Knee is basically one of the main joints that provides you the ability to walk. There are several ways to prevent or ease the knee pain (see Knee pain when descending a mountain), but I would like to dive deeper into one of the preventive measures, by using knee protectors.
I've noticed that there are different types of knee protectors out there: knee braces, knee sleeves, knee support, etc. Assuming that one does not have any knee problems, which of the knee protectors are best to prevent knee pain in a long distance hike with frequent ascent and descent trails?
Also, in order to maximize the effectiveness of knee protectors, should the user be wearing it in all situation while hiking (uphill, walking, descending, etc.)?