The barbell lunge is probably one of the most effective and yet most problematic barbell exercises. The benefits of doing exercises for your legs one leg at a time are numerous. You will develop better coordination, get rid of muscle imbalance between your limbs and last but not least become athletic in a very functional manner.
In fact after a good barbell lunge workout, done correctly, you will feel the exercise right in the areas sued for sprinting, jumping and climbing stairs.
The reason for the article however is that I see many people do barbell lunges with severe motion in the knee. This both hinders proper muscular balance of the complete leg musculature and places you at a greater risk of a knee injury.