Objective: the aim was to determin the synovitis imaging in knee Osteoarthritis (OA) on Ultrasound (US), and relationship between synovitis with knee pain, joint effusion, Vss, stage OA on X-ray. Subjects and Methods: Cross-sectional study. 60 patients with 109 knee OA which were dianosigsed by the ACR-1991 criteria. Results: On ultrasound (US) showed 71/109 (65,1 percent) synovitis in knee OA, ultrasonographic synovitis was defined as synovial thickness 4mm, diffuse appearance, increased vascularity in synovial (power or colour Doppler signal). Synovitis in 75.5 percent severe painful knee OA. 100 percent Vss increasing and 72.6 percent knee efusion has synovitis. Especially, on ultrasound assessment synovitis equal with MRI. Conclusion: US is becoming an essential tool the synovitis on knee OA. Results of this stydy suggest that ultrasonographic synovitis correlated statistically (p 0.05) with knee pain, joint effusion, Vss increasing and stage on X-ray (Kellgren - Lawrence).