By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) - If you are still shopping for the kids, and I know many of you are, you might be getting ready to purchase a backpack. There are many styles to choose from but my biggest concern is that you should get one that distributes the weight across the back equally. These backpacks have two straps and usually there is padding in the straps.

Unfortunately many kids just sling the back pack over one shoulder and don’t distribute the weight. Another issue is that many students don’t know that they have to lift at the knees. You want to keep your back straight and not bend over and lift.