Replying to What's up with my knees?

Ill try to make a short history of whats been going on with my knees, maybe you guys can already tell me whats up with them, before i get some expert advice when i get back home.  Ive already had them checked out by a regular doctor once a few years ago but he didn't seem to think it was very serious.

When I was younger i never worried about hard and/or flat landings or anything, I just did it all and probably didn't land square most of the time, I guess the problems started then.  Back then i was skiing bi-weekly and every time after training my knees were so sore that i had to walk stairs like a 70 year old.

Nowadays i can only go skiing like one or two weeks a year, and never have knee problems when i dont ski.  The only thing noticeable is a loud cracking noise when squating (on the way back up).

So now i'm in Austria for a week and after my first day, no jumps just hard charging and bc, my knees are already starting to complain on the stairs.  Its not really limiting my skiing, but i do notice them a lot when i have to absorb landings or bumps.  They do feel really brittle when im in the slush.  As for jumps i try to stay away from hardpack landings, I can do bc booters with soft landings without a prob but still it will cause my knees to hurt at the end of the day.

So now the question is, whats the most likely diagnose, and whats a possible solution?