Went to my ortho doc yesterday. Brought info on Asterisk and CITI2 knee braces for his review. He was a pretty with it / cool guy and here is what he had to say. "No brace has been clinically proven to prevent ACL/MCL, etc. type injuries and that he was unaware of any studies done on dirt bikers or mountain bikers relative to how knee injuries occurred. He said the main thing they help with is the gray matter between the sides of your helmet." He did say they will remind you to take care of your knees while wearing them and that they will offer abrasion protection in the event of a fall. He also said that building up the muscle in and around the knee was most important. He showed me some exercises to build up muscle around the knees. My knees are fine but I think I will still be getting a pair of Asterisks if for no other reasons than the abrasion protection and the gray matter factor! I would be interested in hearing opinions of others without prior knee injuries - I'm relatively sure of the position those with prior injuries will take.