I have been riding for over a year, and have been riding my road bike since July. All of a sudden I am getting pain in my left knee when I am about 20 miles into the ride. I have not ridden as much during the winter as I did during the fall - could it be a simple lack of 'knee endurance'? The pain is only in my left knee - on the outside. Nothing has changed, which is very annoying.

I do not ride with clipless pedals, but I do have some and will try that to see if it changes anything. I will also try riding more often for less distance.

Does anyone have any advice or thoughts about this? Thanks in advance!