Walking lunges

When i do walking lunges or lunges in general I can't seem to get my back knee to touch the ground. I watch others around me and they can actually touch the back knee to the ground. What am i doing wrong and is there a way to improve my flexibility? Does the fact that I can't touch my knee make my lunges less effective? I stretch daily, have tried to widen my lunge so instead of lunging straight ahead I will lunge slightly out to the side and still I can't get my knee to touch the ground. What do you think?

Replies