If you haven’t checked it out already, get into Precision Nutrition’s site. They have a ton of information on nutrition and exercise that could be put to good use.
I found this interesting analysis of a paper comparing the efficacy and wear-and-tear effects of the two commonest types of squats (front and back) on the knee joint.
I had already read this paper and the conclusions, but you can go ahead with this article.
The Front Squat is a great exercise alright, but the problem is that you probably need spotters and/or a squat rack if you want to pull heavy. If you don’t have these, you could use a Smith Machine, but this is a poor second, as the machine describes a straight line movement and your core muscles are not put to the test as in the free squats.
The main problem with front squats (when you have good form in it), in my experience, is the inability of the squatter to extend the wrists to the extent needed to hold the weights while going down and coming up. A related problem is the issue of putting the weights back in place once the exercise is done. If you use a crossed grip style, it becomes even more difficult to lay the bar down. Beginners can do front squats with just a barbell or with light dumbbells, but should up the ante soon, as these are the ones where you should hit it hard and heavy to lose that tyre of fat, and get stronger in your legs and back.
Whatever it is, the front squats are great exercises that every person must do, even those (I would even say especially those) who have painful knees.
For a detailed and extremely intelligent analysis of squats, I can’t find one better than the Squatting 101 at Mike Robertson’s site (one of the treasure troves of kinesiology info in the net).