.X39 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.X39 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.
Use this code only when the specific side (left or right) of the wrist is not documented or is bilateral. Because M01.X39 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.X39 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when the specific side (left or right) of the wrist is not documented or is bilateral
- •Always pair with a secondary code identifying the underlying infectious or parasitic disease
Clinical Significance
This code captures direct wrist joint infection secondary to classified infectious or parasitic diseases when laterality is not documented, indicating incomplete clinical documentation. The condition represents significant risk for functional impairment of the hand and wrist complex requiring intensive treatment.
Documentation Requirements
- ✓Documentation of wrist joint infection without laterality specification
- ✓Required underlying infectious or parasitic disease code as primary diagnosis
- ✓Evidence that joint infection is direct result of classified disease
- ✓Clinical examination findings consistent with infectious wrist arthropathy
- ✓Laboratory markers supporting infectious and inflammatory processes
- ✓Imaging studies demonstrating wrist joint involvement
- ✓Microbiological studies from joint aspiration if performed
- ✓Treatment plan addressing both systemic infection and joint manifestations
Commonly Confused Codes
- •M00.939 — Pyogenic arthritis, unspecified wrist (bacterial infection not from classified disease)
- •M25.539 — Pain in unspecified wrist (joint symptoms without infectious cause)
- •M01.X31 — Direct infection of right wrist (when laterality is actually documented)
- •M01.X32 — Direct infection of left wrist (when laterality is actually documented)