This disease is also called Osgood-Schlatter disease.It often occurs in young people at the age of 10 - 15,mostly in boys, especially in those boys who often take part in strenuous exercises. A youngster is not rich in kidney qi and not firm in tendon and bone, and his epiphysis of tibial tuberosity is not fused. So, when he practices a violent jump, running and ball games, his quadriceps muscle of thigh will contract strongly, pulling the epiphysis of tibial tuberosity through patellar ligaments, leading to chronic injury, local stagnation of qi and blood and disturbance of blood circulation. As a result, the epiphysis of tibial tuberosity loses its nourishment of qi and blood,hence, there occurs ischemic necrosis.