Every once in a while I may be sitting in a chair or kneeling on the floor and all of the sudden one of my knees will seem to "pop" out of its scocket almost like it dislocated. It stings for a while and the muscles and tendons are sore for about a day or so. Or I pedal a bike for a straight minute and my legs feel like they are about to fall apart. This bothers me a lot because I'm 24. I talked to my doctor and he says that the muscles and everything are probably just weak. So I am asking if there is anyone out there who knows something I can do to really strengthen my knees.
I used to have significant problems with my knees when I was younger - a simple game of volleyball would hobble me for a day. My aunt, who is a physical therapist, took a look at me, and suggested that it was a weakness with the muscles that support my kneecap. Since I started lifting weights in the gym, I have had no problems at all. Any kind of exercise at all that works the legs should begin to help. My personal favorite is doing barbell squats, but whatever you have easy access to should help (leg press, leg extension etc..)
Lifting is good, provided it isn't overdone and you maintain good body mechanics while you're at it.
I prefer bodyweight exercises, primarily it's more practical to my needs. If you need a progression to being able to squat (bodyweight/free weights) I cannot recommend "Convict Conditioning" by Paul Wade more highly. It is the single best bodyweight-strength training system I've seen. Demonstrates step by step how to progress to incredible strength, without unnatural movements. Once you have a solid base of functional strength you can progress to whatever you want, my favorite is the kettlebell. Steve Cotter's dvd encyclopedia is tops.
Have you fixed this yet?
I'm suprised your doctor didn't tell you to get exercise and recommend a few. I have had similar problems and my doctor told me to do leg extensions. This is where you sit on the machine with your calves dangling. A bar goes over your shins near the ankle, the bar is attached to weights. You extend your legs, which uses the quadrucep muscles in the front of your upper legs. I will warn you to start with low weights and a lot of repetitions or you will hurt yourself badly! Do not run or ride a bike as you will tear up your knees. If you want to do anything like that either swim or use the eliptical machines as these do not put pressure on your knees. Additional advice would be to do ham curls, which is the opposite of the leg extensions. This will balance your strength in your quads. You can also do calf raises but remember to keep your knees bent otherwise you could damage your knees.