Spears were the predominant weapon for most of history for a very good reason: your enemy can't stab you if they can't get to you. A wise man once said, "You got reach and you got sharp. What else do you need?"
The problem is that once an enemy DOES get past the sharp end of the stick, you have a problem. As this Demacian knight is learning, the pole of the spear is pretty easy to just grab and disable. The good news for him, I suppose, is that Katarina has no interest in killing him just yet. The bad news is that he may rather he had just died...