M00.821
BillableArthritis due to other bacteria, right elbow
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M00.821 an HCC code?
Yes. M00.821 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 M00.821
For M00.821to 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 M00.821 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M00.821 is the ICD-10-CM diagnosis code for arthritis due to other bacteria, right elbow. Infection and inflammation of the right elbow joint caused by bacteria other than the common ones typically associated with arthritis. M00.821 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, M00.821 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, M00.821 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.
Ensure documentation clearly identifies the right elbow as the affected site. Because M00.821 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 M00.821 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure documentation clearly identifies the right elbow as the affected site
- •Verify the bacterial organism is documented as 'other bacteria' rather than a specific pathogen like Staphylococcus or Streptococcus
Clinical Significance
Bacterial arthritis of the right elbow represents a serious infection of a weight-bearing joint that can lead to permanent disability if not treated aggressively. The elbow joint's complex anatomy makes this condition particularly challenging to treat and prone to complications.
Documentation Requirements
- ✓Confirmation of 'other bacteria' as causative organism (not typical pathogens)
- ✓Specific documentation of right elbow joint involvement
- ✓Laboratory evidence of bacterial infection (culture, gram stain, PCR)
- ✓Clinical signs of infectious arthritis (swelling, erythema, warmth)
- ✓Documentation of treatment with appropriate antibiotics
- ✓Range of motion limitations or functional impairment noted
- ✓Inflammatory markers elevation (ESR, CRP, WBC)
- ✓Exclusion of crystal arthropathy or autoimmune conditions
Commonly Confused Codes
- •M00021 — Streptococcal arthritis of right elbow (different bacterial type)
- •M00021 — Staphylococcal arthritis of right elbow (different organism)
- •M06.821 — Other specified rheumatoid arthritis of right elbow (autoimmune)
- •M19.021 — Primary osteoarthritis of right elbow (degenerative)
- •M24.821 — Other specific joint derangement of right elbow (mechanical)