M65.859
BillableOther synovitis and tenosynovitis, unspecified thigh
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M65.859 an HCC code?
No. M65.859 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
M65.859 is the ICD-10-CM diagnosis code for other synovitis and tenosynovitis, unspecified thigh. Inflammation of the tissue lining the tendons or joint lining in the thigh when the specific side (left or right) is not documented. M65.859 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).
M65.859 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 laterality cannot be determined from documentation.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M65.859 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 laterality cannot be determined from documentation
- •Query provider if laterality is clinically relevant to treatment plan