All was going well until I did week 3, run 2 and I felt a slight twing in my right knee, then after a days rest, I completed week 3, run 3. But after that run, my left knee was aching and I was in a lot of discomfort. During the night the ache in my left knee was unbearable. The only things that changed between run 2 and run 3 was that I was running with a friend who recommended that I do some stretches before the app starts with the warm-up walk (with Laura). I have never done stretches before I set off, I just follow Laura's instructions and warm up using the brisk walk. I always stretch when I get back after the run though. And the second thing is that I brought some new trainers which were fitted out in a sports shop (no measurements were taken, the guy fitted me just using how I was standing with knees slightly bent). In the town where the shop is, this guy is very well liked and trusted on all things sports related. I brought ON trainers and paid three figures for them. After week 3, run 3, my left knee is feeling sore and aching. This morning I completed week 4, run 1 and I managed it fine. But I'm now limping on my left knee. It is aching and feels painful, though the pain is not constant. The pain and ache is around the front of my kneecap and it goes down a bit on the front of my leg and just on the inside side of my kneecap. Is this normal aches and pains or have I done something? I am gutted.