Your hips will become open and upper body twisted.
If your hips open up your back foot will easily slide off line both when pulling it forward after the step and also if and when returning to a kamae position.
Push from your back leg and concentrate on your inside hip to maintain a straight centerline when making big forward movements.
The knot on your belt should always be facing straight forward.
By pushing your body forward from your back leg, your inside hip will be locked forward keeping your back foot moving in a straight line.
Note: when returning or moving backwards it is the same - Don't think of stepping back with your rear leg. Using your knee push your body back with your front leg.
Think of zenshin dosa (forward movements) like a rear-wheel drive performance car - the power comes from the back leg, not a front-wheel drive K-car.
Push with the back leg, then quickly pull your back foot up using your front knee.The timing of the bending of the knee and pulling of the back foot must be smooth and simultaneous.