M65.99
BillableUnspecified synovitis and tenosynovitis, multiple sites
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M65.99 an HCC code?
No. M65.99 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
M65.99 is the ICD-10-CM diagnosis code for unspecified synovitis and tenosynovitis, multiple sites. Inflammation of the tissue lining the tendons affecting multiple different areas of the body simultaneously. M65.99 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering disorders of synovium and tendon (m65-m67).
M65.99 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Use this code only when synovitis/tenosynovitis is documented in two or more distinct anatomical sites.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M65.99 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when synovitis/tenosynovitis is documented in two or more distinct anatomical sites
- •Document all affected sites clearly in the medical record to justify the use of this multiple sites code