I have been experiencing pain behind my knee (Left leg)... it is just above the knee and in the back ... I am active, but when I go for long walks, I can now only walk approximately 2 miles before the pain increases to a point where I have to stop, rest the leg. After about 10 minutes I am fine to walk again... but after another mile or so, I have to rest it again. It is not nerve pain, but always feels like I have extremely sore or stretched muscles or tendons. If I reach down and squeeze the affected area, the pain seems to lessen. Now, I am starting to feel some similar but minor pain behind the right knee. There is no swelling associated with this problem. Thank you