Normally, the first thing that hits the ground (on your hands) is the palm/wrist area. Then you start your tumble, and whether you need knuckle protection depends on whether you plan to slap your knuckles on the asphalt. Simple truth is that you have no control, nor any idea, how your body is going to flail about. Whether you want gloves with this extra protection is up to you. Some people wear half boots and what amounts to golf gloves. Others suit up in armored jacket/pants and full-on race-style boots. It all depends on what level of security you desire.