Not sure about ones to fix a knee problem, but when I got them for my foot problems they were like heaven.  Sooooo comfortable they felt like walking on clouds.  Hope that is true for your new ones. 

They're great!  But they take a little adjusting to.  It'll feel weird at first.  My doctor told me to start out only wearing them a couple hours a day and build them up. 

Body adjustment has a lot to do with the correction issue and the design of the orthotic.  Like karozel, I'm not familiar with what's involved with correcting a knee issue.  Did your doctor / podiatrist give you any information when they were ordered?

I had to get mine for plantar fasciitis (strong arch support) and pronation.  Because it was designed to also change the way I step and reduce the give in arch, it had a profound effect on my lower back for a while (was very sore), but my feet saw immediate relief.  The back soreness went away after about 6 weeks, and yoga combined with ibuprofen helped with pain in the meantime.

my 11 year-old daughter got orthotics a month ago for the very same as santonacci. she hardly notices them in her shoes and has had substantial relief, even though it is summer and doesn't wear them as much as she will in the colder months. her only complaint is that they make her feet hot.

Original Post by deleseo:

...even though it is summer and doesn't wear them as much as she will in the colder months. her only complaint is that they make her feet hot.

 There are sandals out there that accomodate orthotics.  I got some Bite sandals, and I love them - the footbed is removable so that you can put an orthotic in to the inset sole (look for the Orthosport removable footbed logo).

thanks for the tip i'll see if i can find some of those sandals for her

the first two weeks was weird for me. but now, after almost 8 years of wearing them, i cant live without them.  they didn't relieve all the pain but it sure helped. of course i need new ones. i got the ones that are semi-padded. i got newer ones which were all hard plastic but that ended up pinching a nerve that took 9 months to heal, so i went back to my old semi soft ones.