这个膝盖问题怎么用英语向医生描述？（偶尔左膝会突然一软一麻，不能承重，但瞬间就恢复正常，不疼。）

偶尔左膝会突然一软一麻，不能承重，但瞬间就恢复正常，不疼. 有时运动前发生，有时运动后发生。

Occasionally my left knee got numb in a sudden and that knee cannot carry my body weight. I had to shift all my body weight to my right knee. 

But only after a few seconds, the left knee issue disappears. My left knee would work normally then. 

I do not feel pain in the whole process. Sometimes this happens before a workout, sometimes after a workout. 

Just these days this happend more often than before, which alerted me. 

谢谢！