The knees said I shouldn’t but I ran anyway. One lap went smoothly; then, halfway into the second lap, just as I turned the corner after the skateboard pits, a jabbing pain in my left knee. I stopped immediately. I’ve had too many injuries over the past year to want to push myself, to go beyond the point where all it takes is a day or two to be back in shape, ready for the next run. I took a left at the tennis courts and headed for home.