With the changes of the knee angles, the moving track of upper and lower edge point of the knee cap is similarly a parabola;

髌骨上、下缘点随膝角变化的运动轨迹类似于抛物线形状；

On another flight, the lady sat in front of me had her hand touching my knee cap .

另一次旅行，坐我前面的一位女士不停地摸我的膝盖。