Following 4 operations on my left knee after a serious injury playing football, it was found that my left leg was now shorter than my right leg. As a result, normal walking movement twisted my hips and resulted in constant lower back pain. I had to wear an insert in my left shoe with a 9mm platform to rectify the situation.
Within 6 months of taking up Iyengar Yoga my insert platform was reduced to 3mm. With a continual improvement, it is likely that at some point in the future I will not have to wear an insert at all.