My son is a runner and has participated in several marathons. While I think running is good for you, I think it has also taken a toll on his body as his feet pound the pavement every day.
He has also had his share of injuries and this includes some leg and knee pain that is a result of injuring his iliotibial tract.
Because of this, he has to do iliotibial band exercises on a regular basis to prevent further injury and allow him to run on a regular basis.
I keep hoping he will find a way to exercise that is not so hard on his body, but he seems to still be pretty addicted to running at this point.