About six years ago, on the 4th of July, I tore a ligament in my right knee trying to do a spin, while swing dancing on concrete, wearing tennis shoes. Not smart.
I had to use a cane for about six months and had no problems while flying.
It is pretty much healed now, but it still can give me grief on a bad day. Now I am having problems with my right knee. I can still do lunges and squats but sometimes have trouble with stairs. Go figure.