i've started running alot of miles on the treadmill...mainly because of lack of time and the fact that i don't have that many trails around me....i'm just wondering is it harder on the knees than it would be if i was running on the roads....lately my knees have been bother me a lot...anyone else experiance knee problems while running on the tredmill...i'm also coming off of a semi long layoff...i'm running upwards of an 1:00 on the treadmill to...