In what way can a feature of most backpacks cause a serious accident, (physical trauma) while being used normally?

When loading for groceries you can spill them all over the floor, if not loaded evenly.
Also I got my backpack caught on the railing going up the stairs. Good thing that I was aware and saved a trip to the ER.

@RedDeerGuy1 Ok, that’s one.

Once I was backpacking near a cliff. I slipped and the weight on my back caused me to lose my footing and fall over the side. Fortunately there was a big bush there that caught me so I just felt silly. My buddy helped me up and we went on our way.

One time I was skiing with a backpack on. As I started to scootch forward to get off a chair list, I realized my backpack was stuck in the slats in the backrest.

Fortunately I was able to pull it free at the last moment, otherwise I would have been hanging off a chairlift.

@All, Thanks so what feature of most backbacks?

The big and bulky feature, it seems.