The position of the legs is set wrong. Your position is probably in the knee, or somewhere high. I'd suggest you set the position to the location of hip and hope for the best. I've never created a mech myself.
EDIT: Yes, now I checked the linked screenshots. Your leg position is at 0,0,0 which makes them move around that position. The yellow ball, that indicates the position, should be located at the point where you want to make the leg move. For example, to make that correct, the yellow ball should be located at the top of the leg.
Am I here, or am I not, are you sure, or are you not. - Funnis