M45.A7
BillableNon-radiographic axial spondyloarthritis of lumbosacral region
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M45.A7 an HCC code?
Yes. M45.A7 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease under the CMS-HCC V28 risk adjustment model (and Rheumatoid Arthritis and Inflammatory Connective Tissue Disease 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 M45.A7
For M45.A7to 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 M45.A7 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M45.A7 is the ICD-10-CM diagnosis code for non-radiographic axial spondyloarthritis of lumbosacral region. Inflammation of the spine joints where the lower back meets the sacrum that doesn't show typical changes on standard X-rays. M45.A7 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering spondylopathies (m45-m49).
Under the CMS-HCC V28 risk adjustment model, M45.A7 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease (HCC 93) with a community, non-dual, aged base RAF weight of 0.175. Under the older V24 model, M45.A7 mapped to the same category but with a base RAF weight of 0.307 — 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.
Document the specific involvement of the lumbosacral junction to differentiate from isolated lumbar or sacral involvement. Because M45.A7 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 M45.A7 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document the specific involvement of the lumbosacral junction to differentiate from isolated lumbar or sacral involvement
- •This region is frequently affected in spondyloarthritis; ensure proper anatomical specificity
Clinical Significance
Non-radiographic axial spondyloarthritis of the lumbosacral region encompasses both lumbar spine and sacroiliac joint inflammation detectable by MRI before X-ray changes occur. This represents classic early axial spondyloarthritis requiring prompt biologic therapy to prevent progression.
Documentation Requirements
- ✓MRI evidence of both lumbar spine and sacroiliac inflammation
- ✓Normal or grade 1 sacroiliitis on conventional radiographs
- ✓Clinical symptoms of inflammatory back pain
- ✓Documentation of morning stiffness duration and characteristics
- ✓Assessment of spinal mobility and sacroiliac joint stress tests
- ✓Response to anti-TNF or IL-17 inhibitor therapy
- ✓ASAS criteria fulfillment documented
- ✓Disease activity measures using validated instruments
Commonly Confused Codes
- •M45.7 — Radiographic ankylosing spondylitis when structural changes visible
- •M45.A6 — Lumbar region when sacroiliac involvement is not present
- •M45.A8 — Sacral region when lumbar spine is not involved
- •M46.1 — Sacroiliitis without lumbar spine involvement
- •M54.5 — Mechanical low back pain without inflammatory features