You are asking this question like its hipotetical, but it actualy happened in history many times.

It depends does knight have some kind of veapon or not. If not he is more hopless than antilope.

If it does than what kind of veapon? With spear he have a chance because people were surviving lion atacks with spear.

But know this lion is heavy animal that can run like a wind and jump like squirl. They are strong.

Man doesnt have much chance…