I have recently developed a muscle pain behind my right knee area. It feels like a muscle that has been pulled or over strained - In my estimation it is not a knee issue, but most likely a muscle in the very upper lower leg thru calf area. I use clipless pedals and it only is apparent on the upstroke. I also can notice it walking up stairs, the lifting motion of the leg to the next step.
Background: I have ridden 900mi in the past 3mo - 9mi twice a workday with never a muscle problem. I ride at 110rmp cadence. The pain came suddenly on 7/19. That was my last day riding for 10days as I had to travel - I thought this was good as it would give it a rest. I did ride on a trainer one day at the hotel with no clips and there was no pain (no upstroke) The whole 10days I felt no pain. Then yesterday 7/26 the pain was still there after the first 9mi ride. I generally try to keep an even smooth cadence (no pushing or pulling) However if I focus on just pushing down on pedal I can avoid the upstroke pain.
Any thoughts/advice on treating it? Do I need to take time off? Could switching to platform pedals give the rest needed?