How is the shoe on the knees? I will be using these almost everyday.

These don't have a lot of padding and can transfer a lot of shock up the legs. I believe that's the holy grail of mountain running footwear; finding the balance between transfering the feel of the ground so you can have accurate footwork, with soft cushion that helps protect your body. I believe these shoes are more of the cushionless high traction end of the spectrum. Very very grippy and super lightweight! Great for raceday, but I would want to train in something else until closer to race day.

It probably depends on the individual, but I start to get some swelling/discomfort in the patellar tendon (just below the knee) during lengthy, technical downhills on runs over 20-25 miles or so. Personally, I go with a slightly more protective shoe (like the FIreblade) for such efforts. Anything shorter and I'll be in my Crosslites -- I love em.