I get some pain in my knees if I run on sidewalks slanted (for water drainage). How come knees are so sensitive to little changes?

Running. Some people's knees are very sensitive to running near the curb. Usually it is due to the excess stress caused by the angle. Some people will run 1/2 way and then turn around so that the knee is stressed on the opposite side. If this is a problem then you need to avoid these banked roads.