Knee circles
Right back to high school gym class, huh? Stand with your knees slightly bent and roll them slowly in one direction as if you’re drawing a circle with them.
Repeat in the other direction. These are the best for keeping your knees loose and preventing injuries.
I do not stretch, ever (unless you count a quick bending at the waist and reaching to the sky, and bouncing on my tip-toes, which takes about 30 seconds). I once hurt myself stretching and couldn’t run for 2 weeks. I always do a warm up. I know there’s proper way to stretch and a wrong way, but I’d rather not risk it anymore.