I spent an hour on Saturday and another hour today shoveling snow from my driveway, and my knee felt fine afterwards, although it is still sore when I first get up from sitting awhile.
Today was a very cold day due to a 20 mph or so wind. I made a mistake in not wearing gloves, and my fingers were very cold. I wore my heavy winter coat, and my body was warm. After I finished the driveway and sidewalk, I soaked my hands in cold water for a minute or so, and then I walked around my house while my fingers warmed up. The temperature was in the mid 20s (F), but the wind chill temperature was very cold. The snow was about 4-5 inches in depth, but it was very light and easy to shovel.