I had some MCL issues and general knee problems this last fall and early winter. I ended up getting the Asterisk Cell knee braces. I was nervous at first about how much it would help.
They ended up being great! My my knees felt 10x better after a day of skiing vs a neoprene /w metal hinges brace. For the money (I paid 530shipped for the pair from Pittsburghpowersports.com) they exceeded my expectations. They have a knee cap protector (mainly for the moto guys) that is removable, which is what I did and makes them less bulky.
Alot of people rag on knee braces saying they dont really do anything. They definitely help but make sure to continue doing rehab/leg strengthening exercises. Relying on them solely will just lead back to knee problems