Chicken or Egg?

Which came first, the Chicken or the Egg?

I ran today. My knee started hurting on step #3. It went like this... power up the machine, push a button, step onto the moving track. Step, step, ache, step, ache, step, pain, step, Pain, step, PAIN... until the 10 minutes & slightly over 1 mile was complete and I hopped down the stairs without bending the knee, and didn't step fully on it for a solid ten minutes. After the ten minutes I had some aches all day, but nothing serious, and I was able to get up and down the stairs.

I can't figure out though, if it was real pain or "head" pain. I spent the entire run wondering when my knee was going to stop supporting my weight and I was going to crash into T's floor when that happened. "Now? Is it going to happen.... NOW?.... Now?...." Is the wondering what lead to the pain? Or is the pain what lead to the wondering?

I need to run with someone who can talk for 10 minutes straight. That's really what I need. Someone who can talk to me about something NOT running. Tomorrow I am going to drop the girls at school and drive to Glen Allen to run with T. It has to work. Has To. No pressure T.