When it comes to backpacks, physical therapist Karena Wu says people often put fashion in front of function.

"The fashion ones are cute because they have a design, but they are just one big sack and so your products inside can get bunched up on one side,” she says. “So you want to look for something where you have compartments so that you can distribute the load."

It is not just the inside of the backpack you have to consider.

"You also want a backpack that's got good, well-contoured straps,” Wu says. “A chest strap and a waist strap is also very helpful to help unload the spine, because as you're carrying the backpack on your shoulders, the transmission of forces is going down through the spine and it's tremendous."

A lot of kids carry overloaded backpacks and that can create problems.

"If you can leave some textbooks at home, that would be beneficial,” she says. “I know that sometimes they can't, so if you make sure the child is carrying the backpack closer to the trunk, that really helps with how heavy that backpack feels on their spine."

Looser straps on a heavy backpack can create big problems.

"A lot of forward head positioning, a lot of forward shouldering positioning, so they can have neck and shoulder pain,” Wu explains. “They can have mid-back all the way down to low-back pain."

And whether you have compartments or not, there is a better way to organize your backpack.

"Heavier items towards the trunk, so usually closer to the back of the backpack, and then the smaller items maybe around in the side pockets if possible,” Wu suggests. “You want, ideally, if you could find a backpack that's got some padding on the back that also protects the back from any sharp objects that might move around.”

She says backpacks should be proportional to the child - and she says she knows it is not popular, but students should use both straps. Your back will thank you years later.