I think meditative positions can depend on the type of mediation or the goal of the meditation, but there are no rules. This is certainly the case in my experience.

If I am intending to ground/earth myself I find that standing is the most effective position for me - as my feet are connected to the floor ('earth') and my body is straight and uncrossed. During this type of meditation I use any discomfort in my feet for example, as feedback that I am feeling a connection to the earth - so it can work for you. It depends how long you're standing for really. And the deeper you go into the meditation/trance you feel less discomfort.
For centering meditations I like to sit cross legged as I find this most effective, whereas in most cases when I meditate I find it easiest just to lie straight down on the floor.