Objective To explore the association of ultrasound score in the severity of knee osteoarthritis. Methods 120 patients with osteoarthritis of the knee were collected and 50 healthy adults were collected at the same time. The correlation between the ultrasonic score and the severity of the patients with osteoarthritis of the knee were analyzed. Results The score of ultrasound in patients with knee osteoarthritis was significantly higher than that in healthy adults (6.93±1.76 vs. 1.73±0.56,P=0.000). The patients with knee osteoarthritis were significantly correlated with the fluid depth of the patellar capsule, the depth of the fluid of the patellar capsule, the depth of the articular cavity and the thickness of the synovial membrane (r=0.265, 0.216, 0.310 and 0.255, P=0.004, 0.035, 0.000 and 0.012), and had a significant negative correlation with Lyshsolm (r=-0.381, P=0.000). When compared with patients with negative blood vessels in proliferative synovium, ultrasound scores in patients with positive synovial vessels were significantly increased (7.43±1.61 vs. 5.58±1.42, P=0.000). Conclusion The ultrasound score is correlated with the severity of knee osteoarthritis.