I know my dad used to play a similar game when he was in the Scouts - they called it "splits".
You stood with your legs together, facing your opponent. Then you'd throw the knife, and wherever it landed, they had to move the closest leg to that position. Eventually, you'd both be doing the splits rather uncomfortably. The first one to fall over lost. Alternatively, if the knife fell between the opponents legs, they could stand feet together again.
As a slight variation on this theme, being that they were playing it during Scout camps, they used hand-axes instead....