In order to avoid the knees jutting forward and the lumbar spine flexing (and those joints being driven out of optimal alignment and receiving excessive stress) you need to emphasize loading the hips. When deadlifting, keep the shins vertical, like you are standing in cement up to the top of your shin, and push the hips back . The shoulders should come forward, in front of the toes, so you can maintain balance (see first picture).
Once the bar reaches the bottom of the knees (you need a minimum amount of flexibility in the hips to get this far and not round your back), you need to keep the chest up, shoulder blades back, back flat, and sit back to keep the tension in the hips. Keep the shins vertical as you descend further (see the second picture). This is the hardest part of the deadlift. Frequently, the knees will jut forward and the lumbar spine will round, therefore unloading the hips.
From the side, your deadlift should look like the number "4" at the bottom (if you had bumper plates, this is where they would touch the ground). This is the proper, safe, and effective technique that I teach my clients.
- The bar is close to the shins and the shins are vertical.
- The shoulders are directly over the bar.
- The head is up, the shoulder blades are back and down, and the back is flat (the angle of the back is the same in both pictures).
- The tight angle of the hips, indicates proper loading.