Jus to back up what the guys have already said, itlooks like your rig was setup at the knees, with a straight leg. You will need to create a bend, detach the skin from the model and then go in and move the joints to this kinda position. Use the move tool and press inset to move the joints about, then inesrt again, do this with each one to reposition it. Also check the local rotation access as well.