How to Lunge - Variations, Modifications and Mistakes

Another mistake that could cause knee problems involves your stance. Each person will have a different stance based on his height, leg length and what feels comfortable. However, keeping the feet too close together puts much of the force on the knees rather than on the glutes, hamstrings and quads, which is where it should be. Taking the feet too far apart may compromise flexibility in the back leg and add to an already unstable position.

You can avoid this by watching your form in a mirror or, if you don't have one available, check your stance by getting into a lunge position. Lower all the way down, resting the back knee on the floor (make sure you're on a mat or other padded surface). Doing this allows you to check and see if you have a 90-degree angle in both knees. If you don't, you can adjust your stance.