I feel I am a seasoned runner, been doing long distance running since I was 14, currently 18 now. I was getting horrible shin splints, so I bought new high end running shoes and took a week off from running. Did 5 miles just fine, next day, after ~1mile, I couldn't walk from the pain in the lower part of my legs. In the past I would get knee pains from osgood slaughters disease, put I pretty much grew out of it. I do have flat feet, but I got orthotics, ones made for running and they are farely new and still fit me like a glove. Any ideas? Could it be the running on the pavement? Am I not giving myself enough time to rest (use to run 3.2 miles 4x a week in HS)? Is it I just started increasing my running to quickly from being stuck inside on a treadmill due to crappy weather?