Runner's Knee?

Perhaps I should be reading up on runner's knee. I ran for 50 min on the treadmill yesterday (about 7 km), varying the incline a bit to simulate hills. Today my left knee is kind of sore. Actually, my whole leg has a slightly numb feeling. It's not really painful and it isn't preventing me from walking or anything. It just feels...weird. No running for me today...going to play poker instead ;)