I purchased these for skiing and the occasional biking. I have had some problems with my knees in the past and thought these might help. I was pretty skeptical but i figured what the heck if they didnt work i could return them. They fit just like compression pants and after two days of skiing on them i had no knee pain, which is when i would normally start to feel it. On the fourth day when i normally would take a day off i was still going strong. That little added support really helped me and i would reccommend these to anyone with joint problems in their legs (if they dont help then backcountry will take them right back).
NOTE: Im 5'11" 170lbs athletic build and i went with the MEDIUM which fits great.