Peregrinus
Active Hunter
The cupped side goes up to cover the knee in case the knee impacts anything.
These do that regardless of orientation, strapped around the top of the calf with the round part projecting up, or strapped around the bottom of your thigh with the round part projecting down. Main differences are comfort and the fact that worn "upside-down" like this, one can kneel. Worn "correctly", the knees tend to get in the way of that.
--Jonah