Injury again

Since the last time I posted, I have been consistently running and have maintained the schedule that I described in a previous post. Last week (Saturday, February 16) trying to maintain the 6, 6, 8 mile schedule, I felt a pain in my left ankle. During the beginning of the run, it was a little sore but I ignored. nce I reached mile 5.5, it started to really hurt and I was trying to adjust my stride in order to alleviate the pain which resulted in pain in my right knee. Much to my dismay, I had to start walking. I completed 5.5 of the schedule 8 miles. I didn't twist my ankle or slip so I don't understand why it hurts.