This is where I've got to so far. Elbows were hard to have going the 'opposite' way, as arm joints rotate. So I've just gone for weird angles.
Joints go the way they do for a reason.
Knees were easier. Walking figures is going to be quite a challenge though! Probably base it on an ostrich walking. Doesn't matter if it looks odd - it's meant to be unnatural.(I swapped the legs & bodies, which is why there are gaps in the middle)