If you play contact sports, such Arctic Blast Review as football, a well designed knee brace can really help protect you from being hit from the side, forcing your knee into an unnatural position. When you get hit from the inside, or outside of your knee, you can suffer an ACL tear, MCL tear, or meniscus tear (if not all of the above). This can end your season very quickly.
One interesting point is that some football players refer to their legs as their money makers, and if your knee is hurt, then you may just be bankrupt! If you suffer an injury because of an excessive forward to backward movement, then knee supports can help protect you as well. If the knee brace has a hinge, many times this hinge can help eliminate excessive forward to backward movements.
For other sports such as running, basketball, soccer, or skiing for example, you have some different challenges, especially because these are non contact sports. One thing remains the same though - If you need to help protect your knees because you will be doing some quick stopping, starting, jumping or landing then a knee brace may become your new best friend. We all like to think that we will be able to control ourselves and resist an injury of some kind, but the high speed at which you play these sports may jeopardize your knee very quickly.