As a personal trainer in Austin, I've worked with many of our clients to develop a better way to lunge without knee pain. Most people, our clients included, like to step forward to lunge. The problem with the step forward lunge is that most of your weight ends up out in front of your toes - that puts an incredible amount of pressure on your knees and can lead to pain.
Instead, we like to have our clients shoot for a more solid and safer position for the knee: either right above or slightly behind your toes. So, instead of having you step forward into a lunge, we prefer to have you step backwards, find your balance and slowly bend your back knee towards the floor. By doing a lunge this way, it helps us with two things: First, you instantly keep more of an upright posture. Second, you can now see the position of your knee and make sure that it's not coming out over your toes. Now you should be able to safely and painlessly lunge.
If you have any questions or comments, please do not hesitate to contact Pat Mercer at Human Machine Athletic Club.