Since advances in soluble biomarkers directly linked to synovitis pathology may well yield diagnostic tools for appropriate stratification in early phases of synovitis, IL-34 produced by knee OA FLS and released into the circulation and joint fluid of knee OA would be an additional inflammatory molecule involved in the development and progression of synovitis and cloud serve as a potential biomarker for knee OA synovitis. Here, IL34 is linked to synovitis.