It is possible that you need to slow down. This is my experience: I tried C25K a couple of times and failed before I figured it out. I usually would fail around week 3 or 4. I think that I felt that I had been running a while, so I started to pick up the pace and an just would end up with sore knees that made me unable to continue. This last time around, when I wanted to speed up, I didn't. I kept at a pace that I considered uncomfortably slow, but it kept my knees from bothering me. I read somewhere on here or some other place on the internet, that different systems develop at different times and that often your cardiovascular system will be in better shape sooner than your musculoskeletal system. In my case, I felt like I could push it, but my musculoskeletal system wasn't ready yet. I also read that many times when a runner complains about knee pain, the pain is the result of muscle imbalance not the knee itself. I spent some time looking at knee diagrams and figured that this was likely the case with me. My quads weren't ready yet. I just kept it slow, I was to the point where if it didn't work this time I was going to give up trying and pick up a different sport. Going slow got me through the program and on to 10K training. I have also been able to increase my speed gradually without pain. Good luck figuring out the issue and being able to continue with your training.

You're a wise lady Snark

Building up the muscles around your knees is super important. That was the main thing I learned from going to physical therapy for my constant knee pain last year.