M00.859
BillableArthritis due to other bacteria, unspecified hip
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M00.859 an HCC code?
Yes. M00.859 maps to Bone/Joint/Muscle/Severe Soft Tissue 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 M00.859
For M00.859to 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 M00.859 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M00.859 is the ICD-10-CM diagnosis code for arthritis due to other bacteria, unspecified hip. Bacterial infection causing inflammation and swelling in the hip joint when the specific side (left or right) is not specified or documented. M00.859 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, M00.859 maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.479. Under the older CMS-HCC V24 model, M00.859 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 39) with a community, non-dual, aged base RAF weight of 0.401. 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 laterality cannot be determined from the medical record. Because M00.859 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 M00.859 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Bacterial arthritis of unspecified hip is a medical emergency requiring immediate treatment to prevent joint destruction and systemic complications, though documentation lacks laterality specification. This condition demands urgent antibiotic therapy and often surgical intervention.
Documentation Requirements
- ✓Evidence of 'other bacteria' causing hip infection
- ✓Documentation of hip joint involvement without laterality
- ✓Bacterial culture or microbiological evidence
- ✓Clinical presentation of septic arthritis
- ✓Immediate antibiotic treatment documented
- ✓Assessment of mobility and weight-bearing capacity
- ✓Laboratory evidence of infection and inflammation
- ✓Attempt to specify laterality for complete documentation
Commonly Confused Codes
- •M00.851/M00.852 — Same condition with specific laterality
- •M00059 — Streptococcal arthritis of unspecified hip (different organism)
- •M00019 — Staphylococcal arthritis of unspecified hip (specific bacteria)
- •M06.859 — Other rheumatoid arthritis of unspecified hip (autoimmune)
- •M16.10 — Unilateral primary osteoarthritis of unspecified hip (degenerative)