ABSTRACT Objective To access the relevance with medial meniscal extrusion and knee osteoarthritis by high frequency ultrasound . Methods Sixty-six patients with symptoms of knee joint, 41 cases of them with osteoarthritis, 25 cases of them without osteoarthritis .And fifteen cases of healthy subjects as controls were enrolled. Compared the medial meniscus extrusion among three groups .Selected the more severe knee to have a check in the abnormal group , randomly selected one knee for check in the control group .Results 41 knees with osteoarthritis , 25 knees with Symptoms of knee joint but without osteoarthritis,15 knees were controls. The medial meniscus extrusion values were 5.13±1.30mm、2.82±0.82mm、1.42±0.55mm.Medial meniscus extrusion differences between groups was statistically significant (P < 0.05).Conclusions There were close correlation between knee osteoarthritis and meniscal extrusion. They may be a complementary role .It would be great significant in prevention, early diagnosis , selection of treatment and monitoring of treatment effect with knee osteoarthritis using musculoskeletal ultrasound to evaluate meniscus extrusion degree with knee osteoarthritis in the future.