A69.23
BillableArthritis due to Lyme disease
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is A69.23 an HCC code?
Yes. A69.23 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 A69.23
For A69.23 to 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 A69.23 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
A69.23 is the ICD-10-CM diagnosis code for arthritis due to lyme disease. This is joint inflammation and pain caused by Lyme disease, a tick-borne infection transmitted by infected deer ticks. The infection spreads to the joints and causes arthritis symptoms like swelling, stiffness, and discomfort. A69.23 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other spirochetal diseases (a65-a69).
Under the CMS-HCC V28 risk adjustment model, A69.23 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, A69.23 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.
Always verify that Lyme disease has been confirmed with appropriate testing (serology or Western blot) before coding this condition, as it requires documented evidence of the infection. Because A69.23 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 A69.23 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Always verify that Lyme disease has been confirmed with appropriate testing (serology or Western blot) before coding this condition, as it requires documented evidence of the infection
- •This code should only be used when arthritis is a direct manifestation of Lyme disease; if arthritis exists independently, use the appropriate arthritis code instead
Clinical Significance
Lyme arthritis is the most common late manifestation of Lyme disease, occurring weeks to months after the initial tick bite. It represents a significant chronic infectious disease burden, typically affecting large joints (especially the knee), and requires specific antibiotic therapy distinct from typical inflammatory arthritis management.
Documentation Requirements
- ✓Positive Lyme serology (two-tier testing: ELISA followed by Western blot confirmation)
- ✓Specific joint(s) involved with laterality (knee is most common)
- ✓Clinical presentation: episodic or persistent joint swelling, effusion, pain
- ✓Timeline of Lyme disease progression (early localized, early disseminated, late disseminated)
- ✓Prior treatment history and response to antibiotics
Commonly Confused Codes
- •M13.80 (Other specified arthritis, unspecified site) — Nonspecific arthritis code; use A69.23 when Lyme etiology is confirmed
- •M12.50 (Traumatic arthropathy, unspecified site) — Mechanical joint derangement, not infection-related
- •A69.20 (Lyme disease, unspecified) — General Lyme disease code without specifying arthritis manifestation; use A69.23 when arthritis is the documented manifestation
- •M02.30 (Reiter disease, unspecified site) — Reactive arthritis; Lyme arthritis is a direct infection, not a reactive process