A professional fitting would be best, but failing that, give a fit calculator a shot. There are plenty available, but the one at Wrench Science seems decent. It will tell you what your seat height should be and plenty of other stuff.

The saddle itself should not have the means to tilit. All new and decent seatposts have heads that tilt. Loosen the bolt on the seatpost just under the saddle a decent amount and you should be able to slide the seat forward and back and rotate it up and down.

Also, as an assistant in helping your knees get better and keeping them good I would suggest taking Glucosamine and Flax Seed oil. I am 21 and had minor knee problems for the last 10 years or so. When I was 14 I was hit by a van and my right knee was messed up even more, it pretty much got better after a year, but always bugged me a little more than the left. My knees would always ache a bit after physical activity and running especially and my kness also popped a fair amount. About 3 months ago I started taking Glucosamine and Flax Seed oil and I have noticed for the first time in as long as I can remember that I never have knee problems and my knees don't pop anymore. You may want to try theses for a few months at least to get the knees back up to par.