Where to run without ruining your knees

Running is a great way to get and stay fit. It burns a ton of calories and challenges your whole body in a way that few other activities can. There's only one downside to running: it can ruin your knees if you're not careful.

But not surprisingly, where you run is of utmost importance to the health of your joints. Fitsugar has put together a list of the best and worst surfaces to run on, with 10 being the best for your knees and 1 being the worst:

• Grass: 9.5
• Wood chips: 9
• Dirt: 8
• Cinder track: 7.5
• Track: 7
• Treadmill: 6.5
• Asphalt: 6
• Sand: 4
• Snow: 2.5
• Concrete: 1

So running on the sidewalk isn't good -- stick to the treadmill, track or a grassy area instead. Where do you run?