M00.09
BillableStaphylococcal polyarthritis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M00.09 an HCC code?
Yes. M00.09 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 M00.09
For M00.09to 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 M00.09 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M00.09 is the ICD-10-CM diagnosis code for staphylococcal polyarthritis. A bacterial joint infection caused by Staphylococcus bacteria affecting multiple joints throughout the body simultaneously. M00.09 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, M00.09 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, M00.09 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 when staphylococcal arthritis involves more than one joint site. Because M00.09 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 M00.09 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code when staphylococcal arthritis involves more than one joint site
- •Do not use additional M00.0x codes for individual joints when polyarthritis is documented; this code captures the multi-joint involvement
Clinical Significance
Staphylococcal polyarthritis represents a severe systemic bacterial infection involving multiple joints simultaneously, indicating hematogenous spread of Staphylococcus organisms. This condition carries significant morbidity with risk of joint destruction, sepsis, and permanent functional impairment requiring aggressive intravenous antibiotic therapy and often surgical drainage. The multi-joint involvement reflects high patient acuity and substantially elevated resource utilization for risk adjustment.
Documentation Requirements
- ✓Provider documentation identifying Staphylococcus as the causative organism (culture results, clinical diagnosis, or documented species)
- ✓Documentation of the affected joint with specific anatomical site
- ✓Clinical findings supporting joint infection (joint effusion, warmth, erythema, limited range of motion, fever)
- ✓Synovial fluid analysis results or culture and sensitivity reports when available
- ✓Treatment documentation (antibiotics, joint aspiration, surgical drainage/washout)
- ✓Assessment of whether the infection is acute or chronic, and whether it is a primary infection or secondary to another source
- ✓Documentation of all joints involved to support polyarthritis designation
Commonly Confused Codes
- •M00.0xx — Staphylococcal arthritis of individual joints; use individual joint codes only when a single joint is affected
- •M00.19 — Pneumococcal polyarthritis; differs by causative organism
- •M00.29 — Streptococcal polyarthritis; differs by causative organism
- •M00.89 — Polyarthritis due to other bacteria; use when organism is identified but is not Staphylococcus, Pneumococcus, or Streptococcus