Lowering the bar in a curved path around the knees (Figure 3), on the other hand, is inefficient, and as a result, it’s harder. Additionally, it causes you to set the bar down in front of the middle of your foot, which means you’ve got another variable to deal with before starting the next rep.
This problem arises when you try to keep a vertical torso when setting the bar down, which means you are primarily bending the knees to set it down, which in turn means that your knees become obstacles for the correct bar path.