Never had any knee pain before. After about 5 mile walk, August 5, 2008, the next morning both knees were hurting. The right cleared up in a week. But the left has been stiff and painful ever since, also calf muscle and heel gets tight as drum too. I had been at resort at the time and in the common hot tub prior to onset. Knee specialist ordered MRI, and saw knee specialist. He advised no damage, everything looked pretty good, the radiologist's report noted some inflamation, which (rightly or wrongly?) he attributed to arthritis. I am not comfortable with that diagnosis. As this was not a gradual thing...but overnight onset. Anyone have any other suggestions. On walks, the longer I walk the better it gets, until no discomfort at all. If I sit, both knees now get stiff, and have to take stutter steps to get going.