There are many reports about the snapping syndrome in the hip, shoulder, ankle, but the snapping knee has rarely been reported. In general, the symptom of this disease was relatively tolerable for that seldom requires operative treatment. We experienced one case of snapping knee, for which the pain, easy fatigability and feeling of instability on both knee joint were main complaints. During an exploratory operation, we confirmed the gracilis and semitendinosus tendon passing over the medial tibial condyle. The clinical, radiologic and operative findings were reviewed.